Re: [PATCH RFC 3/3] drm/exynos: use pending_components for components tracking

2014-04-26 Thread Russell King - ARM Linux 
On Fri, Apr 25, 2014 at 04:36:01PM +0200, Andrzej Hajda wrote:
 On 04/23/2014 07:13 PM, Russell King - ARM Linux wrote:
  Let me be absolutely clear *why* I'm very interested in this - and that
  is because I'm presently converting TDA998x and Armada DRM to use the
  component helpers.  If your solution is better, then I'd want to convert
  to that instead, and let's retire the component helpers.
  
  At the moment, my belief is that your solution is *very* substandard and
  suboptimal precisely for the reasons I've outlined, especially when it
  comes to sharing a component between several drivers.
  
  So, if you *really* care, you'll stop fobbing me off on this point and
  provide some real technical input how you'd see your solution being used
  in exactly the scenario that I've been outlining several times in this
  thread.
  
  For example, you could show what kind of modifications you expect would
  be required to the _existing_ TDA998x driver to allow it to participate
  as a device declared in DT as an entirely separate entity, probed via the
  standard I2C probing methods, and then hook itself into the appropriate
  DRM driver.  Remembering, of course, that the TDA998x device is used by
  more than _just_ Armada DRM.
  
  I don't care if you show it via pseudo-code or by real patch.  I just
  want to know _how_ your solution could be used.  And I won't want some
  silly remark like trivially or I've already answered that.  I want
  _you_ to _show_ _how_ it can be done.
  
 
 Thats good, constructive discussion is better.

Well, the above is the _same_ fscking question I've been asking you
all along and that you have failed to answer properly until now.
Unfortunately, your reply still doesn't answer my concerns.

 I have no experience with tda998x, armada and drm_encoder_slave, so
 please be kind if I make some mistakes regarding them.
 I will try to show the complete solution starting from the current state
 of tda998x and armada in linux-next. I will present solution for DT as
 it is more standardized than board files. I hope it should not be a
 problem to port it back to board files if necessary.
 
 First I will try to show how to get rid of ifdefs in armada_drv.c, it is
 not a part of my proposition but you have emphasized it.
 
 1. tda998x have already minimal DT support, so we can create proper i2c
 client device node with nxp,tda998x compatible.
 
 2. There are tda998x_encoder_params defined in armada_drv.c they should
 be removed from armada and added to tda998x node, its parsing to tda
 driver should be added as well.
 
 3. In armada_drv.c there is armada_drm_slave_config specific for tda. I
 am not sure of all its content but it seems it could be mapped to DT
 video interface.
 So if in armada_drm node there will be port node it means there
 is something connected to the output and it uses drm_encoder_slave
 interface, if there is no port node there is no encoder.
 Sample bindings:
 
 armada_drm {
   ...
   port {
   drm_ep: endpoint {
   remote-endpoint = tda_ep;
   crtcs = 1;
   poll_connect;
   poll_disconnect;
   interlace_allowed;
   };
   };
 };
 
 ...
 
 i2c_x {
   tda@70 {
   reg = 0x70;
   compatible = nxp,tda998x;
   swap_a = ...;
   swap_b = ...;
   ...
   port {
   endpoint {
   remote-endpoint = drm_ep;
   };
   };
   };
 };
 
 4. In armada_drm call of drm_i2c_encoder_init should be replaced
 by sth like:
   client = of_find_i2c_device_by_node(dev node containing drm_ep phandle);
   device_lock(client-dev);
   if (!client-dev.driver) {
   ret = -EPROBE_DEFER;
   goto unlock;
   }
   module_get(client-dev.driver-owner);
   encoder_drv = 
 to_drm_i2c_encoder_driver(to_i2c_driver(client-dev.driver));
   encoder_drv-encoder_init(client, dev, encoder);
 unlock:
   device_unlock(client-dev);
 
 Similar change should be done to destroy code.
 Of course please consider this code as a draft.

This looks reasonable - and I'm sure we can easily work around the
situation when there's no i2c encoder.  There is one thing which concerns
me about the above - that module_get() call.  module_get() only saves you
from the module being unloaded, which really isn't an issue if the
problem with the device going away is solved.

If you think about this for a moment, you'll understand why - in order for
the module to be unloaded, the device driver must be first unbound from
any devices.  So:

(a) you need to prevent the device driver being unbound while the DRM device
is being brought up, and
(b) you need to bring the DRM device down if the device driver is unbound.

Those are the two difficult problems which need solving.

The other thing which I

Re: [PATCH RFC 3/3] drm/exynos: use pending_components for components tracking

2014-04-25 Thread Andrzej Hajda 
On 04/23/2014 07:13 PM, Russell King - ARM Linux wrote:
 On Wed, Apr 23, 2014 at 05:43:28PM +0100, Russell King - ARM Linux wrote:
 So, maybe you would like to finally address *my* point about TDA998x
 and your solution in a way that provides a satisfactory answer.  *Show*
 how it can be done, or *outline* how it can be done.
 
 Let me be absolutely clear *why* I'm very interested in this - and that
 is because I'm presently converting TDA998x and Armada DRM to use the
 component helpers.  If your solution is better, then I'd want to convert
 to that instead, and let's retire the component helpers.
 
 At the moment, my belief is that your solution is *very* substandard and
 suboptimal precisely for the reasons I've outlined, especially when it
 comes to sharing a component between several drivers.
 
 So, if you *really* care, you'll stop fobbing me off on this point and
 provide some real technical input how you'd see your solution being used
 in exactly the scenario that I've been outlining several times in this
 thread.
 
 For example, you could show what kind of modifications you expect would
 be required to the _existing_ TDA998x driver to allow it to participate
 as a device declared in DT as an entirely separate entity, probed via the
 standard I2C probing methods, and then hook itself into the appropriate
 DRM driver.  Remembering, of course, that the TDA998x device is used by
 more than _just_ Armada DRM.
 
 I don't care if you show it via pseudo-code or by real patch.  I just
 want to know _how_ your solution could be used.  And I won't want some
 silly remark like trivially or I've already answered that.  I want
 _you_ to _show_ _how_ it can be done.
 

Thats good, constructive discussion is better.

I have no experience with tda998x, armada and drm_encoder_slave, so
please be kind if I make some mistakes regarding them.
I will try to show the complete solution starting from the current state
of tda998x and armada in linux-next. I will present solution for DT as
it is more standardized than board files. I hope it should not be a
problem to port it back to board files if necessary.

First I will try to show how to get rid of ifdefs in armada_drv.c, it is
not a part of my proposition but you have emphasized it.

1. tda998x have already minimal DT support, so we can create proper i2c
client device node with nxp,tda998x compatible.

2. There are tda998x_encoder_params defined in armada_drv.c they should
be removed from armada and added to tda998x node, its parsing to tda
driver should be added as well.

3. In armada_drv.c there is armada_drm_slave_config specific for tda. I
am not sure of all its content but it seems it could be mapped to DT
video interface.
So if in armada_drm node there will be port node it means there
is something connected to the output and it uses drm_encoder_slave
interface, if there is no port node there is no encoder.
Sample bindings:

armada_drm {
...
port {
drm_ep: endpoint {
remote-endpoint = tda_ep;
crtcs = 1;
poll_connect;
poll_disconnect;
interlace_allowed;
};
};
};

...

i2c_x {
tda@70 {
reg = 0x70;
compatible = nxp,tda998x;
swap_a = ...;
swap_b = ...;
...
port {
endpoint {
remote-endpoint = drm_ep;
};
};
};
};

4. In armada_drm call of drm_i2c_encoder_init should be replaced
by sth like:
client = of_find_i2c_device_by_node(dev node containing drm_ep phandle);
device_lock(client-dev);
if (!client-dev.driver) {
ret = -EPROBE_DEFER;
goto unlock;
}
module_get(client-dev.driver-owner);
encoder_drv = 
to_drm_i2c_encoder_driver(to_i2c_driver(client-dev.driver));
encoder_drv-encoder_init(client, dev, encoder);
unlock:
device_unlock(client-dev);

Similar change should be done to destroy code.
Of course please consider this code as a draft.

All the above is just for removing ifdefs from armada_drv.c, it
is not really connected with my proposition.

It is not really safe, and I am not sure where exactly the locking
should be performed. For sure it can crash when unbind will be called
via sysfs property, but it seems at least as safe as
drm_i2c_encoder_init or it should be possible to make it such.
And it allows to attach to armada theoretically any hardware compatible
encoder having drm_i2c_encoder interface.

What do you think about above steps? Is it OK for you?

And now about my proposition for device probe order issue. My first
answer to your objections about 'glue problem' was to make global list
of 'ready' devices instead of the one glued to the main drm driver.
Over time my idea evolved.
My

Re: [PATCH RFC 3/3] drm/exynos: use pending_components for components tracking

2014-04-23 Thread Andrzej Hajda 
On 04/22/2014 01:51 PM, Russell King - ARM Linux wrote:
 On Tue, Apr 22, 2014 at 01:29:54PM +0200, Andrzej Hajda wrote:
 On 04/18/2014 02:46 PM, Russell King - ARM Linux wrote:
 On Fri, Apr 18, 2014 at 02:02:37PM +0200, Andrzej Hajda wrote:
 Separation of the interfaces exposed by the device from the device itself
 seems to me a good thing. I would even consider it as a biggest
 advantage of this solution :)

 The problem of re-initialization does not seems to be relevant here, it
 is classic
 problem of coding correctness nothing more, it can appear here and in
 many different
 places.
 It may be a problem of coding correctless, but it's also a maintainability
 problem too - it makes it _much_ more difficult to ensure that everything
 is correct.
 But forcibly re-initializing all component devices instead of fixing bugs
 in specific drivers seems to be 'absolutely absurd' as classic says.
 They're *unnecessary* bugs that wouldn't even exist if it weren't for
 the forced-splitup of the initialisation into two separate parts that
 your approach mandates.

 Yes, I know that you're desperate to play that down, but you can't get

Not true. I only try to find the best solution and the approach with
multiple re-probing just to avoid potential bugs in drivers does not
look to me correct.

 away from this fact: your approach _forces_ a split up of the
 initialisation into dependent two stages and that fact _alone_ adds
 additional complexity, and along with that additional complexity comes
 more opportunity for bugs. 

This sound so funny, just look at componentize patches - every patch
adds two stage initialization for every component and the master,
with forced unwinding and two levels of devres management.

'My approach' adds only one call to probe and one call to remove of
components,
and very simple and straightforward interface to the master.

'My approach' is very standard - during probe driver probes hardware,
and registers interfaces which can be used by other drivers, for example
by drm master. The only addition is reporting its readiness. Comparing to
'your approach' it is bloody simple.


  Also with that additional complexity comes
 the need to perform more tests to find those bugs, and given that most
 people just say okay, it boots and seems to work, that's good enough
 for me there is a high possibility that these kinds of bugs will take
 a long time to find.

Volume of changes for each component and drm device management
dispersed on all components makes your argument very valid for
component subsystem.

Btw have you observed component framework when one of the components
during bind returns -EPROBE_DEFER ? In my tests it resulted in
deferred probing of master and unbind/bind of other components.
So lets say you have N components and the last component will be deferred
K times, it results in:
- K times deferring of the last component and the master,
- (N - 1) * K - unbinds and binds of other components.



 As I wrote already, this framework was proposed for drivers which
 are tied together anyway, and this is case of many drivers, not
 only exynos.
 Please name them.

 Standalone drivers were not at my sight but I have also described in
 other mail how the framework can be 'improved' to support standalone
 drivers also.
 At the moment, I don't see a justification for your simplified
 and restrictive solution, which if used will lock drivers into that
 simplisitic method, and which can't ever be extended without lots of
 ifdeffery to having other components (such as TDA998x) attached.

 My objections are entirely based on where imx-drm and armada DRM are
 going, neither of which could ever use your implementation.

 Before you say that it isn't meant to deal with stuff like the TDA998x,
 take a moment to think about this - the Dove video subsystem was
 designed to support OLPC.  It was primerly designed to drive a LCD
 screen plus an on-board VGA DAC.  Everything for that is on-SoC.  With
 that, the hardware is well known, and your solution could be used.

 However, then SolidRun came along and dropped a TDA998x on the LCD output
 pins.  Suddenly, things aren't that simple, and your solution falls
 apart, because it can't cope with a generic component that has no knowledge
 of the rest of its master.

 This kind of scenario can happen /any/ time, and any time it does happen,
 your simple solution falls apart.

I think I have answered you two or three times that it is not a problem
to remove
'glued drivers' restriction. I desperately try to avoid accusing you for
'desperately
playing down' on this subject, so I will not comment this anymore.

On the other hand you have not answered quite important question - how
do you plan to componentize drivers shared by different drms when
one of drms is not componentized???


Regards
Andrzej

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Re: [PATCH RFC 3/3] drm/exynos: use pending_components for components tracking

2014-04-23 Thread Russell King - ARM Linux 
On Wed, Apr 23, 2014 at 05:04:46PM +0200, Andrzej Hajda wrote:
 On 04/22/2014 01:51 PM, Russell King - ARM Linux wrote:
  Yes, I know that you're desperate to play that down, but you can't get
 
 Not true. I only try to find the best solution and the approach with
 multiple re-probing just to avoid potential bugs in drivers does not
 look to me correct.
 
  away from this fact: your approach _forces_ a split up of the
  initialisation into dependent two stages and that fact _alone_ adds
  additional complexity, and along with that additional complexity comes
  more opportunity for bugs. 
 
 This sound so funny, just look at componentize patches - every patch
 adds two stage initialization for every component and the master,
 with forced unwinding and two levels of devres management.

*Sigh*.  Why am I bothering discussing this with you.

*NO* it does not, for the VERY SIMPLE reason that NOTHING is done before
the BIND.  NO structures are allocated.  NOTHING is setup.  The *only*
thing that is done is the driver registers with the component helper.

That's not two stage initialisation.  That's *single* stage.

 'My approach' adds only one call to probe and one call to remove of
 components, and very simple and straightforward interface to the master.

You're talking utter garbage there.

 'My approach' is very standard - during probe driver probes hardware,
 and registers interfaces which can be used by other drivers, for example
 by drm master. The only addition is reporting its readiness. Comparing to
 'your approach' it is bloody simple.

More unbelievable crap.

   Also with that additional complexity comes
  the need to perform more tests to find those bugs, and given that most
  people just say okay, it boots and seems to work, that's good enough
  for me there is a high possibility that these kinds of bugs will take
  a long time to find.
 
 Volume of changes for each component and drm device management
 dispersed on all components makes your argument very valid for
 component subsystem.
 
 Btw have you observed component framework when one of the components
 during bind returns -EPROBE_DEFER ? In my tests it resulted in
 deferred probing of master and unbind/bind of other components.
 So lets say you have N components and the last component will be deferred
 K times, it results in:
 - K times deferring of the last component and the master,
 - (N - 1) * K - unbinds and binds of other components.

True, and you can't get away from that with proper behaviour.

  As I wrote already, this framework was proposed for drivers which
  are tied together anyway, and this is case of many drivers, not
  only exynos.
  Please name them.

You ignored this.  Therefore, I assume that you *can't* name them because
there *aren't* any.  I called your bluff, I win.

  At the moment, I don't see a justification for your simplified
  and restrictive solution, which if used will lock drivers into that
  simplisitic method, and which can't ever be extended without lots of
  ifdeffery to having other components (such as TDA998x) attached.
 
  My objections are entirely based on where imx-drm and armada DRM are
  going, neither of which could ever use your implementation.
 
  Before you say that it isn't meant to deal with stuff like the TDA998x,
  take a moment to think about this - the Dove video subsystem was
  designed to support OLPC.  It was primerly designed to drive a LCD
  screen plus an on-board VGA DAC.  Everything for that is on-SoC.  With
  that, the hardware is well known, and your solution could be used.
 
  However, then SolidRun came along and dropped a TDA998x on the LCD output
  pins.  Suddenly, things aren't that simple, and your solution falls
  apart, because it can't cope with a generic component that has no knowledge
  of the rest of its master.
 
  This kind of scenario can happen /any/ time, and any time it does happen,
  your simple solution falls apart.
 
 I think I have answered you two or three times that it is not a problem
 to remove
 'glued drivers' restriction. I desperately try to avoid accusing you for
 'desperately
 playing down' on this subject, so I will not comment this anymore.

Right, so what I draw from this is that *you* again refuse to answer this
point because despite your assertions that your solution can do it, you
have no clue as to *how* it can be done.  I've looked at your solution
with respect to this, and I *can't* see how it can be done either.  That's
why I've been asking *you* the question, so that *you* can provide some
technical input to it.

 On the other hand you have not answered quite important question - how
 do you plan to componentize drivers shared by different drms when
 one of drms is not componentized???

Read this, from a message I sent at the beginning of February:
| Here's my changes to the TDA998x driver to add support for the component
| helper.  The TDA998x driver retains support for the old way so that
| drivers can be transitioned.  For any one DRM

Re: [PATCH RFC 3/3] drm/exynos: use pending_components for components tracking

2014-04-23 Thread Russell King - ARM Linux 
On Wed, Apr 23, 2014 at 05:43:28PM +0100, Russell King - ARM Linux wrote:
 So, maybe you would like to finally address *my* point about TDA998x
 and your solution in a way that provides a satisfactory answer.  *Show*
 how it can be done, or *outline* how it can be done.

Let me be absolutely clear *why* I'm very interested in this - and that
is because I'm presently converting TDA998x and Armada DRM to use the
component helpers.  If your solution is better, then I'd want to convert
to that instead, and let's retire the component helpers.

At the moment, my belief is that your solution is *very* substandard and
suboptimal precisely for the reasons I've outlined, especially when it
comes to sharing a component between several drivers.

So, if you *really* care, you'll stop fobbing me off on this point and
provide some real technical input how you'd see your solution being used
in exactly the scenario that I've been outlining several times in this
thread.

For example, you could show what kind of modifications you expect would
be required to the _existing_ TDA998x driver to allow it to participate
as a device declared in DT as an entirely separate entity, probed via the
standard I2C probing methods, and then hook itself into the appropriate
DRM driver.  Remembering, of course, that the TDA998x device is used by
more than _just_ Armada DRM.

I don't care if you show it via pseudo-code or by real patch.  I just
want to know _how_ your solution could be used.  And I won't want some
silly remark like trivially or I've already answered that.  I want
_you_ to _show_ _how_ it can be done.

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Re: [PATCH RFC 3/3] drm/exynos: use pending_components for components tracking

2014-04-22 Thread Andrzej Hajda 
Hi Russel,

My answer little bit later due to Easter.

On 04/18/2014 02:42 PM, Russell King - ARM Linux wrote:
 On Fri, Apr 18, 2014 at 01:27:53PM +0200, Andrzej Hajda wrote:
 Hi Russel,

 Thanks for comments.

 On 04/17/2014 11:47 PM, Russell King - ARM Linux wrote:
 On Thu, Apr 17, 2014 at 01:28:50PM +0200, Andrzej Hajda wrote:
 +out:
 +  if (ret != -EPROBE_DEFER)
 +  exynos_drm_dev_ready(pdev-dev);
 So we end up with everyone needing a ready call in each sub-driver
 back into the main driver... this makes it impossible to write a
 generic subcomponent driver which is not tied in any way to the
 main driver.

 That is quite some restriction, and would prevent, for example, the
 TDA998x driver being used both with Armada DRM, tilcdc and any other
 driver.
 As I see in armada driver drm is deferred in case tda998x is not yet
 available. The same solution can be still used with pending_devices
 approach - the main driver will not report its readiness until tda998x
 is present.

 Anyway it still seems to be better than componentize every driver which can
 probably become a part of some superdevice.

 If you want to get rid of deferred probe one can make global list of
 'ready' devices with notifications systems for master devices.

 Maybe it would be good to consider notification system for devices probe
 result,
 it will require that driver register all its interfaces in probe, ie its
 readiness cannot
 be reported later but will not require to add new framework. I hope just
 extending current
 notification system should be enough.
 You aren't addressing my point.  If I were to convert tda998x to use
 your infrastructure, then I would have to add in ifdefs to tie it into
 armada DRM _and_ a different set of ifdefs to tie it into tilcdc.  Then
 when someone else wanted to use it in their driver, they'd have to add
 yet more ifdefs into it to tie it into their driver.

 This does not scale.

As I already answered, you should not use 'my' framework for tda998x
driver, you can still use current approach with deferred probe. I am not
sure
why have you used ifdefs in armada, tilcdc also uses tda998x and without
ifdefs.

'My' framework (I think helper library is a better name) was created to
use with
devices which are closely tied together by another framework - case
of some SoC devices.



 So, please address my point: in your system, how can a single component
 be shared between multiple different master drivers?


I have answered this question above, again. But your question suggests
you want to componentize
also drivers which are shared by different DRMs. How do you want to do it?
- componentize all DRM drivers sharing given driver?
- componentize shared device in a way that it can used by
non-componentized devices? how? I guess it
will be possible but will have some price.

Regards
Andrzej



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Re: [PATCH RFC 3/3] drm/exynos: use pending_components for components tracking

2014-04-22 Thread Andrzej Hajda 
On 04/18/2014 02:46 PM, Russell King - ARM Linux wrote:
 On Fri, Apr 18, 2014 at 02:02:37PM +0200, Andrzej Hajda wrote:
 Separation of the interfaces exposed by the device from the device itself
 seems to me a good thing. I would even consider it as a biggest
 advantage of this solution :)

 The problem of re-initialization does not seems to be relevant here, it
 is classic
 problem of coding correctness nothing more, it can appear here and in
 many different
 places.
 It may be a problem of coding correctless, but it's also a maintainability
 problem too - it makes it _much_ more difficult to ensure that everything
 is correct.

But forcibly re-initializing all component devices instead of fixing bugs
in specific drivers seems to be 'absolutely absurd' as classic says.
 Anyway it seems we have different point of view on the problem, your say
 about devices with two stage initialization. I see it more as devices
 registering interfaces and superdevice using it.
 Right, so please make this exynos-specific, because from what I can see it
 has no reason to pretend to be generic.  As I've already pointed out, it
 can't be used in the general case because it ties sub-components directly
 to their main driver, which is absolutely absurd.  Please keep this
 absurdness in exynos and don't spread it around.  Thanks.

As I wrote already, this framework was proposed for drivers which
are tied together anyway, and this is case of many drivers, not only exynos.
Standalone drivers were not at my sight but I have also described in
other mail
how the framework can be 'improved' to support standalone drivers also.

Regards
Andrzej



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Re: [PATCH RFC 3/3] drm/exynos: use pending_components for components tracking

2014-04-22 Thread Russell King - ARM Linux 
On Tue, Apr 22, 2014 at 01:29:54PM +0200, Andrzej Hajda wrote:
 On 04/18/2014 02:46 PM, Russell King - ARM Linux wrote:
  On Fri, Apr 18, 2014 at 02:02:37PM +0200, Andrzej Hajda wrote:
  Separation of the interfaces exposed by the device from the device itself
  seems to me a good thing. I would even consider it as a biggest
  advantage of this solution :)
 
  The problem of re-initialization does not seems to be relevant here, it
  is classic
  problem of coding correctness nothing more, it can appear here and in
  many different
  places.
  It may be a problem of coding correctless, but it's also a maintainability
  problem too - it makes it _much_ more difficult to ensure that everything
  is correct.
 
 But forcibly re-initializing all component devices instead of fixing bugs
 in specific drivers seems to be 'absolutely absurd' as classic says.

They're *unnecessary* bugs that wouldn't even exist if it weren't for
the forced-splitup of the initialisation into two separate parts that
your approach mandates.

Yes, I know that you're desperate to play that down, but you can't get
away from this fact: your approach _forces_ a split up of the
initialisation into dependent two stages and that fact _alone_ adds
additional complexity, and along with that additional complexity comes
more opportunity for bugs.  Also with that additional complexity comes
the need to perform more tests to find those bugs, and given that most
people just say okay, it boots and seems to work, that's good enough
for me there is a high possibility that these kinds of bugs will take
a long time to find.

 As I wrote already, this framework was proposed for drivers which
 are tied together anyway, and this is case of many drivers, not
 only exynos.

Please name them.

 Standalone drivers were not at my sight but I have also described in
 other mail how the framework can be 'improved' to support standalone
 drivers also.

At the moment, I don't see a justification for your simplified
and restrictive solution, which if used will lock drivers into that
simplisitic method, and which can't ever be extended without lots of
ifdeffery to having other components (such as TDA998x) attached.

My objections are entirely based on where imx-drm and armada DRM are
going, neither of which could ever use your implementation.

Before you say that it isn't meant to deal with stuff like the TDA998x,
take a moment to think about this - the Dove video subsystem was
designed to support OLPC.  It was primerly designed to drive a LCD
screen plus an on-board VGA DAC.  Everything for that is on-SoC.  With
that, the hardware is well known, and your solution could be used.

However, then SolidRun came along and dropped a TDA998x on the LCD output
pins.  Suddenly, things aren't that simple, and your solution falls
apart, because it can't cope with a generic component that has no knowledge
of the rest of its master.

This kind of scenario can happen /any/ time, and any time it does happen,
your simple solution falls apart.

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Re: [PATCH RFC 3/3] drm/exynos: use pending_components for components tracking

2014-04-18 Thread Andrzej Hajda 
On 04/18/2014 12:04 AM, Russell King - ARM Linux wrote:
 On Thu, Apr 17, 2014 at 01:28:50PM +0200, Andrzej Hajda wrote:
 +static int exynos_drm_add_blocker(struct device *dev, void *data)
 +{
 +struct device_driver *drv = data;
 +
 +if (!platform_bus_type.match(dev, drv))
 +return 0;
 +
 +device_lock(dev);
 +if (!dev-driver)
 +exynos_drm_dev_busy(dev);
 +device_unlock(dev);
 +
 +return 0;
 +}
 +
 +static void exynos_drm_init_blockers(struct device_driver *drv)
 +{
 +bus_for_each_dev(platform_bus_type, NULL, drv, exynos_drm_add_blocker);
 +}
 This feels very wrong to be dumping the above code into every driver which
 wants to make use of some kind of componentised support.

 You also appear to need to know the struct device_driver's for every
 component.  While that may work for exynos, it doesn't work elsewhere
 where the various components of the system are very real separate
 kernel modules - for example, a separate I2C driver such as the TDA998x
 case I mentioned in my first reply.

 I can't see how your solution would be usable in that circumstance.

It is up to the master driver how it want to create list of required
devices,
this is why I put it into exynos_drm and not into the framework.
You can use superdevice DT node for it, fixed list whatever you want.
It is not a part of the framework, it is just part of exynos_drm specific
implementation.
Component framework also does not provide mechanism for it.

Regarding TDA998x I have replied in the previous e-mail.


 The third issue I have is that you're still needing to have internal
 exynos sub-device management - you're having to add the individual
 devices to some kind of list, array or static data, and during DRM
 probe you're having to then walk these lists/arrays/static data to
 locate these sub-devices and finish each of their individual
 initialisations.  So you're ending up with a two-tier initialisation.

 That's not particularly good because it means you're exposed to
 problems where the state is different between two initialisations -
 when the device is recreated, your component attempts to re-finalise
 the initialisation a second time.  It wouldn't take much for a field
 to be assumed to be zero at init time somewhere for a bug to creep
 in.


Separation of the interfaces exposed by the device from the device itself
seems to me a good thing. I would even consider it as a biggest
advantage of this solution :)

The problem of re-initialization does not seems to be relevant here, it
is classic
problem of coding correctness nothing more, it can appear here and in
many different
places.

Anyway it seems we have different point of view on the problem, your say
about
devices with two stage initialization. I see it more as devices
registering interfaces and superdevice
using it.

Regards
Andrzej





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Re: [PATCH RFC 3/3] drm/exynos: use pending_components for components tracking

2014-04-18 Thread Russell King - ARM Linux 
On Fri, Apr 18, 2014 at 01:27:53PM +0200, Andrzej Hajda wrote:
 Hi Russel,
 
 Thanks for comments.
 
 On 04/17/2014 11:47 PM, Russell King - ARM Linux wrote:
  On Thu, Apr 17, 2014 at 01:28:50PM +0200, Andrzej Hajda wrote:
  +out:
  +  if (ret != -EPROBE_DEFER)
  +  exynos_drm_dev_ready(pdev-dev);
  So we end up with everyone needing a ready call in each sub-driver
  back into the main driver... this makes it impossible to write a
  generic subcomponent driver which is not tied in any way to the
  main driver.
 
  That is quite some restriction, and would prevent, for example, the
  TDA998x driver being used both with Armada DRM, tilcdc and any other
  driver.
 
 As I see in armada driver drm is deferred in case tda998x is not yet
 available. The same solution can be still used with pending_devices
 approach - the main driver will not report its readiness until tda998x
 is present.
 
 Anyway it still seems to be better than componentize every driver which can
 probably become a part of some superdevice.
 
 If you want to get rid of deferred probe one can make global list of
 'ready' devices with notifications systems for master devices.
 
 Maybe it would be good to consider notification system for devices probe
 result,
 it will require that driver register all its interfaces in probe, ie its
 readiness cannot
 be reported later but will not require to add new framework. I hope just
 extending current
 notification system should be enough.

You aren't addressing my point.  If I were to convert tda998x to use
your infrastructure, then I would have to add in ifdefs to tie it into
armada DRM _and_ a different set of ifdefs to tie it into tilcdc.  Then
when someone else wanted to use it in their driver, they'd have to add
yet more ifdefs into it to tie it into their driver.

This does not scale.

So, please address my point: in your system, how can a single component
be shared between multiple different master drivers?

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Re: [PATCH RFC 3/3] drm/exynos: use pending_components for components tracking

2014-04-18 Thread Russell King - ARM Linux 
On Fri, Apr 18, 2014 at 02:02:37PM +0200, Andrzej Hajda wrote:
 Separation of the interfaces exposed by the device from the device itself
 seems to me a good thing. I would even consider it as a biggest
 advantage of this solution :)
 
 The problem of re-initialization does not seems to be relevant here, it
 is classic
 problem of coding correctness nothing more, it can appear here and in
 many different
 places.

It may be a problem of coding correctless, but it's also a maintainability
problem too - it makes it _much_ more difficult to ensure that everything
is correct.

 Anyway it seems we have different point of view on the problem, your say
 about devices with two stage initialization. I see it more as devices
 registering interfaces and superdevice using it.

Right, so please make this exynos-specific, because from what I can see it
has no reason to pretend to be generic.  As I've already pointed out, it
can't be used in the general case because it ties sub-components directly
to their main driver, which is absolutely absurd.  Please keep this
absurdness in exynos and don't spread it around.  Thanks.

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[PATCH RFC 3/3] drm/exynos: use pending_components for components tracking

2014-04-17 Thread Andrzej Hajda 
exynos_drm is composed from multiple devices which provides different
interfaces. To properly start/stop drm master device it should track
readiness of all its components. This patch uses pending_components
framework to perform this task.
On module initialization before component driver registration all devices
matching drivers are added to pending_components. Drivers during probe
are removed from the list unless deferred probe happens. When list becomes
empty callback is fired to start drm master. Later if any device adds itself
to the list callback is fired to stop drm master.

The core of the changes is in exynos_drm_drv.c. Driver modifications are
limited only to signal its readiness in probe and remove driver callbacks.

Signed-off-by: Andrzej Hajda a.ha...@samsung.com
---
 drivers/gpu/drm/exynos/Kconfig  |  1 +
 drivers/gpu/drm/exynos/exynos_dp_core.c | 36 +++--
 drivers/gpu/drm/exynos/exynos_drm_drv.c | 61 +++--
 drivers/gpu/drm/exynos/exynos_drm_drv.h |  3 ++
 drivers/gpu/drm/exynos/exynos_drm_dsi.c | 41 +++
 drivers/gpu/drm/exynos/exynos_drm_fimc.c| 34 ++--
 drivers/gpu/drm/exynos/exynos_drm_fimd.c| 37 +++--
 drivers/gpu/drm/exynos/exynos_drm_g2d.c | 17 ++--
 drivers/gpu/drm/exynos/exynos_drm_gsc.c | 30 +-
 drivers/gpu/drm/exynos/exynos_drm_ipp.c | 18 ++---
 drivers/gpu/drm/exynos/exynos_drm_rotator.c | 27 +
 drivers/gpu/drm/exynos/exynos_drm_vidi.c| 16 +---
 drivers/gpu/drm/exynos/exynos_hdmi.c| 53 +
 drivers/gpu/drm/exynos/exynos_mixer.c   | 13 --
 14 files changed, 278 insertions(+), 109 deletions(-)

diff --git a/drivers/gpu/drm/exynos/Kconfig b/drivers/gpu/drm/exynos/Kconfig
index 5bf5bca..4ed8eb2 100644
--- a/drivers/gpu/drm/exynos/Kconfig
+++ b/drivers/gpu/drm/exynos/Kconfig
@@ -8,6 +8,7 @@ config DRM_EXYNOS
select FB_CFB_IMAGEBLIT
select VT_HW_CONSOLE_BINDING if FRAMEBUFFER_CONSOLE
select VIDEOMODE_HELPERS
+   select PENDING_COMPONENTS
help
  Choose this option if you have a Samsung SoC EXYNOS chipset.
  If M is selected the module will be called exynosdrm.
diff --git a/drivers/gpu/drm/exynos/exynos_dp_core.c 
b/drivers/gpu/drm/exynos/exynos_dp_core.c
index 9385e96..24f5c98 100644
--- a/drivers/gpu/drm/exynos/exynos_dp_core.c
+++ b/drivers/gpu/drm/exynos/exynos_dp_core.c
@@ -1240,29 +1240,32 @@ static int exynos_dp_probe(struct platform_device *pdev)
dp = devm_kzalloc(pdev-dev, sizeof(struct exynos_dp_device),
GFP_KERNEL);
if (!dp) {
-   dev_err(pdev-dev, no memory for device data\n);
-   return -ENOMEM;
+   ret = -ENOMEM;
+   goto out;
}
 
dp-dev = pdev-dev;
dp-dpms_mode = DRM_MODE_DPMS_OFF;
 
dp-video_info = exynos_dp_dt_parse_pdata(pdev-dev);
-   if (IS_ERR(dp-video_info))
-   return PTR_ERR(dp-video_info);
+   if (IS_ERR(dp-video_info)) {
+   ret = PTR_ERR(dp-video_info);
+   goto out;
+   }
 
ret = exynos_dp_dt_parse_phydata(dp);
if (ret)
-   return ret;
+   goto out;
 
ret = exynos_dp_dt_parse_panel(dp);
if (ret)
-   return ret;
+   goto out;
 
dp-clock = devm_clk_get(pdev-dev, dp);
if (IS_ERR(dp-clock)) {
dev_err(pdev-dev, failed to get clock\n);
-   return PTR_ERR(dp-clock);
+   ret = PTR_ERR(dp-clock);
+   goto out;
}
 
clk_prepare_enable(dp-clock);
@@ -1270,13 +1273,16 @@ static int exynos_dp_probe(struct platform_device *pdev)
res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 
dp-reg_base = devm_ioremap_resource(pdev-dev, res);
-   if (IS_ERR(dp-reg_base))
-   return PTR_ERR(dp-reg_base);
+   if (IS_ERR(dp-reg_base)) {
+   ret = PTR_ERR(dp-reg_base);
+   goto out;
+   }
 
dp-irq = platform_get_irq(pdev, 0);
if (dp-irq == -ENXIO) {
dev_err(pdev-dev, failed to get irq\n);
-   return -ENODEV;
+   ret = -ENODEV;
+   goto out;
}
 
INIT_WORK(dp-hotplug_work, exynos_dp_hotplug);
@@ -1289,7 +1295,7 @@ static int exynos_dp_probe(struct platform_device *pdev)
exynos-dp, dp);
if (ret) {
dev_err(pdev-dev, failed to request irq\n);
-   return ret;
+   goto out;
}
disable_irq(dp-irq);
 
@@ -1298,13 +1304,19 @@ static int exynos_dp_probe(struct platform_device *pdev)
platform_set_drvdata(pdev, exynos_dp_display);
exynos_drm_display_register(exynos_dp_display);
 
-   return 0;
+out:
+   if (ret != -EPROBE_DEFER)
+

Re: [PATCH RFC 3/3] drm/exynos: use pending_components for components tracking

2014-04-17 Thread Russell King - ARM Linux 
On Thu, Apr 17, 2014 at 01:28:50PM +0200, Andrzej Hajda wrote:
 +out:
 + if (ret != -EPROBE_DEFER)
 + exynos_drm_dev_ready(pdev-dev);

So we end up with everyone needing a ready call in each sub-driver
back into the main driver... this makes it impossible to write a
generic subcomponent driver which is not tied in any way to the
main driver.

That is quite some restriction, and would prevent, for example, the
TDA998x driver being used both with Armada DRM, tilcdc and any other
driver.

So, while your solution may work for exynos, it's not suitable for
general use.

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Re: [PATCH RFC 3/3] drm/exynos: use pending_components for components tracking

2014-04-17 Thread Russell King - ARM Linux 
On Thu, Apr 17, 2014 at 01:28:50PM +0200, Andrzej Hajda wrote:
 +static int exynos_drm_add_blocker(struct device *dev, void *data)
 +{
 + struct device_driver *drv = data;
 +
 + if (!platform_bus_type.match(dev, drv))
 + return 0;
 +
 + device_lock(dev);
 + if (!dev-driver)
 + exynos_drm_dev_busy(dev);
 + device_unlock(dev);
 +
 + return 0;
 +}
 +
 +static void exynos_drm_init_blockers(struct device_driver *drv)
 +{
 + bus_for_each_dev(platform_bus_type, NULL, drv, exynos_drm_add_blocker);
 +}

This feels very wrong to be dumping the above code into every driver which
wants to make use of some kind of componentised support.

You also appear to need to know the struct device_driver's for every
component.  While that may work for exynos, it doesn't work elsewhere
where the various components of the system are very real separate
kernel modules - for example, a separate I2C driver such as the TDA998x
case I mentioned in my first reply.

I can't see how your solution would be usable in that circumstance.

The third issue I have is that you're still needing to have internal
exynos sub-device management - you're having to add the individual
devices to some kind of list, array or static data, and during DRM
probe you're having to then walk these lists/arrays/static data to
locate these sub-devices and finish each of their individual
initialisations.  So you're ending up with a two-tier initialisation.

That's not particularly good because it means you're exposed to
problems where the state is different between two initialisations -
when the device is recreated, your component attempts to re-finalise
the initialisation a second time.  It wouldn't take much for a field
to be assumed to be zero at init time somewhere for a bug to creep
in.

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improving, and getting towards what was expected from it.
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