[PATCH] drm/i915/hdmi: Fix weak connector detection

2016-04-14 Thread Ezequiel Garcia 
On 5 April 2016 at 11:54, Ezequiel Garcia  
wrote:
> (Adding Jani again, who got dropped for some reason)
>
> On 1 April 2016 at 16:50, Ezequiel Garcia  
> wrote:
>> On 01 Apr 06:46 PM, Ville Syrjälä wrote:
>>> On Fri, Apr 01, 2016 at 12:38:11PM -0300, Ezequiel Garcia wrote:
>>> > El abr. 1, 2016 11:47 AM, "Ville Syrjälä" >> > linux.intel.com>
>>> > escribió:
>>> > >
>>> > > On Thu, Mar 31, 2016 at 05:55:03PM -0300, Ezequiel Garcia wrote:
>>> > > > Currently, our implementation of drm_connector_funcs.detect is
>>> > > > based on getting a valid EDID.
>>> > > >
>>> > > > This requirement makes the driver fail to detect connected
>>> > > > connectors in case of EDID corruption, which prevents from falling
>>> > > > back to modes provided by builtin or user-provided EDIDs.
>>> > >
>>> > > So why are you getting corrupted EDIDs?
>>> > >
>>> >
>>> > Does it matter?
>>>
>>> Yes. We should fix the real cause (if possible) instead of adding
>>> more duct tape.
>>>
>>
>> So, there are two things involved in this patch:
>>
>> 1.
>> There are several reasons why EDID can get screwed, this is
>> documented at length [1], and it's the motivation for
>> CONFIG_DRM_LOAD_EDID_FIRMWARE to exist.
>>
>> You can find lots of reports on the internet of people getting
>> corrupt EDID from their monitors. For instance, here's one [2].
>>
>> And even if no firmware is provided using CONFIG_DRM_LOAD_EDID_FIRMWARE,
>> the DRM core will provide a 1024x768 fallback mode:
>>
>> int drm_helper_probe_single_connector_modes(struct drm_connector *connector,
>> uint32_t maxX, uint32_t maxY)
>> {
>> [..]
>> if (count == 0 && connector->status == connector_status_connected)
>> count = drm_add_modes_noedid(connector, 1024, 768);
>>
>> But, this only works if the connector is detected.
>>
>> Since I'm interested in backporting this patch to apply it on the kernels
>> I maintain (which are currently deployed on hundreds of machines), I tried
>> to find a simple solution. Hence, this patch.
>>
>> There's no issue to fix here, because broken hardware is a fact of life,
>> and not something we can fix or ignore [3].
>>
>> 2.
>> On the other side, the i915 implementation looks suspicious. IMHO,
>> drm_connector_funcs.detect should not try to read a valid EDID,
>> and just try to detect if the connector is connected or disconnected.
>>
>> The EDID can be read in drm_connector_helper_funcs.get_modes, as other
>> drm/connector drivers are doing (tda998x, tfp410, tegra).
>>
>> However, I think it's safer to get a simple fix now, and do this
>> as follow-up patches.
>>
>> How does it sound?
>>

Are there any other comments regarding this patch?

If at all possible, I'd like to see this merged, or otherwise
a proposal for an alternative solution.

>> [1] Documentation/EDID/HOWTO.txt
>> [2] 
>> http://www.blaicher.com/2012/06/howto-fixing-a-broken-edid-eeprom-with-a-bus-pirate-v4/
>> [3] https://marc.info/?l=linux-kernel=112838038415265=4

Thanks,
-- 
Ezequiel García, VanguardiaSur
www.vanguardiasur.com.ar

[PATCH] drm/i915/hdmi: Fix weak connector detection

2016-04-05 Thread Ezequiel Garcia 
(Adding Jani again, who got dropped for some reason)

On 1 April 2016 at 16:50, Ezequiel Garcia  
wrote:
> On 01 Apr 06:46 PM, Ville Syrjälä wrote:
>> On Fri, Apr 01, 2016 at 12:38:11PM -0300, Ezequiel Garcia wrote:
>> > El abr. 1, 2016 11:47 AM, "Ville Syrjälä" > > linux.intel.com>
>> > escribió:
>> > >
>> > > On Thu, Mar 31, 2016 at 05:55:03PM -0300, Ezequiel Garcia wrote:
>> > > > Currently, our implementation of drm_connector_funcs.detect is
>> > > > based on getting a valid EDID.
>> > > >
>> > > > This requirement makes the driver fail to detect connected
>> > > > connectors in case of EDID corruption, which prevents from falling
>> > > > back to modes provided by builtin or user-provided EDIDs.
>> > >
>> > > So why are you getting corrupted EDIDs?
>> > >
>> >
>> > Does it matter?
>>
>> Yes. We should fix the real cause (if possible) instead of adding
>> more duct tape.
>>
>
> So, there are two things involved in this patch:
>
> 1.
> There are several reasons why EDID can get screwed, this is
> documented at length [1], and it's the motivation for
> CONFIG_DRM_LOAD_EDID_FIRMWARE to exist.
>
> You can find lots of reports on the internet of people getting
> corrupt EDID from their monitors. For instance, here's one [2].
>
> And even if no firmware is provided using CONFIG_DRM_LOAD_EDID_FIRMWARE,
> the DRM core will provide a 1024x768 fallback mode:
>
> int drm_helper_probe_single_connector_modes(struct drm_connector *connector,
> uint32_t maxX, uint32_t maxY)
> {
> [..]
> if (count == 0 && connector->status == connector_status_connected)
> count = drm_add_modes_noedid(connector, 1024, 768);
>
> But, this only works if the connector is detected.
>
> Since I'm interested in backporting this patch to apply it on the kernels
> I maintain (which are currently deployed on hundreds of machines), I tried
> to find a simple solution. Hence, this patch.
>
> There's no issue to fix here, because broken hardware is a fact of life,
> and not something we can fix or ignore [3].
>
> 2.
> On the other side, the i915 implementation looks suspicious. IMHO,
> drm_connector_funcs.detect should not try to read a valid EDID,
> and just try to detect if the connector is connected or disconnected.
>
> The EDID can be read in drm_connector_helper_funcs.get_modes, as other
> drm/connector drivers are doing (tda998x, tfp410, tegra).
>
> However, I think it's safer to get a simple fix now, and do this
> as follow-up patches.
>
> How does it sound?
>
> [1] Documentation/EDID/HOWTO.txt
> [2] 
> http://www.blaicher.com/2012/06/howto-fixing-a-broken-edid-eeprom-with-a-bus-pirate-v4/
> [3] https://marc.info/?l=linux-kernel=112838038415265=4
> --
> Ezequiel Garcia, VanguardiaSur
> www.vanguardiasur.com.ar



-- 
Ezequiel García, VanguardiaSur
www.vanguardiasur.com.ar

[PATCH] drm/i915/hdmi: Fix weak connector detection

2016-04-01 Thread Ville Syrjälä 
On Fri, Apr 01, 2016 at 12:38:11PM -0300, Ezequiel Garcia wrote:
> El abr. 1, 2016 11:47 AM, "Ville Syrjälä" 
> escribió:
> >
> > On Thu, Mar 31, 2016 at 05:55:03PM -0300, Ezequiel Garcia wrote:
> > > Currently, our implementation of drm_connector_funcs.detect is
> > > based on getting a valid EDID.
> > >
> > > This requirement makes the driver fail to detect connected
> > > connectors in case of EDID corruption, which prevents from falling
> > > back to modes provided by builtin or user-provided EDIDs.
> >
> > So why are you getting corrupted EDIDs?
> >
> 
> Does it matter?

Yes. We should fix the real cause (if possible) instead of adding
more duct tape.

> 
> > >
> > > Let's fix this by improving the detection, with a DDC probe,
> > > if the current EDID-based detection failed.
> > >
> > > Note that a better way of dealing with this could calling
> > > drm_probe_ddc in drm_connector_funcs.detect, and do the
> > > EDID full reading and parsing in drm_connector_helper_funcs.get_modes,
> > > when it's actually needed.
> > >
> > > However, this would be more invasive and thus more error-prone.
> > > The current commit is an attempt to get some uninvasive fix,
> > > and allow for easier backporting.
> > >
> > > Signed-off-by: Ezequiel Garcia 
> > > ---
> > >  drivers/gpu/drm/i915/intel_hdmi.c | 14 ++
> > >  1 file changed, 14 insertions(+)
> > >
> > > diff --git a/drivers/gpu/drm/i915/intel_hdmi.c
> b/drivers/gpu/drm/i915/intel_hdmi.c
> > > index a0d8daed2470..c079206e6681 100644
> > > --- a/drivers/gpu/drm/i915/intel_hdmi.c
> > > +++ b/drivers/gpu/drm/i915/intel_hdmi.c
> > > @@ -1428,6 +1428,20 @@ intel_hdmi_detect(struct drm_connector
> *connector, bool force)
> > >   } else
> > >   status = connector_status_disconnected;
> > >
> > > + /*
> > > +  * The above call to intel_hdmi_set_edid() checked for a valid
> EDID.
> > > +  * However, the EDID can get corrupted for several reasons,
> resulting
> > > +  * in a disconnected status despite the connector being connected.
> > > +  * Hence, let's try one more time, by only probing the DDC.
> > > +  *
> > > +  * This allows the DRM core to fallback to builtin or
> user-provided
> > > +  * EDID firmware, e.g. in drm_helper_probe_single_connector_modes.
> > > +  */
> > > + if (status == connector_status_disconnected)
> > > + if (drm_probe_ddc(intel_gmbus_get_adapter(dev_priv,
> > > + intel_hdmi->ddc_bus)))
> > > + status = connector_status_connected;
> > > +
> > >   intel_display_power_put(dev_priv, POWER_DOMAIN_GMBUS);
> > >
> > >   return status;
> > > --
> > > 2.7.0
> > >
> > > ___
> > > dri-devel mailing list
> > > dri-devel at lists.freedesktop.org
> > > https://lists.freedesktop.org/mailman/listinfo/dri-devel
> >
> > --
> > Ville Syrjälä
> > Intel OTC

-- 
Ville Syrjälä
Intel OTC

[PATCH] drm/i915/hdmi: Fix weak connector detection

2016-04-01 Thread Ville Syrjälä 
On Thu, Mar 31, 2016 at 05:55:03PM -0300, Ezequiel Garcia wrote:
> Currently, our implementation of drm_connector_funcs.detect is
> based on getting a valid EDID.
> 
> This requirement makes the driver fail to detect connected
> connectors in case of EDID corruption, which prevents from falling
> back to modes provided by builtin or user-provided EDIDs.

So why are you getting corrupted EDIDs?

> 
> Let's fix this by improving the detection, with a DDC probe,
> if the current EDID-based detection failed.
> 
> Note that a better way of dealing with this could calling
> drm_probe_ddc in drm_connector_funcs.detect, and do the
> EDID full reading and parsing in drm_connector_helper_funcs.get_modes,
> when it's actually needed.
> 
> However, this would be more invasive and thus more error-prone.
> The current commit is an attempt to get some uninvasive fix,
> and allow for easier backporting.
> 
> Signed-off-by: Ezequiel Garcia 
> ---
>  drivers/gpu/drm/i915/intel_hdmi.c | 14 ++
>  1 file changed, 14 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/intel_hdmi.c 
> b/drivers/gpu/drm/i915/intel_hdmi.c
> index a0d8daed2470..c079206e6681 100644
> --- a/drivers/gpu/drm/i915/intel_hdmi.c
> +++ b/drivers/gpu/drm/i915/intel_hdmi.c
> @@ -1428,6 +1428,20 @@ intel_hdmi_detect(struct drm_connector *connector, 
> bool force)
>   } else
>   status = connector_status_disconnected;
>  
> + /*
> +  * The above call to intel_hdmi_set_edid() checked for a valid EDID.
> +  * However, the EDID can get corrupted for several reasons, resulting
> +  * in a disconnected status despite the connector being connected.
> +  * Hence, let's try one more time, by only probing the DDC.
> +  *
> +  * This allows the DRM core to fallback to builtin or user-provided
> +  * EDID firmware, e.g. in drm_helper_probe_single_connector_modes.
> +  */
> + if (status == connector_status_disconnected)
> + if (drm_probe_ddc(intel_gmbus_get_adapter(dev_priv,
> + intel_hdmi->ddc_bus)))
> + status = connector_status_connected;
> +
>   intel_display_power_put(dev_priv, POWER_DOMAIN_GMBUS);
>  
>   return status;
> -- 
> 2.7.0
> 
> ___
> dri-devel mailing list
> dri-devel at lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/dri-devel

-- 
Ville Syrjälä
Intel OTC

[PATCH] drm/i915/hdmi: Fix weak connector detection

2016-04-01 Thread Ezequiel Garcia 
On 01 Apr 06:46 PM, Ville Syrjälä wrote:
> On Fri, Apr 01, 2016 at 12:38:11PM -0300, Ezequiel Garcia wrote:
> > El abr. 1, 2016 11:47 AM, "Ville Syrjälä"  > linux.intel.com>
> > escribió:
> > >
> > > On Thu, Mar 31, 2016 at 05:55:03PM -0300, Ezequiel Garcia wrote:
> > > > Currently, our implementation of drm_connector_funcs.detect is
> > > > based on getting a valid EDID.
> > > >
> > > > This requirement makes the driver fail to detect connected
> > > > connectors in case of EDID corruption, which prevents from falling
> > > > back to modes provided by builtin or user-provided EDIDs.
> > >
> > > So why are you getting corrupted EDIDs?
> > >
> > 
> > Does it matter?
> 
> Yes. We should fix the real cause (if possible) instead of adding
> more duct tape.
> 

So, there are two things involved in this patch:

1.
There are several reasons why EDID can get screwed, this is
documented at length [1], and it's the motivation for
CONFIG_DRM_LOAD_EDID_FIRMWARE to exist.

You can find lots of reports on the internet of people getting
corrupt EDID from their monitors. For instance, here's one [2].

And even if no firmware is provided using CONFIG_DRM_LOAD_EDID_FIRMWARE,
the DRM core will provide a 1024x768 fallback mode:

int drm_helper_probe_single_connector_modes(struct drm_connector *connector,
uint32_t maxX, uint32_t maxY)
{
[..]
if (count == 0 && connector->status == connector_status_connected)
count = drm_add_modes_noedid(connector, 1024, 768);

But, this only works if the connector is detected.

Since I'm interested in backporting this patch to apply it on the kernels
I maintain (which are currently deployed on hundreds of machines), I tried
to find a simple solution. Hence, this patch.

There's no issue to fix here, because broken hardware is a fact of life,
and not something we can fix or ignore [3].

2.
On the other side, the i915 implementation looks suspicious. IMHO,
drm_connector_funcs.detect should not try to read a valid EDID,
and just try to detect if the connector is connected or disconnected.

The EDID can be read in drm_connector_helper_funcs.get_modes, as other
drm/connector drivers are doing (tda998x, tfp410, tegra).

However, I think it's safer to get a simple fix now, and do this
as follow-up patches.

How does it sound?

[1] Documentation/EDID/HOWTO.txt
[2] 
http://www.blaicher.com/2012/06/howto-fixing-a-broken-edid-eeprom-with-a-bus-pirate-v4/
[3] https://marc.info/?l=linux-kernel=112838038415265=4
-- 
Ezequiel Garcia, VanguardiaSur
www.vanguardiasur.com.ar

[PATCH] drm/i915/hdmi: Fix weak connector detection

2016-04-01 Thread Ezequiel Garcia 
El abr. 1, 2016 11:47 AM, "Ville Syrjälä" 
escribió:
>
> On Thu, Mar 31, 2016 at 05:55:03PM -0300, Ezequiel Garcia wrote:
> > Currently, our implementation of drm_connector_funcs.detect is
> > based on getting a valid EDID.
> >
> > This requirement makes the driver fail to detect connected
> > connectors in case of EDID corruption, which prevents from falling
> > back to modes provided by builtin or user-provided EDIDs.
>
> So why are you getting corrupted EDIDs?
>

Does it matter?

> >
> > Let's fix this by improving the detection, with a DDC probe,
> > if the current EDID-based detection failed.
> >
> > Note that a better way of dealing with this could calling
> > drm_probe_ddc in drm_connector_funcs.detect, and do the
> > EDID full reading and parsing in drm_connector_helper_funcs.get_modes,
> > when it's actually needed.
> >
> > However, this would be more invasive and thus more error-prone.
> > The current commit is an attempt to get some uninvasive fix,
> > and allow for easier backporting.
> >
> > Signed-off-by: Ezequiel Garcia 
> > ---
> >  drivers/gpu/drm/i915/intel_hdmi.c | 14 ++
> >  1 file changed, 14 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/i915/intel_hdmi.c
b/drivers/gpu/drm/i915/intel_hdmi.c
> > index a0d8daed2470..c079206e6681 100644
> > --- a/drivers/gpu/drm/i915/intel_hdmi.c
> > +++ b/drivers/gpu/drm/i915/intel_hdmi.c
> > @@ -1428,6 +1428,20 @@ intel_hdmi_detect(struct drm_connector
*connector, bool force)
> >   } else
> >   status = connector_status_disconnected;
> >
> > + /*
> > +  * The above call to intel_hdmi_set_edid() checked for a valid
EDID.
> > +  * However, the EDID can get corrupted for several reasons,
resulting
> > +  * in a disconnected status despite the connector being connected.
> > +  * Hence, let's try one more time, by only probing the DDC.
> > +  *
> > +  * This allows the DRM core to fallback to builtin or
user-provided
> > +  * EDID firmware, e.g. in drm_helper_probe_single_connector_modes.
> > +  */
> > + if (status == connector_status_disconnected)
> > + if (drm_probe_ddc(intel_gmbus_get_adapter(dev_priv,
> > + intel_hdmi->ddc_bus)))
> > + status = connector_status_connected;
> > +
> >   intel_display_power_put(dev_priv, POWER_DOMAIN_GMBUS);
> >
> >   return status;
> > --
> > 2.7.0
> >
> > ___
> > dri-devel mailing list
> > dri-devel at lists.freedesktop.org
> > https://lists.freedesktop.org/mailman/listinfo/dri-devel
>
> --
> Ville Syrjälä
> Intel OTC
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[PATCH] drm/i915/hdmi: Fix weak connector detection

2016-03-31 Thread Ezequiel Garcia 
Currently, our implementation of drm_connector_funcs.detect is
based on getting a valid EDID.

This requirement makes the driver fail to detect connected
connectors in case of EDID corruption, which prevents from falling
back to modes provided by builtin or user-provided EDIDs.

Let's fix this by improving the detection, with a DDC probe,
if the current EDID-based detection failed.

Note that a better way of dealing with this could calling
drm_probe_ddc in drm_connector_funcs.detect, and do the
EDID full reading and parsing in drm_connector_helper_funcs.get_modes,
when it's actually needed.

However, this would be more invasive and thus more error-prone.
The current commit is an attempt to get some uninvasive fix,
and allow for easier backporting.

Signed-off-by: Ezequiel Garcia 
---
 drivers/gpu/drm/i915/intel_hdmi.c | 14 ++
 1 file changed, 14 insertions(+)

diff --git a/drivers/gpu/drm/i915/intel_hdmi.c 
b/drivers/gpu/drm/i915/intel_hdmi.c
index a0d8daed2470..c079206e6681 100644
--- a/drivers/gpu/drm/i915/intel_hdmi.c
+++ b/drivers/gpu/drm/i915/intel_hdmi.c
@@ -1428,6 +1428,20 @@ intel_hdmi_detect(struct drm_connector *connector, bool 
force)
} else
status = connector_status_disconnected;

+   /*
+* The above call to intel_hdmi_set_edid() checked for a valid EDID.
+* However, the EDID can get corrupted for several reasons, resulting
+* in a disconnected status despite the connector being connected.
+* Hence, let's try one more time, by only probing the DDC.
+*
+* This allows the DRM core to fallback to builtin or user-provided
+* EDID firmware, e.g. in drm_helper_probe_single_connector_modes.
+*/
+   if (status == connector_status_disconnected)
+   if (drm_probe_ddc(intel_gmbus_get_adapter(dev_priv,
+   intel_hdmi->ddc_bus)))
+   status = connector_status_connected;
+
intel_display_power_put(dev_priv, POWER_DOMAIN_GMBUS);

return status;
-- 
2.7.0