Re: [PATCH 0/3] Add OMAP hardware spinlock misc driver

2010-10-20 Thread Daniel Walker
On Wed, 2010-10-20 at 10:53 +0100, Russell King - ARM Linux wrote:
> 
> To: Ohad Ben-Cohen 
> Cc: Hari Kanigeri , Benoit Cousson ,
> Tony Lindgren , Greg KH ,
> linux-ker...@vger.kernel.org,
> Grant Likely , ma...@codeaurora.org,
> a...@linux-foundation.org, Suman Anna ,
> ma...@codeaurora.orgmattw, linux-arm-ker...@lists.infradead.org
> 
> which includes an invalid address "ma...@codeaurora.orgmattw".  Is there
> a reason why you're excluding the linux-omap list from your message and
> subsequent discussion?

I was trying to add Matt to the CC, but I guess I accidentally deleted
some CC's .. So it was purely an accident.

Daniel

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Re: [PATCH] ARM: Fix HWCAP_TLS flag for ARM11MPCore/Cortex-A9

2010-10-06 Thread Daniel Walker
On Wed, 2010-10-06 at 17:00 -0700, Tony Lindgren wrote:

> - .long   HWCAP_SWP|HWCAP_HALF|HWCAP_THUMB|HWCAP_FAST_MULT|HWCAP_EDSP
> + .long   
> HWCAP_SWP|HWCAP_HALF|HWCAP_THUMB|HWCAP_FAST_MULT|HWCAP_EDSP|HWCAP_TLS


Thanks for catching this.. I have no idea how this happened, I must have
somehow been using a pre July 5th kernel when I made the patch.. Maybe a
forgotten bisect or something.

Daniel

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Re: [RFC 3/3] mm: iommu: The Virtual Contiguous Memory Manager

2010-07-01 Thread Daniel Walker
On Thu, 2010-07-01 at 15:00 -0700, Zach Pfeffer wrote:


> Additionally, the current IOMMU interface does not allow users to
> associate one page table with multiple IOMMUs unless the user explicitly
> wrote a muxed device underneith the IOMMU interface. This also could be
> done, but would have to be done for every such use case. Since the
> particular topology is run-time configurable all of these use-cases and
> more can be expressed without pushing the topology into the low-level
> IOMMU driver.
> 
> The VCMM takes the long view. Its designed for a future in which the
> number of IOMMUs will go up and the ways in which these IOMMUs are
> composed will vary from system to system, and may vary at
> runtime. Already, there are ~20 different IOMMU map implementations in
> the kernel. Had the Linux kernel had the VCMM, many of those
> implementations could have leveraged the mapping and topology management
> of a VCMM, while focusing on a few key hardware specific functions (map
> this physical address, program the page table base register).

So if we include this code which "map implementations" could you
collapse into this implementations ? Generally , what currently existing
code can VCMM help to eliminate?

Daniel

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Re: [RFC 3/3] mm: iommu: The Virtual Contiguous Memory Manager

2010-07-01 Thread Daniel Walker
On Thu, 2010-07-01 at 21:38 +0200, Andi Kleen wrote:
> > 
> > > Also for me it's still quite unclear why we would want this code at all...
> > > It doesn't seem to do anything you couldn't do with the existing 
> > > interfaces.
> > 
> > I don't know all that much about what Zach's done here, but from what
> > he's said so far it looks like this help to manage lots of IOMMUs on a
> > single system.. On x86 it seems like there's not all that many IOMMUs in
> > comparison .. Zach mentioned 10 to 100 IOMMUs ..
> 
> The current code can manage multiple IOMMUs fine.

He demonstrated the usage of his code in one of the emails he sent out
initially. Did you go over that, and what (or how many) step would you
use with the current code to do the same thing?

Daniel

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Re: [RFC 3/3] mm: iommu: The Virtual Contiguous Memory Manager

2010-07-01 Thread Daniel Walker
On Thu, 2010-07-01 at 20:02 +0200, Andi Kleen wrote:
> > What license (name/type) is this?
> 
> IANAL, but AFAIK standard wisdom is that "disclaimer in the documentation
> and/or other materials provided" is generally not acceptable for Linux
> because it's an excessive burden for all distributors.

It's the BSD license ..

> Also for me it's still quite unclear why we would want this code at all...
> It doesn't seem to do anything you couldn't do with the existing interfaces.

I don't know all that much about what Zach's done here, but from what
he's said so far it looks like this help to manage lots of IOMMUs on a
single system.. On x86 it seems like there's not all that many IOMMUs in
comparison .. Zach mentioned 10 to 100 IOMMUs ..

Daniel

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Re: [linux-pm] [PATCH 0/8] Suspend block api (version 6)

2010-05-17 Thread Daniel Walker
On Mon, 2010-05-17 at 13:04 -0400, James Bottomley wrote:

> I'm not sure this is real world, either.  Developers can fire up
> powertop from the command line when their phone isn't idling for as long
> as it should.  But a phone is a consumer device: the average smart phone
> user just wants to browse the web, get email, go to facebook and play
> with some cool apps.  If one of those cool apps is rogue, they're not
> really going to know which one or how to find it (and firing up powertop
> from the command line isn't something which will occur to them as a
> matter of routine).
> 
> One of the nice things that suspend blockers actually does is to give
> the kernel a clear name for the process blocking suspend (and thus
> consuming power).  This allows a nice way to assign power budget to the
> application and present who's using what in a nice visible form, which
> does facilitate the reporting of bad apps, even for the non-developer
> user.

If you have an idle based PM system you could get the same information
from having scheduler statistics. Since the "bad" apps are the ones that
are always either running or ready to run, and they would hardly ever
sleep. I don't know if there are specific scheduler statistics for that,
but it doesn't seem like it would be hard to make. It's even much more
natural than getting statistics from suspend blockers, since it requires
the app to be custom made to use suspend blockers.

Daniel

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Re: [linux-pm] [PATCH 0/8] Suspend block api (version 6)

2010-05-14 Thread Daniel Walker
On Thu, 2010-05-13 at 14:46 -0700, Greg KH wrote:
> On Thu, May 13, 2010 at 02:33:29PM -0700, Daniel Walker wrote:
> > On Thu, 2010-05-13 at 23:27 +0200, Rafael J. Wysocki wrote:
> > 
> > > Because someone would have to remove suspend blockers (or rather 
> > > wakelocks)
> > > from the drivers, test that they work correctly without suspend blockers 
> > > and
> > > submit the modified versions.  Going forward, every party responsible for 
> > > such
> > > a driver would have to maintain an out-of-tree version with suspend 
> > > blockers
> > > (or wakelocks) anyway, so the incentive to do that is zero.
> > 
> > They should work without wakelock since wakelock are optional .. I mean
> > there's nothing in suspend blockers I've seen that indicates it's
> > required for some drivers to work. So it's just a matter of patching out
> > the wakelocks, with no need to re-test anything.
> > 
> > You get the driver mainlined, then maintain a small patch to add
> > wakelocks. Not hard at all , with lots of incentive to do so since you
> > don't have to maintain such a large block of code out of tree.
> 
> Sorry, but it doesn't seem to work that way.  Look at the large number
> of out-of-tree android device drivers that remain sitting there because
> of the lack of this interface being in the kernel.

I don't think that's due to this interface tho. During your CELF
presentation you noted several bits of code that could go in right now
but haven't (and still haven't as far as I've seen). I'm actively
pushing code related to Android (with wakelocks removed).. Putting a
wakelock contingency on everything to me doesn't make much sense.

> Also note that such a driver, without wakelocks, would never get tested,
> and so, things start quickly diverging.

That's not totally true. For example the MMC driver had wakelocks (I
think, or for sure mmc core does), and the MMC driver has been tested
for G1 and works fine so far without them. I have code that is queued
for my tree that will enable MMC on G1. I can merge Nexus one support
through my tree also which would allow all the drivers for that device
to eventually be used.

With that device support in mainline then those drivers become nice
things to have with or with out wakelocks. You don't need wakelocks to
run Debian or anything else except Android.

Daniel

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Re: [linux-pm] [PATCH 0/8] Suspend block api (version 6)

2010-05-13 Thread Daniel Walker
On Thu, 2010-05-13 at 23:27 +0200, Rafael J. Wysocki wrote:

> Because someone would have to remove suspend blockers (or rather wakelocks)
> from the drivers, test that they work correctly without suspend blockers and
> submit the modified versions.  Going forward, every party responsible for such
> a driver would have to maintain an out-of-tree version with suspend blockers
> (or wakelocks) anyway, so the incentive to do that is zero.

They should work without wakelock since wakelock are optional .. I mean
there's nothing in suspend blockers I've seen that indicates it's
required for some drivers to work. So it's just a matter of patching out
the wakelocks, with no need to re-test anything.

You get the driver mainlined, then maintain a small patch to add
wakelocks. Not hard at all , with lots of incentive to do so since you
don't have to maintain such a large block of code out of tree.

> Practically, as long as the opportunistic suspend is out of tree, there will 
> be
> a _growing_ number of out-of-tree drivers out there, which is not acceptable
> in the long run.

I don't see why your saying that. These driver should work with out all
of this, which means they can get mainlined right now.

Daniel

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Re: [linux-pm] [PATCH 0/8] Suspend block api (version 6)

2010-05-13 Thread Daniel Walker
On Thu, 2010-05-13 at 23:11 +0200, Rafael J. Wysocki wrote:
> On Thursday 13 May 2010, Matthew Garrett wrote:
> > On Thu, May 13, 2010 at 12:36:34PM -0700, Daniel Walker wrote:
> > > On Thu, 2010-05-13 at 20:11 +0100, Matthew Garrett wrote:
> > > > See feature-removal-schedule.txt. So far we have no indication that 
> > > > it's 
> > > > going to be replaced, because nobody has actually suggested a working 
> > > > way to do this better. If we had a concrete implementation proposal for 
> > > > that then we'd be in a pretty different position right now.
> > > 
> > > Ok, feature-removal-schedule.txt applies to everything tho. What your
> > > saying is that if this interface only last a short time it might take 6
> > > months, if it last for a long time it would take longer. There's no easy
> > > way to know that Google is the only user after some amount of time
> > > passes.
> > 
> > If the interface is there for a long time, it's because we haven't come 
> > up with anything better. And if we haven't come up with anything better, 
> > the interface deserves to be there.
> 
> Moreover, the interface is already in use out-of-tree and that usage is
> actually _growing_, so we have a growing number of out-of-tree drivers that
> aren't megrgeable for this very reason.

Why can't we merge the drivers? Drivers are just drivers, they don't
need this to get merged. (They need it to work with Android)

Daniel

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Re: [linux-pm] [PATCH 0/8] Suspend block api (version 6)

2010-05-13 Thread Daniel Walker
On Thu, 2010-05-13 at 13:23 -0700, Tony Lindgren wrote:
> * Matthew Garrett  [100513 13:03]:
> > On Thu, May 13, 2010 at 01:00:04PM -0700, Tony Lindgren wrote:
> > 
> > > The system stays running because there's something to do. The system
> > > won't suspend until all the processors hit the kernel idle loop and
> > > the next_timer_interrupt_critical() returns nothing.
> > 
> > At which point an application in a busy loop cripples you.
> 
> Maybe you could deal with the misbehaving untrusted apps in the userspace
> by sending kill -STOP to them when the screen blanks? Then continue
> when some event wakes up the system again.

Couldn't you just use priorities (nice), or cgroups to deal with that?
I'm sure there is a way to limit an apps runtime, so the system does go
idle sometimes.

> > I think we could implement your suggestion more easily by just giving
> > untrusted applications an effectively infinite amount of timer slack,
> > but it still doesn't handle the case where an app behaves excrutiatingly
> > badly.
> 
> Hmm, if you use timer slack then you still need to search through
> the whole timer list instead of a smaller critical timer list.
> Both ways sound doable though.

There are deferrable timers already in Linux.. It seems like it would
just be an extension of that.

Daniel

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Re: [linux-pm] [PATCH 0/8] Suspend block api (version 6)

2010-05-13 Thread Daniel Walker
On Thu, 2010-05-13 at 20:11 +0100, Matthew Garrett wrote:
> On Thu, May 13, 2010 at 11:59:37AM -0700, Daniel Walker wrote:
> > On Thu, 2010-05-13 at 19:36 +0100, Matthew Garrett wrote:
> > > Deprecating sysfs interfaces can be done within 6 months or so, 
> > > especially if there's only one real consumer.
> > 
> > I'll assume your right (can you give an example of this?), but why
> > should we even add it if we know it's already going to get replaced.
> > It's like it's pre-deprecated ..
> 
> See feature-removal-schedule.txt. So far we have no indication that it's 
> going to be replaced, because nobody has actually suggested a working 
> way to do this better. If we had a concrete implementation proposal for 
> that then we'd be in a pretty different position right now.

Ok, feature-removal-schedule.txt applies to everything tho. What your
saying is that if this interface only last a short time it might take 6
months, if it last for a long time it would take longer. There's no easy
way to know that Google is the only user after some amount of time
passes.

Daniel

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Re: [linux-pm] [PATCH 0/8] Suspend block api (version 6)

2010-05-13 Thread Daniel Walker
On Thu, 2010-05-13 at 19:36 +0100, Matthew Garrett wrote:
> On Thu, May 13, 2010 at 11:25:57AM -0700, Daniel Walker wrote:
> 
> > The problem is that once this userspace interface is exposed, it's
> > nearly permanent and has to be support for a long long time .. It might
> > seen trivial to just remove something your not using, but we never know
> > who is using what once the kernel is released.
> 
> Deprecating sysfs interfaces can be done within 6 months or so, 
> especially if there's only one real consumer.

I'll assume your right (can you give an example of this?), but why
should we even add it if we know it's already going to get replaced.
It's like it's pre-deprecated ..

Daniel


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Re: [linux-pm] [PATCH 0/8] Suspend block api (version 6)

2010-05-13 Thread Daniel Walker
On Thu, 2010-05-13 at 11:17 -0700, Brian Swetland wrote:

> 
> I'm not sure this necessitates using only debugfs for the userspace
> interface.  A userspace interface is necessary to accomplish what
> we're trying to do here, otherwise we have only half a solution, and
> our hope is that it'd be a stable interface (as userspace interfaces
> are supposed to be) for as long as its needed.  I could totally
> imagine the userspace interface eventually becoming a no-op or
> punching through to some other facility, depending on how this problem
> is solved long-term in the ideal post-suspend-block future.

The problem is that once this userspace interface is exposed, it's
nearly permanent and has to be support for a long long time .. It might
seen trivial to just remove something your not using, but we never know
who is using what once the kernel is released.

Daniel

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Re: [linux-pm] [PATCH 0/8] Suspend block api (version 6)

2010-05-13 Thread Daniel Walker
On Thu, 2010-05-13 at 13:17 +0100, Matthew Garrett wrote:
> On Wed, May 12, 2010 at 09:35:30PM -0600, Paul Walmsley wrote:
> > 
> > Figuring out a different way to do this should not limit Android at all, 
> > since Google can do what other Linux distributions do and continue to 
> > patch opportunistic suspend/suspend-block calls into their kernels as 
> > needed to ship devices, while contributing towards a different solution to 
> > the problem.
> 
> I basically agree, except that despite having a year to do so none of us 
> have come up with a different way that would actually work. Google have 
> done this work. Who's going to prove that there is actually a different 
> way to do this?

We all feel the pain of inelegance right? I think it's clear that this
system will not last (but there's no other immediate option) .. That
doesn't mean we should reject it, but we need to be clear that this
system will get replaced. So we should format the patches appropriately.
To me the userspace aspect is a permanent change .. If we could drop
that (or put it into debugfs) then it would make this a lot easy to
accept as a stepping stone.

Daniel

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[PATCH] arm: omap: iovmm: add missing mutex_unlock

2009-09-26 Thread Daniel Walker
I was using Coccinelle with the mutex_unlock semantic patch, and it
unconvered this problem. It appears to be a valid missing unlock issue.
This change should correct it by moving the unlock below the label.

This patch is against the mainline kernel.

Cc: Julia Lawall 
Cc: Kevin Hilman 
Cc: Tony Lindgren 
Signed-off-by: Daniel Walker 
---
 arch/arm/plat-omap/iovmm.c |3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/arch/arm/plat-omap/iovmm.c b/arch/arm/plat-omap/iovmm.c
index 57f7122..9b6cb90 100644
--- a/arch/arm/plat-omap/iovmm.c
+++ b/arch/arm/plat-omap/iovmm.c
@@ -363,8 +363,9 @@ void *da_to_va(struct iommu *obj, u32 da)
goto out;
}
va = area->va;
-   mutex_unlock(&obj->mmap_lock);
 out:
+   mutex_unlock(&obj->mmap_lock);
+
return va;
 }
 EXPORT_SYMBOL_GPL(da_to_va);
-- 
1.6.0.4

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