[PATCH 0/3] i2c: davinci: Fix problems discovered on Keystone CPU

[PATCH 0/3] i2c: davinci: Fix problems discovered on Keystone CPU

[Alexander Sverdlin]

During intensive I2C tests on Keystone CPU we've discovered several problems
with the i2c-davinci driver. Maybe Keystone is the first relatively powerful CPU
utilizing davinci controller and therefore the races in the driver became more
obvious, but it's clear that many users had problems with the driver and even
though driver has received many band aids over the years, nobody addressed the
original racy design.

The series address the follwing problems:
"i2c: davinci: Rework racy ISR" -- stop the parallel activities in the driver
including concurrect registers access. Also simplifies the design and removes
some bad aids.
"i2c: davinci: Refactor i2c_davinci_wait_bus_not_busy()" -- the routine is
over-designed and instead of "waiting" will trigger the bus recovering
immediately.
"i2c: davinci: Avoid sending to own address" -- works around one davinci
controller issue when it unexpectedly switches to some sort of slave mode
trying to send to its own address. The controller remains in this locked state
until reset, so it's better to avoid this situation than to deal with transfer
timeouts.

Re: [PATCH 0/3] i2c: davinci: Fix problems discovered on Keystone CPU

[Grygorii.Strashko-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org]

On 03/11/2015 03:08 PM, Alexander Sverdlin wrote:
> During intensive I2C tests on Keystone CPU we've discovered several problems
> with the i2c-davinci driver. Maybe Keystone is the first relatively powerful CPU
> utilizing davinci controller and therefore the races in the driver became more
> obvious, but it's clear that many users had problems with the driver and even
> though driver has received many band aids over the years, nobody addressed the
> original racy design.
> 
> The series address the follwing problems:
> "i2c: davinci: Rework racy ISR" -- stop the parallel activities in the driver
> including concurrect registers access. Also simplifies the design and removes
> some bad aids.
> "i2c: davinci: Refactor i2c_davinci_wait_bus_not_busy()" -- the routine is
> over-designed and instead of "waiting" will trigger the bus recovering
> immediately.
> "i2c: davinci: Avoid sending to own address" -- works around one davinci
> controller issue when it unexpectedly switches to some sort of slave mode
> trying to send to its own address. The controller remains in this locked state
> until reset, so it's better to avoid this situation than to deal with transfer
> timeouts.
> 


Have you used git format-patch --cover-letter?
Overall stats and list of patches are missing.

Also I think It'll be better to send patches 2/3 first, as
they have more chances to be merged. 

regards,
-grygorii

Re: [PATCH 0/3] i2c: davinci: Fix problems discovered on Keystone CPU

[Alexander Sverdlin]

Hi!

On 11/03/15 19:35, ext Grygorii.Strashko-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org wrote:
>> The series address the follwing problems:
>> > "i2c: davinci: Rework racy ISR" -- stop the parallel activities in the driver
>> > including concurrect registers access. Also simplifies the design and removes
>> > some bad aids.
>> > "i2c: davinci: Refactor i2c_davinci_wait_bus_not_busy()" -- the routine is
>> > over-designed and instead of "waiting" will trigger the bus recovering
>> > immediately.
>> > "i2c: davinci: Avoid sending to own address" -- works around one davinci
>> > controller issue when it unexpectedly switches to some sort of slave mode
>> > trying to send to its own address. The controller remains in this locked state
>> > until reset, so it's better to avoid this situation than to deal with transfer
>> > timeouts.
>> > 
> 
> Have you used git format-patch --cover-letter?
> Overall stats and list of patches are missing.

Will do in v2...

> Also I think It'll be better to send patches 2/3 first, as
> they have more chances to be merged. 

First patch is an important fix for blocking problem and therefore a candidate for
-stable backports. So, it should be less dependent of the less-important 2 and 3.

-- 
Best regards,
Alexander Sverdlin.

Re: [PATCH 0/3] i2c: davinci: Fix problems discovered on Keystone CPU

[Wolfram Sang]

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On Thu, Mar 12, 2015 at 08:52:39AM +0100, Alexander Sverdlin wrote:
> Hi!
> 
> On 11/03/15 19:35, ext Grygorii.Strashko-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org wrote:
> >> The series address the follwing problems:
> >> > "i2c: davinci: Rework racy ISR" -- stop the parallel activities in the driver
> >> > including concurrect registers access. Also simplifies the design and removes
> >> > some bad aids.
> >> > "i2c: davinci: Refactor i2c_davinci_wait_bus_not_busy()" -- the routine is
> >> > over-designed and instead of "waiting" will trigger the bus recovering
> >> > immediately.
> >> > "i2c: davinci: Avoid sending to own address" -- works around one davinci
> >> > controller issue when it unexpectedly switches to some sort of slave mode
> >> > trying to send to its own address. The controller remains in this locked state
> >> > until reset, so it's better to avoid this situation than to deal with transfer
> >> > timeouts.
> >> > 
> > 
> > Have you used git format-patch --cover-letter?
> > Overall stats and list of patches are missing.
> 
> Will do in v2...

And please make sure the patches are chained to the cover-letter. That
makes reviewing much easier.

> First patch is an important fix for blocking problem and therefore a candidate for
> -stable backports. So, it should be less dependent of the less-important 2 and 3.

IMO this patch is too intrusive for stable, so I won't add the tag. You
may request that individually to stable maintainers, though, if you
disagree.


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