* PXA PWM possible regression after 3.5: backlight remains off after resume
@ 2012-09-23 15:20 Paul Parsons
2012-09-23 17:22 ` Thierry Reding
0 siblings, 1 reply; 5+ messages in thread
From: Paul Parsons @ 2012-09-23 15:20 UTC (permalink / raw)
To: linux-arm-kernel
There is a possible PXA PWM regression between 3.5 and 3.6-rc6: if I
suspend and then resume an iPAQ hx4700, the backlight remains off.
In 3.5 the backlight would turn on after the resume.
I presumed this is a PWM issue because the PXA PWM driver was reworked
and moved trees between 3.5 and 3.6-rc6. And there was mention of
broken PWM drivers about a month ago, for example:
http://lists.infradead.org/pipermail/linux-arm-kernel/2012-August/115717.html
Does my backlight breakage sound familiar to anybody? Is there
anything obvious I can try before debugging it further?
Regards,
Paul
^ permalink raw reply [flat|nested] 5+ messages in thread
* PXA PWM possible regression after 3.5: backlight remains off after resume
2012-09-23 15:20 PXA PWM possible regression after 3.5: backlight remains off after resume Paul Parsons
@ 2012-09-23 17:22 ` Thierry Reding
2012-09-23 18:13 ` Paul Parsons
0 siblings, 1 reply; 5+ messages in thread
From: Thierry Reding @ 2012-09-23 17:22 UTC (permalink / raw)
To: linux-arm-kernel
On Sun, Sep 23, 2012 at 04:20:24PM +0100, Paul Parsons wrote:
> There is a possible PXA PWM regression between 3.5 and 3.6-rc6: if I
> suspend and then resume an iPAQ hx4700, the backlight remains off.
>
> In 3.5 the backlight would turn on after the resume.
>
> I presumed this is a PWM issue because the PXA PWM driver was reworked
> and moved trees between 3.5 and 3.6-rc6. And there was mention of
> broken PWM drivers about a month ago, for example:
> http://lists.infradead.org/pipermail/linux-arm-kernel/2012-August/115717.html
>
> Does my backlight breakage sound familiar to anybody? Is there
> anything obvious I can try before debugging it further?
Looking at the code from before the move to the PWM subsystem I have a
hard time understanding how this could have worked for supend/resume in
the first place. The driver has never supported the supend and resume
callbacks. Maybe it is also a problem related to some other change.
Clocking would be a likely candidate. But again I wonder how this ever
worked properly without the suspend and resume callbacks.
Can you pinpoint more exactly when this failed to break. PXA PWM was
already included in 3.6-rc1 so if it is related then it should have
happened at that time already.
Thierry
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^ permalink raw reply [flat|nested] 5+ messages in thread
* PXA PWM possible regression after 3.5: backlight remains off after resume
2012-09-23 17:22 ` Thierry Reding
@ 2012-09-23 18:13 ` Paul Parsons
2012-09-25 19:43 ` Robert Jarzmik
0 siblings, 1 reply; 5+ messages in thread
From: Paul Parsons @ 2012-09-23 18:13 UTC (permalink / raw)
To: linux-arm-kernel
Hello Thierry,
On 23/09/12 18:22, Thierry Reding wrote:
> On Sun, Sep 23, 2012 at 04:20:24PM +0100, Paul Parsons wrote:
>> There is a possible PXA PWM regression between 3.5 and 3.6-rc6: if I
>> suspend and then resume an iPAQ hx4700, the backlight remains off.
>>
>> In 3.5 the backlight would turn on after the resume.
>>
>> I presumed this is a PWM issue because the PXA PWM driver was reworked
>> and moved trees between 3.5 and 3.6-rc6. And there was mention of
>> broken PWM drivers about a month ago, for example:
>> http://lists.infradead.org/pipermail/linux-arm-kernel/2012-August/115717.html
>>
>> Does my backlight breakage sound familiar to anybody? Is there
>> anything obvious I can try before debugging it further?
>
> Looking at the code from before the move to the PWM subsystem I have a
> hard time understanding how this could have worked for supend/resume in
> the first place. The driver has never supported the supend and resume
> callbacks. Maybe it is also a problem related to some other change.
> Clocking would be a likely candidate. But again I wonder how this ever
> worked properly without the suspend and resume callbacks.
>
> Can you pinpoint more exactly when this failed to break. PXA PWM was
> already included in 3.6-rc1 so if it is related then it should have
> happened at that time already.
The same failure is also present in 3.6-rc1.
Just to be clear, are you saying that drivers/pwm/pwm-pxa.c should
include suspend/resume handlers like in drivers/pwm/pwm-samsung.c ?
Agreed that it is possible that recent changes exposed a latent bug
somewhere, and that turning the backlight on after resume should never
have worked.
^ permalink raw reply [flat|nested] 5+ messages in thread
* PXA PWM possible regression after 3.5: backlight remains off after resume
2012-09-23 18:13 ` Paul Parsons
@ 2012-09-25 19:43 ` Robert Jarzmik
2012-09-26 2:02 ` Paul Parsons
0 siblings, 1 reply; 5+ messages in thread
From: Robert Jarzmik @ 2012-09-25 19:43 UTC (permalink / raw)
To: linux-arm-kernel
Paul Parsons <lost.distance@yahoo.com> writes:
> The same failure is also present in 3.6-rc1.
>
> Just to be clear, are you saying that drivers/pwm/pwm-pxa.c should
> include suspend/resume handlers like in drivers/pwm/pwm-samsung.c ?
>
> Agreed that it is possible that recent changes exposed a latent bug
> somewhere, and that turning the backlight on after resume should never
> have worked.
Hi Paul,
I checked on the mioa701 board (see [1]).
On my board, the backlight if fully driven by PXA PWM0, and the suspend/resume
is working perfectly.
So I don't thing anything is needed for suspend/resume wrt PWM (empirically).
Cheers.
--
Robert
[1]
$ cat /sys/class/backlight/pwm-backlight/actual_brightness
50
$ cat /sys/class/backlight/pwm-backlight/actual_brightness
50
$ echo 90 > /sys/class/backlight/pwm-backlight/brightness
$ echo mem > /sys/power/state
$
$ cat /sys/class/backlight/pwm-backlight/actual_brightness
90
$ uname -a
Linux mioa701 3.6.0-rc6+ #26 PREEMPT Sat Sep 22 22:08:41 CEST 2012 armv5tel unknown
^ permalink raw reply [flat|nested] 5+ messages in thread
* PXA PWM possible regression after 3.5: backlight remains off after resume
2012-09-25 19:43 ` Robert Jarzmik
@ 2012-09-26 2:02 ` Paul Parsons
0 siblings, 0 replies; 5+ messages in thread
From: Paul Parsons @ 2012-09-26 2:02 UTC (permalink / raw)
To: linux-arm-kernel
On 25/09/12 20:43, Robert Jarzmik wrote:
> Paul Parsons <lost.distance@yahoo.com> writes:
>
>> The same failure is also present in 3.6-rc1.
>>
>> Just to be clear, are you saying that drivers/pwm/pwm-pxa.c should
>> include suspend/resume handlers like in drivers/pwm/pwm-samsung.c ?
>>
>> Agreed that it is possible that recent changes exposed a latent bug
>> somewhere, and that turning the backlight on after resume should never
>> have worked.
>
> Hi Paul,
>
> I checked on the mioa701 board (see [1]).
> On my board, the backlight if fully driven by PXA PWM0, and the suspend/resume
> is working perfectly.
>
> So I don't thing anything is needed for suspend/resume wrt PWM (empirically).
You're right. I belatedly reached the same conclusion after I noticed
that only the pwm-samsung driver included any suspend/resume handlers:
the other drivers can't all be broken!
Fortunately I have just identified the problem: the PXA27X PWM device
numbering scheme has changed, breaking the hx4700 platform and probably
other PXA27X platforms which use PWM1 or PWM2.
Regards,
Paul
^ permalink raw reply [flat|nested] 5+ messages in thread
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2012-09-23 15:20 PXA PWM possible regression after 3.5: backlight remains off after resume Paul Parsons
2012-09-23 17:22 ` Thierry Reding
2012-09-23 18:13 ` Paul Parsons
2012-09-25 19:43 ` Robert Jarzmik
2012-09-26 2:02 ` Paul Parsons
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