[REGRESSION] gpio: omap: ensure irq is enabled before wakeup

[REGRESSION] gpio: omap: ensure irq is enabled before wakeup

[Eric Schikschneit]

Summary: OMAP patch causes SPI bus transaction failure on TI CPU
Commit: c859e0d479b3b4f6132fc12637c51e01492f31f6
Kernel version: 5.10.87


The detailed description:


I know this is a old commit at this point, but we have observed a regression caused by this commit. It causes improper toggle during a SPI transaction with a microcontroller. The CPU in use is Texas Instruments AM3352BZCZA80. The microcontroller in use is a PIC based micro. I have logic capture images available to show the signal difference that is causing confusion on the SPI bus.


..............................................

Eric Schikschneit

Embedded Linux Engineer

NovaTech, LLC
13555 W. 107th Street
Lenexa, KS 66215
(913) 451-1880 (main)
(913) 742-XXXX (direct)

Eric.Schikschneit@novatechweb.com

Re: [REGRESSION] gpio: omap: ensure irq is enabled before wakeup

[Thorsten Leemhuis]

Hi, this is your Linux kernel regression tracker.

On 01.06.22 17:56, Eric Schikschneit wrote:
> Summary: OMAP patch causes SPI bus transaction failure on TI CPU 
> Commit: c859e0d479b3b4f6132fc12637c51e01492f31f6 Kernel version:
> 5.10.87
> 
> The detailed description:
> 
> I know this is a old commit at this point,

That shouldn't be a problem at all, but it raises one question that
would be good to get answered: does this problem still occur with the
latest code? This issue for example might have been fixed in between,
but maybe the fix was to complex to get backported or something like
that. Hence it would be ideal if you could quickly give 5.19-rc1 a shot;
5.18.y is not ideal, but will do as well.

> but we have observed a
> regression caused by this commit. It causes improper toggle during a
> SPI transaction with a microcontroller. The CPU in use is Texas
> Instruments AM3352BZCZA80. The microcontroller in use is a PIC based
> micro. I have logic capture images available to show the signal
> difference that is causing confusion on the SPI bus.

Ciao, Thorsten (wearing his 'the Linux kernel's regression tracker' hat)

P.S.: As the Linux kernel's regression tracker I deal with a lot of
reports and sometimes miss something important when writing mails like
this. If that's the case here, don't hesitate to tell me in a public
reply, it's in everyone's interest to set the public record straight.

Re: [REGRESSION] gpio: omap: ensure irq is enabled before wakeup

[Eric Schikschneit]

I am limited by the availability of the preempt-rt kernels that are 
available on the yocto project. The newest kernel I see listed is 
5.15.44 on: https://git.yoctoproject.org/linux-yocto/


From: Thorsten Leemhuis <regressions@leemhuis.info>
Sent: Tuesday, June 7, 2022 5:07 AM
To: Eric Schikschneit <eric.schikschneit@novatechautomation.com>; stable@vger.kernel.org <stable@vger.kernel.org>
Cc: regressions@lists.linux.dev <regressions@lists.linux.dev>; rmk+kernel@armlinux.org.uk <rmk+kernel@armlinux.org.uk>; grygorii.strashko@ti.com <grygorii.strashko@ti.com>; tony@atomide.com <tony@atomide.com>; linus.walleij@linaro.org <linus.walleij@linaro.org>
Subject: Re: [REGRESSION] gpio: omap: ensure irq is enabled before wakeup 
 
Hi, this is your Linux kernel regression tracker.

On 01.06.22 17:56, Eric Schikschneit wrote:
> Summary: OMAP patch causes SPI bus transaction failure on TI CPU 
> Commit: c859e0d479b3b4f6132fc12637c51e01492f31f6 Kernel version:
> 5.10.87
> 
> The detailed description:
> 
> I know this is a old commit at this point,

That shouldn't be a problem at all, but it raises one question that
would be good to get answered: does this problem still occur with the
latest code? This issue for example might have been fixed in between,
but maybe the fix was to complex to get backported or something like
that. Hence it would be ideal if you could quickly give 5.19-rc1 a shot;
5.18.y is not ideal, but will do as well.

> but we have observed a
> regression caused by this commit. It causes improper toggle during a
> SPI transaction with a microcontroller. The CPU in use is Texas
> Instruments AM3352BZCZA80. The microcontroller in use is a PIC based
> micro. I have logic capture images available to show the signal
> difference that is causing confusion on the SPI bus.

Ciao, Thorsten (wearing his 'the Linux kernel's regression tracker' hat)

P.S.: As the Linux kernel's regression tracker I deal with a lot of
reports and sometimes miss something important when writing mails like
this. If that's the case here, don't hesitate to tell me in a public
reply, it's in everyone's interest to set the public record straight.

Re: [REGRESSION] gpio: omap: ensure irq is enabled before wakeup

[Thorsten Leemhuis]

On 07.06.22 13:58, Eric Schikschneit wrote:
> I am limited by the availability of the preempt-rt kernels that are 
> available on the yocto project. The newest kernel I see listed is 
> 5.15.44 on: https://git.yoctoproject.org/linux-yocto/

Well, it's up to Russel if that is enough for him, as he authored
c859e0d479b3 ("gpio: omap: ensure irq is enabled before wakeup") and
thus should look into this regression.

Ciao, Thorsten

> From: Thorsten Leemhuis <regressions@leemhuis.info>
> Sent: Tuesday, June 7, 2022 5:07 AM
> To: Eric Schikschneit <eric.schikschneit@novatechautomation.com>; stable@vger.kernel.org <stable@vger.kernel.org>
> Cc: regressions@lists.linux.dev <regressions@lists.linux.dev>; rmk+kernel@armlinux.org.uk <rmk+kernel@armlinux.org.uk>; grygorii.strashko@ti.com <grygorii.strashko@ti.com>; tony@atomide.com <tony@atomide.com>; linus.walleij@linaro.org <linus.walleij@linaro.org>
> Subject: Re: [REGRESSION] gpio: omap: ensure irq is enabled before wakeup 
>  
> Hi, this is your Linux kernel regression tracker.
> 
> On 01.06.22 17:56, Eric Schikschneit wrote:
>> Summary: OMAP patch causes SPI bus transaction failure on TI CPU 
>> Commit: c859e0d479b3b4f6132fc12637c51e01492f31f6 Kernel version:
>> 5.10.87
>>
>> The detailed description:
>>
>> I know this is a old commit at this point,
> 
> That shouldn't be a problem at all, but it raises one question that
> would be good to get answered: does this problem still occur with the
> latest code? This issue for example might have been fixed in between,
> but maybe the fix was to complex to get backported or something like
> that. Hence it would be ideal if you could quickly give 5.19-rc1 a shot;
> 5.18.y is not ideal, but will do as well.
> 
>> but we have observed a
>> regression caused by this commit. It causes improper toggle during a
>> SPI transaction with a microcontroller. The CPU in use is Texas
>> Instruments AM3352BZCZA80. The microcontroller in use is a PIC based
>> micro. I have logic capture images available to show the signal
>> difference that is causing confusion on the SPI bus.
> 
> Ciao, Thorsten (wearing his 'the Linux kernel's regression tracker' hat)
> 
> P.S.: As the Linux kernel's regression tracker I deal with a lot of
> reports and sometimes miss something important when writing mails like
> this. If that's the case here, don't hesitate to tell me in a public
> reply, it's in everyone's interest to set the public record straight.

Re: [REGRESSION] gpio: omap: ensure irq is enabled before wakeup

[Russell King (Oracle)]

On Wed, Jun 08, 2022 at 10:54:48AM +0200, Thorsten Leemhuis wrote:
> On 07.06.22 13:58, Eric Schikschneit wrote:
> > I am limited by the availability of the preempt-rt kernels that are 
> > available on the yocto project. The newest kernel I see listed is 
> > 5.15.44 on: https://git.yoctoproject.org/linux-yocto/
> 
> Well, it's up to Russel if that is enough for him, as he authored
> c859e0d479b3 ("gpio: omap: ensure irq is enabled before wakeup") and
> thus should look into this regression.

I've already made it clear that is something I can no longer do; I
no longer have the knowledge, nor do I have the hardware to test
for this regression.

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
FTTP is here! 40Mbps down 10Mbps up. Decent connectivity at last!

Re: [REGRESSION] gpio: omap: ensure irq is enabled before wakeup

[Russell King (Oracle)]

On Wed, Jun 08, 2022 at 10:19:01AM +0100, Russell King (Oracle) wrote:
> On Wed, Jun 08, 2022 at 10:54:48AM +0200, Thorsten Leemhuis wrote:
> > On 07.06.22 13:58, Eric Schikschneit wrote:
> > > I am limited by the availability of the preempt-rt kernels that are 
> > > available on the yocto project. The newest kernel I see listed is 
> > > 5.15.44 on: https://git.yoctoproject.org/linux-yocto/
> > 
> > Well, it's up to Russel if that is enough for him, as he authored
> > c859e0d479b3 ("gpio: omap: ensure irq is enabled before wakeup") and
> > thus should look into this regression.
> 
> I've already made it clear that is something I can no longer do; I
> no longer have the knowledge, nor do I have the hardware to test
> for this regression.

There's a lot of debugging that needs to be done that can only be done
by the reporter to work out exactly what is going on. Most of what is
below is guess work - as I say, I don't have the knowledge, but what
follows is based on what would be a sensible investigation approach.

As I understand it having *briefly* looked at what I guess is the right
SPI code - I don't know - I'm guessing the CS lines are manually
controlled by the SPI driver via the GPIO layer.

If that is correct, the SPI driver must be itself deasserting the CS
line at the inappropriate point. This means the reporter needs to
locate where that is happening, and work out why the driver is doing
that. dump_stack() can be inserted at the appropriate point(s) to get
a stack trace to show the call path, which may or may not reveal how
we got there.

Also, we have no idea what the SPI device is, or how the driver for the
SPI device is using the SPI subsystem. Are there two separate transfers
being issued to the SPI subsystem, and is the CS signal being
deasserted between those two transfers?

If that is the case, deasserting the CS signal between the two
transfers seems to me to be entirely reasonable - as once a transfer
has completed, the SPI bus _could_ be used to access another peripheral
before the second transfer is acted upon. If this is the case, then
this commit has revealed a latent bug.

If CS is deasserted between two separate SPI transactions, but the chip
must not see CS deasserted, then that would be a bug in the SPI device
driver and have nothing to do with the GPIO layer. The change in the
GPIO code would have revealed a latent bug in the SPI side of things
(maybe the SPI device driver.)

There is just so much that is unknown here, and there is nothing I can
do here locally to debug this.

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
FTTP is here! 40Mbps down 10Mbps up. Decent connectivity at last!

Re: [REGRESSION] gpio: omap: ensure irq is enabled before wakeup #forregzbot

[Thorsten Leemhuis]

[TLDR: I'm adding this regression report to the list of tracked
regressions; all text from me you find below is based on a few templates
paragraphs you might have encountered already already in similar form.]

TWIMC: this mail is primarily send for documentation purposes and for
regzbot, my Linux kernel regression tracking bot. These mails usually
contain '#forregzbot' in the subject, to make them easy to spot and filter.

Hi, this is your Linux kernel regression tracker.

On 01.06.22 17:56, Eric Schikschneit wrote:
> Summary: OMAP patch causes SPI bus transaction failure on TI CPU
> Commit: c859e0d479b3b4f6132fc12637c51e01492f31f6
> Kernel version: 5.10.87
> 
> 
> The detailed description:
> 
> 
> I know this is a old commit at this point, but we have observed a regression caused by this commit. It causes improper toggle during a SPI transaction with a microcontroller. The CPU in use is Texas Instruments AM3352BZCZA80. The microcontroller in use is a PIC based micro. I have logic capture images available to show the signal difference that is causing confusion on the SPI bus.
> 

To be sure below issue doesn't fall through the cracks unnoticed, I'm
adding it to regzbot, my Linux kernel regression tracking bot:

#regzbot ^introduced c859e0d479b3b4f6132fc12637c51e01492f31f6
#regzbot title gpio: improper toggle during a SPI transaction with a
microcontroller
#regzbot ignore-activity
#regzbot back-burner: author of the commit can't help anymore

Ciao, Thorsten (wearing his 'the Linux kernel's regression tracker' hat)

P.S.: As the Linux kernel's regression tracker I deal with a lot of
reports and sometimes miss something important when writing mails like
this. If that's the case here, don't hesitate to tell me in a public
reply, it's in everyone's interest to set the public record straight.