Nokia N900 OFF mode regression between v5.10 and v5.11

Nokia N900 OFF mode regression between v5.10 and v5.11

[Merlijn Wajer]

Hi Tony, Adam,

I noticed that after I fixed the OFF mode regression between v5.9 and
v5.10 that there are another one between v5.10 and v5.11. Fortunately,
much like the other change it can be worked around with a config change,
and in fact it looks like the commit identified by git bisect is indeed
just a commit to change omap2plus_defconfig.

a82820fcd079e38309403f595f005a8cc318a13c ("ARM: omap2plus_defconfig:
Enable OMAP3_THERMAL") prevents the N900 from entering OFF mode pretty
much all the time (I've seen scenarios with OFF:2,RET:500), but with the
config change reverted, stuff like this is more common: OFF:13,RET:2

We will probably to keep the thermal features enabled, but maybe we can
figure out why it causes the SoC to not enter sleep modes?

The good news is that this seems to be one of the last regressions with
regards to OFF mode (there might be smaller ones that cause slightly
more wakeups, but those will be harder to find). With this
(CONFIG_OMAP3_THERMAL) config option disabled as well; as fixes from my
other recent emails I can get my 5.15 branch to enter OFF mode again:

> # uname -a
> Linux (none) 5.15.2-00597-g68be8fac7cbd #48 SMP PREEMPT Sat Dec 11 00:14:05 CET 2021 armv7l GNU/Linux
> # grep ^core_pwrdm /sys/kernel/debug/pm_debug/count | cut -d',' -f2,
> OFF:13,RET:10

Regards,
Merlijn

Re: Nokia N900 OFF mode regression between v5.10 and v5.11

[Andreas Kemnade]

Hi,

On Sat, 11 Dec 2021 00:20:24 +0100
Merlijn Wajer <merlijn@wizzup.org> wrote:

> Hi Tony, Adam,
> 
> I noticed that after I fixed the OFF mode regression between v5.9 and
> v5.10 that there are another one between v5.10 and v5.11. Fortunately,
> much like the other change it can be worked around with a config change,
> and in fact it looks like the commit identified by git bisect is indeed
> just a commit to change omap2plus_defconfig.
> 
> a82820fcd079e38309403f595f005a8cc318a13c ("ARM: omap2plus_defconfig:
> Enable OMAP3_THERMAL") prevents the N900 from entering OFF mode pretty
> much all the time (I've seen scenarios with OFF:2,RET:500), but with the
> config change reverted, stuff like this is more common: OFF:13,RET:2
> 
> We will probably to keep the thermal features enabled, but maybe we can
> figure out why it causes the SoC to not enter sleep modes?

well, it was enabled after people agreed that is fixed... including me.
It was wrongly enabled some time before, then disabled again, fixed and
reenabled.
The mentioned commit was just after the fix. So what is different now?

Regards,
Andreas

Re: Nokia N900 OFF mode regression between v5.10 and v5.11

[Merlijn Wajer]

Hi Andreas,

On 11/12/2021 08:54, Andreas Kemnade wrote:
> Hi,
> 
> On Sat, 11 Dec 2021 00:20:24 +0100
> Merlijn Wajer <merlijn@wizzup.org> wrote:
> 
>> Hi Tony, Adam,
>>
>> I noticed that after I fixed the OFF mode regression between v5.9 and
>> v5.10 that there are another one between v5.10 and v5.11. Fortunately,
>> much like the other change it can be worked around with a config change,
>> and in fact it looks like the commit identified by git bisect is indeed
>> just a commit to change omap2plus_defconfig.
>>
>> a82820fcd079e38309403f595f005a8cc318a13c ("ARM: omap2plus_defconfig:
>> Enable OMAP3_THERMAL") prevents the N900 from entering OFF mode pretty
>> much all the time (I've seen scenarios with OFF:2,RET:500), but with the
>> config change reverted, stuff like this is more common: OFF:13,RET:2
>>
>> We will probably to keep the thermal features enabled, but maybe we can
>> figure out why it causes the SoC to not enter sleep modes?
> 
> well, it was enabled after people agreed that is fixed... including me.
> It was wrongly enabled some time before, then disabled again, fixed and
> reenabled.
> The mentioned commit was just after the fix. So what is different now?

I'll have to find the mails you are referring to, but I suspect that if
the device wasn't hitting OFF mode on v5.10 because of the
CONFIG_COMPACT=y option in omap2plus_defconfig, it might have masked
this issue?

Regards,
Merlijn

Re: Nokia N900 OFF mode regression between v5.10 and v5.11

[Andreas Kemnade]

Hi,

On Sat, 11 Dec 2021 11:23:33 +0100
Merlijn Wajer <merlijn@wizzup.org> wrote:

> Hi Andreas,
> 
> On 11/12/2021 08:54, Andreas Kemnade wrote:
> > Hi,
> > 
> > On Sat, 11 Dec 2021 00:20:24 +0100
> > Merlijn Wajer <merlijn@wizzup.org> wrote:
> >   
> >> Hi Tony, Adam,
> >>
> >> I noticed that after I fixed the OFF mode regression between v5.9 and
> >> v5.10 that there are another one between v5.10 and v5.11. Fortunately,
> >> much like the other change it can be worked around with a config change,
> >> and in fact it looks like the commit identified by git bisect is indeed
> >> just a commit to change omap2plus_defconfig.
> >>
> >> a82820fcd079e38309403f595f005a8cc318a13c ("ARM: omap2plus_defconfig:
> >> Enable OMAP3_THERMAL") prevents the N900 from entering OFF mode pretty
> >> much all the time (I've seen scenarios with OFF:2,RET:500), but with the
> >> config change reverted, stuff like this is more common: OFF:13,RET:2
> >>
> >> We will probably to keep the thermal features enabled, but maybe we can
> >> figure out why it causes the SoC to not enter sleep modes?  
> > 
> > well, it was enabled after people agreed that is fixed... including me.
> > It was wrongly enabled some time before, then disabled again, fixed and
> > reenabled.
> > The mentioned commit was just after the fix. So what is different now?  
> 
> I'll have to find the mails you are referring to, but I suspect that if
> the device wasn't hitting OFF mode on v5.10 because of the
> CONFIG_COMPACT=y option in omap2plus_defconfig, it might have masked
> this issue?
>
The patch fixing thermal power management is: 
 
commit 5093402e5b449b64f7bbaa09057ce40a8f3c1484
Author: Adam Ford <aford173@gmail.com>
Date:   Fri Sep 11 07:31:56 2020 -0500

    thermal: ti-soc-thermal: Enable addition power management
    
    The bandgap sensor can be idled when the processor is too, but it
    isn't currently being done, so the power consumption of OMAP3
    boards can elevated if the bangap sensor is enabled.
    
    This patch attempts to use some additional power management
    to idle the clock to the bandgap when not needed.

Maybe there is something specific to the N900 which causes these
issues? Well, I'll recheck on the boards I have.

Regards,
Andreas

Re: Nokia N900 OFF mode regression between v5.10 and v5.11

[Tony Lindgren]

Hi,

* Andreas Kemnade <andreas@kemnade.info> [211211 10:43]:
> The patch fixing thermal power management is: 
>  
> commit 5093402e5b449b64f7bbaa09057ce40a8f3c1484
> Author: Adam Ford <aford173@gmail.com>
> Date:   Fri Sep 11 07:31:56 2020 -0500
> 
>     thermal: ti-soc-thermal: Enable addition power management
>     
>     The bandgap sensor can be idled when the processor is too, but it
>     isn't currently being done, so the power consumption of OMAP3
>     boards can elevated if the bangap sensor is enabled.
>     
>     This patch attempts to use some additional power management
>     to idle the clock to the bandgap when not needed.
> 
> Maybe there is something specific to the N900 which causes these
> issues? Well, I'll recheck on the boards I have.

My guess the issue is that omap3-thermal needs to constantly poll
for the registers to get the status and that blocks any deeper
idle states. For PM, probably omap3-thermal needs to be tagged with
status = "disabled" assuming there is some other external thermal
sensor. I'm also guessing that the old Nokia kernel never used the
integrated thermal sensor, might be worth checking though.

Regards,

Tony

Re: Nokia N900 OFF mode regression between v5.10 and v5.11

[Merlijn Wajer]

On 11/12/2021 11:23, Merlijn Wajer wrote:
> Hi Andreas,
> 
> On 11/12/2021 08:54, Andreas Kemnade wrote:
>> Hi,
>>
>> On Sat, 11 Dec 2021 00:20:24 +0100
>> Merlijn Wajer <merlijn@wizzup.org> wrote:
>>
>>> Hi Tony, Adam,
>>>
>>> I noticed that after I fixed the OFF mode regression between v5.9 and
>>> v5.10 that there are another one between v5.10 and v5.11. Fortunately,
>>> much like the other change it can be worked around with a config change,
>>> and in fact it looks like the commit identified by git bisect is indeed
>>> just a commit to change omap2plus_defconfig.
>>>
>>> a82820fcd079e38309403f595f005a8cc318a13c ("ARM: omap2plus_defconfig:
>>> Enable OMAP3_THERMAL") prevents the N900 from entering OFF mode pretty
>>> much all the time (I've seen scenarios with OFF:2,RET:500), but with the
>>> config change reverted, stuff like this is more common: OFF:13,RET:2
>>>
>>> We will probably to keep the thermal features enabled, but maybe we can
>>> figure out why it causes the SoC to not enter sleep modes?
>>
>> well, it was enabled after people agreed that is fixed... including me.
>> It was wrongly enabled some time before, then disabled again, fixed and
>> reenabled.
>> The mentioned commit was just after the fix. So what is different now?
> 
> I'll have to find the mails you are referring to, but I suspect that if
> the device wasn't hitting OFF mode on v5.10 because of the
> CONFIG_COMPACT=y option in omap2plus_defconfig, it might have masked
> this issue?

Correction: CONFIG_COMPAT=y is not in omap2plus_defconfig, but it does
get enabled by default since v5.10, so the above still holds.

Regards,
Merlijn