Re: Regression found (Stop-marking-clocks-as-CLK_IS_CRITICAL)

[Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>]

On 10/30/18 9:38 AM, Dean Wallace wrote:
> On 30-10-18, Hans de Goede wrote:
>> Hi Dean,
>>
>> Attached are 2 different attempts at fixing this.
>>
>> When trying these patches do not forget to remove the revert of the
>> "Stop-marking-clocks-as-CLK_IS_CRITICAL" commit.
>>
>> Please first try the 0001-ASoC-intel-cht_bsw_max98090_ti-Use-pmc_plt_clk_0-ins.patch
>> patch I expect that one to do the trick indicating that the Swanky model
>> uses a different pmc clk then which is normally used for the codec clock.
>>
>> If that patch does not fix things, please give the other patch a try.

For Baytrail devices, the audio platform clocks are not managed by the 
firmware. They are for CHT-based devices - as can be seen by clock 
resources being described in the DSDT. We used to have a if(baytrail) in 
the code which was replaced by this CRITICAL label, but the point 
remains that there is a difference between the two SOC versions.

In addition I am not aware of any baytrail device using plt_clk_0, so 
moving a common machine driver such a cht_bsw_max98090_ti to use 
plt_clk0 only would break other devices (e.g. Rambi/Orco). Asking for 
both clocks to be on might work though, however you still have the 
problem of trying to manage from the kernel what the firmware already 
manages.

>>
>> Regards,
>>
>> Hans
>>
>>
>>
>> On 29-10-18 23:03, Pierre-Louis Bossart wrote:
>>> On 10/29/18 2:08 PM, Dean Wallace wrote:
>>>> On 29-10-18, Andy Shevchenko wrote:
>>>>> On Mon, Oct 29, 2018 at 7:52 PM Andy Shevchenko
>>>>> <andy.shevchenko@gmail.com> wrote:
>>>>>> Cc: Pierre as well.
>>>>>>
>>>>>> On Mon, Oct 29, 2018 at 7:48 PM Stephen Boyd <sboyd@kernel.org> wrote:
>>>>>>> Quoting Dean Wallace (2018-10-25 16:25:17)
>>>>>>>> I have found a regression in 4.18.15 that means I lose sound on my old
>>>>>>>> Toshiba Chromebook 2 (Swanky).  My system details are:-
>>>>>>>>
>>>>>>>> Toshiba Chromebook (Swanky)
>>>>>>>> MrChromebox UEFI coreboot
>>>>>>>> Arch Linux running latest alsa/pulseaudio
>>>>>>>>
>>>>>>>> Upgraded kernel from 4.18.14 to 4.18.15 and lost all sound output.  By
>>>>>>>> output I mean, the card is still detected, the module loaded, all apps
>>>>>>>> showing sound is being playing, but no actual audible sound comes
>>>>>>>> through.  Upgraded to 4.18.16 same issue.
>>>>>>>>
>>>>>>>> Dug around and found Upstream commit 648e921888ad96ea3dc922739e96716ad3225d7f
>>>>>>>> clk: x86: Stop marking clocks as CLK_IS_CRITICAL
>>>>>>>> "This commit removes the CLK_IS_CRITICAL marking, fixing Cherry Trail
>>>>>>>> devices not being able to reach S0i3 greatly decreasing their battery
>>>>>>>> drain when suspended."
>>>>>>>>
>>>>>>>> I reverted it and compiled 4.18.16 and have sound back again.  Could
>>>>>>>> this be looked into, with possibility of fix.
>>>>>>>>
>>>>>>> Thanks for the bug report. I'm adding some people involved in the commit
>>>>>>> you mention is causing audio regressions. The best plan is to probably
>>>>>>> revert the commit from the 4.18 linux stable tree. Or there may be
>>>>>>> another patch missing that would be useful to make this backported patch
>>>>>>> work. Hopefully Hans or Andy knows.
>>>>>> Hans has been investigating S0ix issues on Baytrail and Cherrytrail machines.
>>>>>> I have a feeling that the problem can be fixed by properly handling
>>>>>> clock in ASoC driver(s). Perhaps Hans and Pierre can figure this out
>>>>>> better than me.
>>>>> Looking to sound/soc/intel/boards/cht_bsw_rt5672.c I see no
>>>>> suspend-resume hooks. Perhaps, adding them like in the commit
>>>>> ac8bd9e13be2 ("r8169: Disable clk during suspend / resume") would
>>>>> help.
>>> I missed this change while i was away. It's indeed the expectation that the audio mclk is handled by the firmware,
>> I believe that the statement "It's indeed the expectation that the
>> audio mclk is handled by the firmware" is not correct for BYT/CHT
>> platforms (and the commit causing the regression only affects BYT/CHT
>> platforms). Various machine drivers under sound/soc/intel/boards have
>> code to deal with the mclk themselves, like this:
>>
>>          drv->mclk = devm_clk_get(&pdev->dev, "pmc_plt_clk_3");
>> ...
>>
>>          if (SND_SOC_DAPM_EVENT_ON(event)) {
>>                  ret = clk_prepare_enable(ctx->mclk);
>> 		...
>>          } else {
>>                  clk_disable_unprepare(ctx->mclk);
>>          }
>>
>> The above code is from sound/soc/intel/boards/cht_bsw_max98090_ti.c
>> which is the machine driver used on the machines for which problems
>> are now being reported.
>>
>> And my commit introducing the problem is in essence a revert of:
>>
>> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit?id=d31fd43c0f9a41e2678a1e78c0f22f0384c6edd3
>>
>> Which is from 2017-07-14 and the ASoC code for BYT/CHT platforms is
>> much older then that.
>>
>> Also I asked Carlo why he wrote that patch and it was to fix a problem
>> with ethernet on some laptops.
>>
>>> not sure I understand why removing the CLK_IS_CRITICAL was necessary or what it has to do with S0ix.
>> It is necessary, because if it is set the clock never gets disabled and
>> on x86 platforms using suspend2idle we are responsible for *all* the hardware
>> power-management as OS. If we do not disable the clocks then we can only
>> reach S0i1 instead of S0i3 when suspended leading to increased battery
>> drain during suspend.
>>
>> Also note that this patch is only causing problems on CHT + max98090 codec
>> using machines. I've tested it on many other BYT/CHT machines myself and
>> we've not had any other bug reports related to this.
>>
>> So this clearly points to a problem with the clock management in the
>> cht_bsw_max98090_ti.c machine driver.
>>
>> I've some ideas how to fix this and I will prepare some patches to test.
>>
>> Regards,
>>
>> Hans
> Excellent work Hans.  Compiled 4.19 with
> 0001-ASoC-intel-cht_bsw_max98090_ti-Use-pmc_plt_clk_0-ins.patch, sound
> works as before.
>
> for i in /sys/kernel/debug/clk/pmc_plt_clk_?; do echo -n "$i: "; cat $i/clk_flags; echo; done
> /sys/kernel/debug/clk/pmc_plt_clk_0:
> /sys/kernel/debug/clk/pmc_plt_clk_1:
> /sys/kernel/debug/clk/pmc_plt_clk_2:
> /sys/kernel/debug/clk/pmc_plt_clk_3:
> /sys/kernel/debug/clk/pmc_plt_clk_4:
> /sys/kernel/debug/clk/pmc_plt_clk_5:
>
> Regards