Re: HDA, power saving and recording

["Amadeusz Sławiński" <amadeuszx.slawinski@linux.intel.com>]

On 5/12/2023 2:24 PM, Takashi Iwai wrote:
> On Fri, 12 May 2023 14:00:54 +0200,
> Amadeusz Sławiński wrote:
>>
>> On 5/12/2023 1:33 PM, Takashi Iwai wrote:
>>> On Fri, 12 May 2023 13:23:49 +0200,
>>> Takashi Iwai wrote:
>>>>
>>>> On Thu, 11 May 2023 19:20:17 +0200,
>>>> Amadeusz Sławiński wrote:
>>>>>
>>>>> On 5/11/2023 5:58 PM, Takashi Iwai wrote:
>>>>>> On Thu, 11 May 2023 17:31:37 +0200,
>>>>>> Amadeusz Sławiński wrote:
>>>>>>>
>>>>>>> On 5/10/2023 2:21 PM, Takashi Iwai wrote:
>>>>>>>> On Tue, 09 May 2023 12:10:06 +0200,
>>>>>>>> Amadeusz Sławiński wrote:
>>>>>>> Then capture stream starts and seems to assume that
>>>>>>> registers were already set, so it doesn't write them to hw.
>>>>>>
>>>>>> ... it seems this didn't happen, and that's the inconsistency.
>>>>>>
>>>>>> So the further question is:
>>>>>> At the point just before you start recording, is the codec in runtime
>>>>>> suspended?  Or it's running?
>>>>>>
>>>>>> If it's runtime-suspended, snd_hda_regmap_sync() must be called from
>>>>>> alc269_resume() via runtime-resume, and this must write out the
>>>>>> cached values.  Then the bug can be along with that line.
>>>>>>
>>>>>> Or if it's running, it means that the previous check of
>>>>>> snd_hdac_keep_power_up() was bogus (or racy).
>>>>>>
>>>>>
>>>>> Well, it is in... let's call it semi powered state. When snd_hda_intel
>>>>> driver is loaded with power_save=X option it sets timeout to X seconds
>>>>> and problem only happens when I start the stream before those X
>>>>> seconds pass and it runs first runtime suspend. After it suspends it
>>>>> then uses standard pm_runtime_resume and works correctly. That's why
>>>>> the pm_runtime_force_suspend(&codec->core.dev);  mentioned in first
>>>>> email in thread "fixes" the problem, as it forces it to be instantly
>>>>> suspended instead of waiting for timeout and then later normal
>>>>> resume-play/record-suspend flow can be followed.
>>>>
>>>> Hm, then maybe it's a bad idea to rely on the usage count there.
>>>> Even if the usage is 0, the device can be still active, and the update
>>>> can be missed.
>>>>
>>>> How about the patch like below?
>>>
>>> Scratch that, it returns a wrong value.
>>> A simpler version like below works instead?
>>>
>>
>> Yes it was broken, arecord didn't even start capturing ;)
>>
>>>
>>> Takashi
>>>
>>> --- a/sound/hda/hdac_device.c
>>> +++ b/sound/hda/hdac_device.c
>>> @@ -611,10 +611,9 @@ EXPORT_SYMBOL_GPL(snd_hdac_power_up_pm);
>>>    int snd_hdac_keep_power_up(struct hdac_device *codec)
>>>    {
>>>    	if (!atomic_inc_not_zero(&codec->in_pm)) {
>>> -		int ret = pm_runtime_get_if_in_use(&codec->dev);
>>> -		if (!ret)
>>> +		if (!pm_runtime_active(&codec->dev))
>>>    			return -1;
>>> -		if (ret < 0)
>>> +		if (pm_runtime_get_sync(&codec->dev) < 0)
>>>    			return 0;
>>>    	}
>>>    	return 1;
>>
>>
>> This one seems to work, as in I'm able to record before first suspend
>> hits. However device stays in D0 when no stream is running...
>> # cat /sys/devices/pci0000\:00/0000\:00\:0e.0/power_state
>> D0
> 
> OK, one step forward.  The previous change was bad in anyway, as we
> shouldn't sync there at all.
> 
> So, the problem becomes clearer now: it's in the lazy update mechanism
> that misses the case that has to be written.
> 
> Scratch the previous one again, and could you try the following one
> instead?
> 
> 
> Takashi
> 
> --- a/sound/hda/hdac_regmap.c
> +++ b/sound/hda/hdac_regmap.c
> @@ -293,8 +293,17 @@ static int hda_reg_write(void *context, unsigned int reg, unsigned int val)
>   
>   	if (verb != AC_VERB_SET_POWER_STATE) {
>   		pm_lock = codec_pm_lock(codec);
> -		if (pm_lock < 0)
> -			return codec->lazy_cache ? 0 : -EAGAIN;
> +		if (pm_lock < 0) {
> +			/* skip the actual write if it's in lazy-update mode
> +			 * and only if the device is actually suspended;
> +			 * the usage count can be zero at transition phase
> +			 * (either suspending/resuming or auto-suspend sleep)
> +			 */
> +			if (codec->lazy_cache &&
> +			    pm_runtime_suspended(&codec->dev))
> +				return 0;
> +			return -EAGAIN;
> +		}
>   	}
>   
>   	if (is_stereo_amp_verb(reg)) {
> 

With this one we are back to same behavior as without it. When capture 
is started before first suspend it records silence. After waiting for 
timeout and suspend it records correctly.