linux-kernel - Re: [PATCH] ALSA: hda: Balance runtime/system PM if direct-complete is disabled

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Message-ID: <s5hzh16idnj.wl-tiwai@suse.de>
Date:   Mon, 18 Jan 2021 14:21:36 +0100
From:   Takashi Iwai <tiwai@...e.de>
To:     Kai-Heng Feng <kai.heng.feng@...onical.com>
Cc:     tiwai@...e.com, "Kenneth R . Crudup" <kenny@...ix.com>,
        Jaroslav Kysela <perex@...ex.cz>,
        Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>,
        Kai Vehmanen <kai.vehmanen@...ux.intel.com>,
        Ranjani Sridharan <ranjani.sridharan@...ux.intel.com>,
        Mark Brown <broonie@...nel.org>,
        Harsha Priya <harshapriya.n@...el.com>,
        alsa-devel@...a-project.org (moderated list:SOUND),
        linux-kernel@...r.kernel.org (open list)
Subject: Re: [PATCH] ALSA: hda: Balance runtime/system PM if direct-complete is disabled

On Mon, 18 Jan 2021 14:09:36 +0100,
Kai-Heng Feng wrote:
> 
> HDA controller can't be runtime-suspended after commit 215a22ed31a1
> ("ALSA: hda: Refactor codjc PM to use direct-complete optimization"),
> which enables direct-complete for HDA codec.
> 
> The HDA codec driver didn't expect direct-complete will be disabled
> after it returns a positive value from prepare() callback. However,
> there are some places that PM core can disable direct-complete. For
> instance, system hibernation or when codec has subordinates like LEDs.

Hmm.  This sounds rather like the approach using the direct-complete
isn't well suited for the purpose?  The increasing number of
regression reports worries me.

> So if a device is prepared for direct-complete but PM core still calls
> codec's suspend or freeze callback, resume the device to keep PM
> operations balanced.

I find the ping-pong of the resume/suspend there a bit odd.  It's no
refcount management but it invokes the real resume there, which is
involved with lots of operations.

Can we rather skip the hda_codec_suspend() call instead (while
changing dev->power.power_state)?


thanks,

Takashi

> Reported-by: Kenneth R. Crudup <kenny@...ix.com>
> Fixes: 215a22ed31a1 ("ALSA: hda: Refactor codec PM to use direct-complete optimization")
> Signed-off-by: Kai-Heng Feng <kai.heng.feng@...onical.com>
> ---
>  sound/pci/hda/hda_codec.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/sound/pci/hda/hda_codec.c b/sound/pci/hda/hda_codec.c
> index 687216e74526..0afbced979df 100644
> --- a/sound/pci/hda/hda_codec.c
> +++ b/sound/pci/hda/hda_codec.c
> @@ -2997,6 +2997,9 @@ static void hda_codec_pm_complete(struct device *dev)
>  
>  static int hda_codec_pm_suspend(struct device *dev)
>  {
> +	if (pm_runtime_status_suspended(dev))
> +		pm_runtime_resume(dev);
> +
>  	dev->power.power_state = PMSG_SUSPEND;
>  	return hda_codec_suspend(dev);
>  }
> @@ -3009,6 +3012,9 @@ static int hda_codec_pm_resume(struct device *dev)
>  
>  static int hda_codec_pm_freeze(struct device *dev)
>  {
> +	if (pm_runtime_status_suspended(dev))
> +		pm_runtime_resume(dev);
> +
>  	dev->power.power_state = PMSG_FREEZE;
>  	return hda_codec_suspend(dev);
>  }
> -- 
> 2.29.2
>