linux-kernel - Re: [PATCH v1 10/11] ALSA: hda: cs35l41: Add device_link between HDA and cs35l41

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Message-ID: <87v8eeiryp.wl-tiwai@suse.de>
Date:   Thu, 20 Jul 2023 16:21:34 +0200
From:   Takashi Iwai <tiwai@...e.de>
To:     Stefan Binding <sbinding@...nsource.cirrus.com>
Cc:     Mark Brown <broonie@...nel.org>, Jaroslav Kysela <perex@...ex.cz>,
        Takashi Iwai <tiwai@...e.com>, <alsa-devel@...a-project.org>,
        <linux-kernel@...r.kernel.org>, <patches@...nsource.cirrus.com>
Subject: Re: [PATCH v1 10/11] ALSA: hda: cs35l41: Add device_link between HDA and cs35l41_hda

On Thu, 20 Jul 2023 15:31:46 +0200,
Stefan Binding wrote:
> 
> To ensure consistency between the HDA core and the CS35L41 HDA
> driver, add a device_link between them. This ensures that the
> HDA core will suspend first, and resume second, meaning the
> amp driver will not miss any events from the playback hook from
> the HDA core during system suspend and resume.
> 
> Signed-off-by: Stefan Binding <sbinding@...nsource.cirrus.com>
> ---
>  sound/pci/hda/cs35l41_hda.c | 13 ++++++++++++-
>  1 file changed, 12 insertions(+), 1 deletion(-)
> 
> diff --git a/sound/pci/hda/cs35l41_hda.c b/sound/pci/hda/cs35l41_hda.c
> index 70aa819cfbd64..175378cdf9dfa 100644
> --- a/sound/pci/hda/cs35l41_hda.c
> +++ b/sound/pci/hda/cs35l41_hda.c
> @@ -1063,6 +1063,7 @@ static int cs35l41_hda_bind(struct device *dev, struct device *master, void *mas
>  {
>  	struct cs35l41_hda *cs35l41 = dev_get_drvdata(dev);
>  	struct hda_component *comps = master_data;
> +	unsigned int sleep_flags;
>  	int ret = 0;
>  
>  	if (!comps || cs35l41->index < 0 || cs35l41->index >= HDA_MAX_COMPONENTS)
> @@ -1102,6 +1103,11 @@ static int cs35l41_hda_bind(struct device *dev, struct device *master, void *mas
>  
>  	mutex_unlock(&cs35l41->fw_mutex);
>  
> +	sleep_flags = lock_system_sleep();
> +	if (!device_link_add(&comps->codec->core.dev, cs35l41->dev, DL_FLAG_STATELESS))
> +		dev_warn(dev, "Unable to create device link\n");
> +	unlock_system_sleep(sleep_flags);

Is lock_system_sleep() mandatory for device_link_add()?  The function
takes its rw lock for the race, I suppose.


thanks,

Takashi