linux-kernel - Re: [PATCH] ALSA: hda/tegra: enable clock during probe

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Date:   Thu, 24 Jan 2019 20:08:23 +0100
From:   Takashi Iwai <tiwai@...e.de>
To:     "Sameer Pujar" <spujar@...dia.com>
Cc:     <pierre-louis.bossart@...ux.intel.com>, <perex@...ex.cz>,
        <alsa-devel@...a-project.org>, <thierry.reding@...il.com>,
        <jonathanh@...dia.com>, <rlokhande@...dia.com>,
        <linux-kernel@...r.kernel.org>, <linux-tegra@...r.kernel.org>
Subject: Re: [PATCH] ALSA: hda/tegra: enable clock during probe

On Thu, 24 Jan 2019 18:36:43 +0100,
Sameer Pujar wrote:
> 
> If CONFIG_PM is disabled or runtime PM calls are forbidden, the clocks
> will not be ON. This could cause issue during probe, where hda init
> setup is done. This patch checks whether runtime PM is enabled or not.
> If disabled, clocks are enabled in probe() and disabled in remove()
> 
> This patch does following minor changes as cleanup,
>   * return code check for pm_runtime_get_sync() to take care of failure
>     and exit gracefully.
>   * In remove path runtime PM is disabled before calling snd_card_free().
>   * hda_tegra_disable_clocks() is moved out of CONFIG_PM_SLEEP check.
>   * runtime PM callbacks moved out of CONFIG_PM check
> 
> Signed-off-by: Sameer Pujar <spujar@...dia.com>
> Reviewed-by: Ravindra Lokhande <rlokhande@...dia.com>
> Reviewed-by: Jon Hunter <jonathanh@...dia.com>
(snip)
> @@ -555,6 +553,13 @@ static int hda_tegra_probe(struct platform_device *pdev)
>  	if (!azx_has_pm_runtime(chip))
>  		pm_runtime_forbid(hda->dev);
>  
> +	/* explicit resume if runtime PM is disabled */
> +	if (!pm_runtime_enabled(hda->dev)) {
> +		err = hda_tegra_runtime_resume(hda->dev);
> +		if (err)
> +			goto out_free;
> +	}
> +
>  	schedule_work(&hda->probe_work);

Calling runtime_resume here is really confusing...


> @@ -571,7 +576,14 @@ static void hda_tegra_probe_work(struct work_struct *work)
>  	struct platform_device *pdev = to_platform_device(hda->dev);
>  	int err;
>  
> -	pm_runtime_get_sync(hda->dev);
> +	err = pm_runtime_get_sync(hda->dev);
> +	if (err < 0) {
> +		dev_err(hda->dev,
> +			"failed in pm_runtime_get_syc with err = %d\n",
> +			err);
> +		return;
> +	}

This pm_runtime_get_sync() is needed just because you enabled runtime
PM before probe_work.  Why not deferring the runtime PM enablement
after probing done?

That is what we need is the hda_tegra_enable_clocks() call at probe
unconditionally before enabling runtime PM.

>  	err = hda_tegra_first_init(chip, pdev);
>  	if (err < 0)
>  		goto out_free;
> @@ -599,12 +611,13 @@ static void hda_tegra_probe_work(struct work_struct *work)
>  
>  static int hda_tegra_remove(struct platform_device *pdev)
>  {
> -	int ret;
> -
> -	ret = snd_card_free(dev_get_drvdata(&pdev->dev));
>  	pm_runtime_disable(&pdev->dev);
> +	if (!pm_runtime_status_suspended(&pdev->dev)) {
> +		hda_tegra_runtime_suspend(&pdev->dev);
> +		pm_runtime_set_suspended(&pdev->dev);
> +	}
> -	return ret;
> +	return snd_card_free(dev_get_drvdata(&pdev->dev));


Forcing the suspend *before* snd_card_free() doesn't sound right.
It's the point before the disconnect and release procedure of all the
rest.  That is, the other hardware components are still active at this
point.


thanks,

Takashi