linux-kernel - Re: [PATCH v2] ALSA: hda/tegra: enable clock during probe

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Message-ID: <b631310f-93fa-ef4b-7014-d97fcfb2dcdf@nvidia.com>
Date:   Wed, 30 Jan 2019 12:45:49 +0000
From:   Jon Hunter <jonathanh@...dia.com>
To:     Sameer Pujar <spujar@...dia.com>, <perex@...ex.cz>,
        <tiwai@...e.com>, <pierre-louis.bossart@...ux.intel.com>
CC:     <thierry.reding@...il.com>, <rlokhande@...dia.com>,
        <sharadg@...dia.com>, <mkumard@...dia.com>,
        <alsa-devel@...a-project.org>, <linux-tegra@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] ALSA: hda/tegra: enable clock during probe


On 25/01/2019 11:06, 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 enables clocks unconditionally during probe.
> 
> Along with above, follwoing changes are done.
>   * enable runtime PM before exiting from probe work. This helps to avoid
>     usage of pm_runtime_get_sync/pm_runtime_put() in probe work.
>   * 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>
> ---
>  sound/pci/hda/hda_tegra.c | 26 +++++++++++++++++---------
>  1 file changed, 17 insertions(+), 9 deletions(-)
> 
> diff --git a/sound/pci/hda/hda_tegra.c b/sound/pci/hda/hda_tegra.c
> index c8d18dc..ba6175f 100644
> --- a/sound/pci/hda/hda_tegra.c
> +++ b/sound/pci/hda/hda_tegra.c
> @@ -219,7 +219,6 @@ static int hda_tegra_enable_clocks(struct hda_tegra *data)
>  	return rc;
>  }
>  
> -#ifdef CONFIG_PM_SLEEP
>  static void hda_tegra_disable_clocks(struct hda_tegra *data)
>  {
>  	clk_disable_unprepare(data->hda2hdmi_clk);
> @@ -227,6 +226,7 @@ static void hda_tegra_disable_clocks(struct hda_tegra *data)
>  	clk_disable_unprepare(data->hda_clk);
>  }
>  
> +#ifdef CONFIG_PM_SLEEP
>  /*
>   * power management
>   */
> @@ -257,7 +257,6 @@ static int hda_tegra_resume(struct device *dev)
>  }
>  #endif /* CONFIG_PM_SLEEP */
>  
> -#ifdef CONFIG_PM
>  static int hda_tegra_runtime_suspend(struct device *dev)
>  {
>  	struct snd_card *card = dev_get_drvdata(dev);
> @@ -283,7 +282,7 @@ static int hda_tegra_runtime_resume(struct device *dev)
>  	int rc;
>  
>  	rc = hda_tegra_enable_clocks(hda);
> -	if (rc != 0)
> +	if (rc)
>  		return rc;
>  	if (chip && chip->running) {
>  		hda_tegra_init(hda);
> @@ -292,7 +291,6 @@ static int hda_tegra_runtime_resume(struct device *dev)
>  
>  	return 0;
>  }
> -#endif /* CONFIG_PM */
>  
>  static const struct dev_pm_ops hda_tegra_pm = {
>  	SET_SYSTEM_SLEEP_PM_OPS(hda_tegra_suspend, hda_tegra_resume)
> @@ -551,9 +549,9 @@ static int hda_tegra_probe(struct platform_device *pdev)
>  
>  	dev_set_drvdata(&pdev->dev, card);
>  
> -	pm_runtime_enable(hda->dev);
> -	if (!azx_has_pm_runtime(chip))
> -		pm_runtime_forbid(hda->dev);
> +	err = hda_tegra_enable_clocks(hda);
> +	if (err)
> +		goto out_free;

We also need to think about power-domains here. Enabling the clocks
might not be enough as the appropriate power-domain needs to be enabled.
For 64-bit Tegra runtime-pm will handle the power-domains (assuming they
are populated in device-tree). So I still think it is better we call
pm_runtime_get_sync() at some point rather than just replying on
enabling the clocks.

Cheers
Jon

-- 
nvpublic