linux-kernel - Re: [PATCH v3 2/6] ALSA: hda/tegra: Reset hardware

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Date:   Mon, 25 Jan 2021 16:18:52 +0100
From:   Takashi Iwai <tiwai@...e.de>
To:     Dmitry Osipenko <digetx@...il.com>
Cc:     Thierry Reding <thierry.reding@...il.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Sameer Pujar <spujar@...dia.com>,
        Peter Geis <pgwipeout@...il.com>,
        Nicolas Chauvet <kwizart@...il.com>,
        Takashi Iwai <tiwai@...e.com>,
        Matt Merhar <mattmerhar@...tonmail.com>,
        Jaroslav Kysela <perex@...ex.cz>, alsa-devel@...a-project.org,
        linux-tegra@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 2/6] ALSA: hda/tegra: Reset hardware

On Wed, 20 Jan 2021 01:31:50 +0100,
Dmitry Osipenko wrote:
> 
> Reset hardware on RPM-resume in order to bring it into a predictable
> state.
> 
> Tested-by: Peter Geis <pgwipeout@...il.com> # Ouya T30 audio works
> Tested-by: Matt Merhar <mattmerhar@...tonmail.com> # Ouya T30 boot-tested
> Tested-by: Nicolas Chauvet <kwizart@...il.com> # TK1 boot-tested
> Signed-off-by: Dmitry Osipenko <digetx@...il.com>

Currently we have neither dependency nor reverse-selection of
CONFIG_RESET_CONTROLLER.  It wouldn't be a problem for builds, but
you'll get a runtime error from
devm_reset_control_array_get_exclusive() always when
CONFIG_RESET_CONTROLLER=n.

I guess it must be a corner case, but just to be sure.


thanks,

Takashi


> ---
>  sound/pci/hda/hda_tegra.c | 20 ++++++++++++++++++++
>  1 file changed, 20 insertions(+)
> 
> diff --git a/sound/pci/hda/hda_tegra.c b/sound/pci/hda/hda_tegra.c
> index a25bf7083c28..04dcd4cdfd9e 100644
> --- a/sound/pci/hda/hda_tegra.c
> +++ b/sound/pci/hda/hda_tegra.c
> @@ -17,6 +17,7 @@
>  #include <linux/moduleparam.h>
>  #include <linux/mutex.h>
>  #include <linux/of_device.h>
> +#include <linux/reset.h>
>  #include <linux/slab.h>
>  #include <linux/time.h>
>  #include <linux/string.h>
> @@ -70,6 +71,7 @@
>  struct hda_tegra {
>  	struct azx chip;
>  	struct device *dev;
> +	struct reset_control *reset;
>  	struct clk_bulk_data clocks[3];
>  	unsigned int nclocks;
>  	void __iomem *regs;
> @@ -167,6 +169,12 @@ static int __maybe_unused hda_tegra_runtime_resume(struct device *dev)
>  	struct hda_tegra *hda = container_of(chip, struct hda_tegra, chip);
>  	int rc;
>  
> +	if (!chip->running) {
> +		rc = reset_control_assert(hda->reset);
> +		if (rc)
> +			return rc;
> +	}
> +
>  	rc = clk_bulk_prepare_enable(hda->nclocks, hda->clocks);
>  	if (rc != 0)
>  		return rc;
> @@ -176,6 +184,12 @@ static int __maybe_unused hda_tegra_runtime_resume(struct device *dev)
>  		/* disable controller wake up event*/
>  		azx_writew(chip, WAKEEN, azx_readw(chip, WAKEEN) &
>  			   ~STATESTS_INT_MASK);
> +	} else {
> +		usleep_range(10, 100);
> +
> +		rc = reset_control_deassert(hda->reset);
> +		if (rc)
> +			return rc;
>  	}
>  
>  	return 0;
> @@ -441,6 +455,12 @@ static int hda_tegra_probe(struct platform_device *pdev)
>  		return err;
>  	}
>  
> +	hda->reset = devm_reset_control_array_get_exclusive(&pdev->dev);
> +	if (IS_ERR(hda->reset)) {
> +		err = PTR_ERR(hda->reset);
> +		goto out_free;
> +	}
> +
>  	hda->clocks[hda->nclocks++].id = "hda";
>  	hda->clocks[hda->nclocks++].id = "hda2hdmi";
>  	hda->clocks[hda->nclocks++].id = "hda2codec_2x";
> -- 
> 2.29.2
>