linux-kernel - Re: [PATCH v1 5/5] ASoC: tegra: ahub: Reset hardware properly

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Date:   Fri, 15 Jan 2021 16:44:40 +0100
From:   Thierry Reding <thierry.reding@...il.com>
To:     Dmitry Osipenko <digetx@...il.com>
Cc:     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>,
        Jaroslav Kysela <perex@...ex.cz>, alsa-devel@...a-project.org,
        linux-tegra@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 5/5] ASoC: tegra: ahub: Reset hardware properly

On Tue, Jan 12, 2021 at 03:58:34PM +0300, Dmitry Osipenko wrote:
> Assert hardware reset before clocks are enabled and then de-assert it
> after clocks are enabled. This brings hardware into a predictable state
> and removes relying on implicit de-assertion of resets which is done by
> the clk driver.
> 
> Tested-by: Peter Geis <pgwipeout@...il.com>
> Tested-by: Nicolas Chauvet <kwizart@...il.com>
> Signed-off-by: Dmitry Osipenko <digetx@...il.com>
> ---
>  sound/soc/tegra/tegra30_ahub.c | 33 ++++++++++++++++-----------------
>  sound/soc/tegra/tegra30_ahub.h |  1 +
>  2 files changed, 17 insertions(+), 17 deletions(-)
> 
> diff --git a/sound/soc/tegra/tegra30_ahub.c b/sound/soc/tegra/tegra30_ahub.c
> index 4dbb58f7ea36..246cf6a373a1 100644
> --- a/sound/soc/tegra/tegra30_ahub.c
> +++ b/sound/soc/tegra/tegra30_ahub.c
> @@ -65,10 +65,20 @@ static int tegra30_ahub_runtime_resume(struct device *dev)
>  {
>  	int ret;
>  
> +	ret = reset_control_assert(ahub->reset);
> +	if (ret)
> +		return ret;
> +
>  	ret = clk_bulk_prepare_enable(ahub->nclocks, ahub->clocks);
>  	if (ret)
>  		return ret;
>  
> +	ret = reset_control_reset(ahub->reset);
> +	if (ret) {
> +		clk_bulk_disable_unprepare(ahub->nclocks, ahub->clocks);
> +		return ret;
> +	}
> +
>  	regcache_cache_only(ahub->regmap_apbif, false);
>  	regcache_cache_only(ahub->regmap_ahub, false);
>  
> @@ -462,7 +472,6 @@ static int tegra30_ahub_probe(struct platform_device *pdev)
>  {
>  	const struct of_device_id *match;
>  	const struct tegra30_ahub_soc_data *soc_data;
> -	struct reset_control *rst;
>  	struct resource *res0;
>  	void __iomem *regs_apbif, *regs_ahub;
>  	int ret = 0;
> @@ -475,22 +484,6 @@ static int tegra30_ahub_probe(struct platform_device *pdev)
>  		return -EINVAL;
>  	soc_data = match->data;
>  
> -	/*
> -	 * The AHUB hosts a register bus: the "configlink". For this to
> -	 * operate correctly, all devices on this bus must be out of reset.
> -	 * Ensure that here.
> -	 */
> -	rst = of_reset_control_array_get_exclusive(pdev->dev.of_node);
> -	if (IS_ERR(rst)) {
> -		dev_err(&pdev->dev, "Can't get reset: %p\n", rst);
> -		return PTR_ERR(rst);
> -	}
> -
> -	ret = reset_control_deassert(rst);
> -	reset_control_put(rst);
> -	if (ret)
> -		return ret;
> -
>  	ahub = devm_kzalloc(&pdev->dev, sizeof(struct tegra30_ahub),
>  			    GFP_KERNEL);
>  	if (!ahub)
> @@ -507,6 +500,12 @@ static int tegra30_ahub_probe(struct platform_device *pdev)
>  	if (ret)
>  		return ret;
>  
> +	ahub->reset = devm_reset_control_array_get_exclusive(&pdev->dev);
> +	if (IS_ERR(ahub->reset)) {
> +		dev_err(&pdev->dev, "Can't get reset: %p\n", ahub->reset);

I didn't notice that the prior patch already introduced this, but I'd
prefer for this to either be %pe so that the symbolic error name is
printed, or %ld with PTR_ERR(ahub->reset) to format this in a more
standard way that can be more easily grepped for and parsed.

It also seems like the prior patch that converts this to use
of_reset_control_array_get_exclusive() is a bit pointless now. Why not
just move to this directly instead?

Thierry

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