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

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Date:   Tue, 19 Jan 2021 18:34:30 +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 Mon, Jan 18, 2021 at 03:02:38AM +0300, Dmitry Osipenko wrote:
> 15.01.2021 18:44, Thierry Reding пишет:
> > 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.
> 
> This is already fixed in v2. Good catch anyways, thanks.
> 
> > 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?
> 
> These are two independent changes. The previous patch fixed the missing
> resets, this patch changes the hardware initialization logic.

But moving to devm_reset_control_array_get_exclusive() isn't really part
of the hardware initialization logic change, right? So it's not strictly
related to the rest of this patch.

Anyway, I don't feel strongly about it being part of this patch, so feel
free to keep it here.

Thierry

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