linux-kernel - Re: [PATCH v1 5/5] ASoC: tegra30: i2s: Add reset control

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Date:   Wed, 03 Mar 2021 13:09:46 +0100
From:   Philipp Zabel <p.zabel@...gutronix.de>
To:     Dmitry Osipenko <digetx@...il.com>,
        Thierry Reding <thierry.reding@...il.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Mark Brown <broonie@...nel.org>, Takashi Iwai <tiwai@...e.com>,
        Jaroslav Kysela <perex@...ex.cz>,
        Paul Fertser <fercerpav@...il.com>
Cc:     alsa-devel@...a-project.org, devicetree@...r.kernel.org,
        linux-tegra@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 5/5] ASoC: tegra30: i2s: Add reset control

Hi Dmitry,

On Wed, 2021-03-03 at 11:28 +0300, Dmitry Osipenko wrote:
> 02.03.2021 14:21, Dmitry Osipenko пишет:
> > The I2S reset may be asserted at a boot time. Tegra30 I2S driver doesn't
> > manage the reset control and currently it happens to work because reset
> > is implicitly deasserted by the Tegra AHUB driver, but the reset of I2C
> > controller should be synchronous and I2S clock is disabled when AHUB is
> > reset. Add reset control to the Tegra30 I2S driver.
> > 
> > Note that I2S reset was always specified in Tegra30+ device-trees, hence
> > DTB ABI changes aren't required. Also note that AHUB touches I2S resets,
> > hence AHUB resets are now requested in a released state, allowing both
> > drivers to control the I2S resets together.
> > 
> > Signed-off-by: Dmitry Osipenko <digetx@...il.com>
> > ---
> >  sound/soc/tegra/tegra30_ahub.c | 14 ++++++++++---
> >  sound/soc/tegra/tegra30_i2s.c  | 36 +++++++++++++++++++++++++++++++++-
> >  sound/soc/tegra/tegra30_i2s.h  |  1 +
> >  3 files changed, 47 insertions(+), 4 deletions(-)
> 
> ...
> > @@ -579,7 +587,7 @@ static int tegra30_ahub_probe(struct platform_device *pdev)
> >  	if (ret)
> >  		return ret;
> >  
> > -	ahub->reset = devm_reset_control_array_get_exclusive(&pdev->dev);
> > +	ahub->reset = devm_reset_control_array_get_exclusive_released(&pdev->dev);
> 
> Thinking a bit more about this, it looks like we actually want something
> like:
> 
> 	devm_reset_control_array_get_exclusive_released_named()
> 
> that will request resets by given names and in a given order, similarly
> to devm_clk_bulk_get(). This will be very handy for both Tegra audio and
> GPU drivers. I'll prepare a v2 if there are no objections.

I do have an untested reset control bulk API patch that I've just never
finished, because I had no user. I'll send you an RFC, let me know if
you can build on that.

regards
Philipp