linux-kernel - Re: [PATCH v3 06/19] ASoC: sun4i-i2s: Fix sun8i volatile regs

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Message-ID: <497a7062-4acf-d928-c2ee-ec595ed6799b@sholland.org>
Date:   Sun, 20 Sep 2020 13:52:11 -0500
From:   Samuel Holland <samuel@...lland.org>
To:     Clément Péron <peron.clem@...il.com>,
        Maxime Ripard <mripard@...nel.org>,
        Chen-Yu Tsai <wens@...e.org>, Rob Herring <robh+dt@...nel.org>,
        Mark Brown <broonie@...nel.org>,
        Liam Girdwood <lgirdwood@...il.com>
Cc:     Jaroslav Kysela <perex@...ex.cz>, Takashi Iwai <tiwai@...e.com>,
        Marcus Cooper <codekipper@...il.com>,
        Jernej Skrabec <jernej.skrabec@...l.net>,
        alsa-devel@...a-project.org, devicetree@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-sunxi@...glegroups.com
Subject: Re: [PATCH v3 06/19] ASoC: sun4i-i2s: Fix sun8i volatile regs

On 9/20/20 1:07 PM, Clément Péron wrote:
> The FIFO TX reg is volatile and sun8i i2s register
> mapping is different from sun4i.
> 
> Even if in this case it's doesn't create an issue,
> Avoid setting some regs that are undefined in sun8i.
> 
> Signed-off-by: Clément Péron <peron.clem@...il.com>
> Acked-by: Maxime Ripard <mripard@...nel.org>
> ---
>  sound/soc/sunxi/sun4i-i2s.c | 15 +++++++++++----
>  1 file changed, 11 insertions(+), 4 deletions(-)
> 
> diff --git a/sound/soc/sunxi/sun4i-i2s.c b/sound/soc/sunxi/sun4i-i2s.c
> index ce4913f0ffe4..a35be0e2baf5 100644
> --- a/sound/soc/sunxi/sun4i-i2s.c
> +++ b/sound/soc/sunxi/sun4i-i2s.c
> @@ -1126,12 +1126,19 @@ static bool sun8i_i2s_rd_reg(struct device *dev, unsigned int reg)
>  
>  static bool sun8i_i2s_volatile_reg(struct device *dev, unsigned int reg)
>  {
> -	if (reg == SUN8I_I2S_INT_STA_REG)
> +	switch (reg) {
> +	case SUN4I_I2S_FIFO_CTRL_REG:

Please check if this breaks audio recording with runtime PM enabled. I noticed
this with an older revision of the series that also changed
sun4i_i2s_volatile_reg. Marking SUN4I_I2S_FIFO_CTRL_REG as volatile broke
setting of SUN4I_I2S_FIFO_CTRL_TX_MODE/RX_MODE, because the set_fmt() callback
is not run with a runtime PM reference held, and volatile registers are not
written by regcache_sync() during sun4i_i2s_runtime_resume().

As a workaround, I moved the TX_MODE/RX_MODE initialization to hw_params(), but
I am not sure it is the right thing to do:

https://github.com/smaeul/linux/commit/5e40ac610986.patch

Cheers,
Samuel

> +	case SUN4I_I2S_FIFO_RX_REG:
> +	case SUN4I_I2S_FIFO_STA_REG:
> +	case SUN4I_I2S_RX_CNT_REG:
> +	case SUN4I_I2S_TX_CNT_REG:
> +	case SUN8I_I2S_FIFO_TX_REG:
> +	case SUN8I_I2S_INT_STA_REG:
>  		return true;
> -	if (reg == SUN8I_I2S_FIFO_TX_REG)
> -		return false;
>  
> -	return sun4i_i2s_volatile_reg(dev, reg);
> +	default:
> +		return false;
> +	}
>  }
>  
>  static const struct reg_default sun4i_i2s_reg_defaults[] = {
>