linux-kernel - Re: [PATCH v1] ASoC: rockchip: i2s: use regmap_read_poll_timeout to poll I2S

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Message-ID: <YyEj8FC9YtnCScWW@google.com>
Date:   Tue, 13 Sep 2022 17:44:32 -0700
From:   Brian Norris <briannorris@...omium.org>
To:     Judy Hsiao <judyhsiao@...omium.org>
Cc:     Liam Girdwood <lgirdwood@...il.com>,
        Mark Brown <broonie@...nel.org>,
        Jaroslav Kysela <perex@...ex.cz>,
        Takashi Iwai <tiwai@...e.com>,
        Chen-Yu Tsai <wenst@...omium.org>, alsa-devel@...a-project.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-rockchip@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1] ASoC: rockchip: i2s: use regmap_read_poll_timeout to
 poll I2S_CLR

Hi Judy,

On Thu, Sep 08, 2022 at 03:11:42PM +0000, Judy Hsiao wrote:
> Use regmap_read_poll_timeout to poll I2S_CLR.
> It also fixes the 'rockchip-i2s ff070000.i2s; fail to clear' and
> return -EBUSY when the read of I2S_CLR exceeds the retry limit.
> 
> Fixes: 0ff9f8b9f592 ("ASoC: rockchip: i2s: Fix error code when fail
> to read I2S_CLR")
> Signed-off-by: Judy Hsiao <judyhsiao@...omium.org>

Thanks for the patch!

> ---
>  sound/soc/rockchip/rockchip_i2s.c | 39 +++++++++++++------------------
>  1 file changed, 16 insertions(+), 23 deletions(-)
> 
> diff --git a/sound/soc/rockchip/rockchip_i2s.c b/sound/soc/rockchip/rockchip_i2s.c
> index f5f3540a9e18..02905eec615e 100644
> --- a/sound/soc/rockchip/rockchip_i2s.c
> +++ b/sound/soc/rockchip/rockchip_i2s.c
> @@ -163,18 +163,14 @@ static int rockchip_snd_txctrl(struct rk_i2s_dev *i2s, int on)
>  						 I2S_CLR_TXC | I2S_CLR_RXC);
>  			if (ret < 0)
>  				goto end;
> -			regmap_read(i2s->regmap, I2S_CLR, &val);
> -
> -			/* Should wait for clear operation to finish */
> -			while (val) {
> -				regmap_read(i2s->regmap, I2S_CLR, &val);
> -				retry--;

I think you're leaving |retry| as a "set but unused" variable now.
Presumably some compile-testing bots will eventually complain at you
about that.

> -				if (!retry) {
> -					dev_warn(i2s->dev, "fail to clear\n");
> -					ret = -EBUSY;
> -					break;
> -				}
> -			}
> +			ret = regmap_read_poll_timeout(i2s->regmap,
> +						       I2S_CLR,
> +						       val,
> +						       val != 0,
> +						       20,
> +						       200);
> +			if (ret < 0)
> +				dev_warn(i2s->dev, "fail to clear\n");

Now would be a good time to print the return code, I think:

				dev_warn(i2s->dev, "fail to clear: %d\n", ret);

>  		}
>  	}
>  end:
> @@ -226,17 +222,14 @@ static int rockchip_snd_rxctrl(struct rk_i2s_dev *i2s, int on)
>  						 I2S_CLR_TXC | I2S_CLR_RXC);
>  			if (ret < 0)
>  				goto end;
> -			regmap_read(i2s->regmap, I2S_CLR, &val);
> -			/* Should wait for clear operation to finish */
> -			while (val) {
> -				regmap_read(i2s->regmap, I2S_CLR, &val);
> -				retry--;
> -				if (!retry) {

Same.

> -					dev_warn(i2s->dev, "fail to clear\n");
> -					ret = -EBUSY;
> -					break;
> -				}
> -			}
> +			ret = regmap_read_poll_timeout(i2s->regmap,
> +						       I2S_CLR,
> +						       val,
> +						       val != 0,
> +						       20,
> +						       200);
> +			if (ret < 0)
> +				dev_warn(i2s->dev, "fail to clear\n");

Same.

>  		}
>  	}
>  end:

Otherwise, this is definitely a good change, since we have no timing
guarantee on the existing retry loop, which will surely make it flaky.
So, with those fixups:

Reviewed-by: Brian Norris <briannorris@...omium.org>