linux-kernel - Re: [PATCH] ASoC: cros_ec_codec: Reset I2S RX when probing

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Date:   Wed, 8 Jul 2020 06:28:02 -0700
From:   Guenter Roeck <groeck@...gle.com>
To:     Enric Balletbo i Serra <enric.balletbo@...labora.com>
Cc:     Yu-Hsuan Hsu <yuhsuan@...omium.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Benson Leung <bleung@...omium.org>,
        Guenter Roeck <groeck@...omium.org>,
        Cheng-Yi Chiang <cychiang@...omium.org>,
        Liam Girdwood <lgirdwood@...il.com>,
        Mark Brown <broonie@...nel.org>,
        Jaroslav Kysela <perex@...ex.cz>,
        Takashi Iwai <tiwai@...e.com>,
        Tzung-Bi Shih <tzungbi@...gle.com>,
        Gwendal Grignou <gwendal@...omium.org>,
        Lee Jones <lee.jones@...aro.org>,
        Yicheng Li <yichengli@...omium.org>,
        ALSA development <alsa-devel@...a-project.org>
Subject: Re: [PATCH] ASoC: cros_ec_codec: Reset I2S RX when probing

On Wed, Jul 8, 2020 at 3:16 AM Enric Balletbo i Serra
<enric.balletbo@...labora.com> wrote:
>
> Hi Yu-Hsuan,
>
> Thank you for your patch.
>
> On 8/7/20 9:11, Yu-Hsuan Hsu wrote:
> > It is not guaranteed that I2S RX is disabled when the kernel booting.
> > For example, if the kernel crashes while it is enabled, it will keep
> > enabled until the next time EC reboots. Reset I2S RX when probing to
> > fix this issue.
> >
> > Signed-off-by: Yu-Hsuan Hsu <yuhsuan@...omium.org>
> > ---
> >  include/linux/platform_data/cros_ec_commands.h | 1 +
> >  sound/soc/codecs/cros_ec_codec.c               | 7 +++++++
> >  2 files changed, 8 insertions(+)
> >
> > diff --git a/include/linux/platform_data/cros_ec_commands.h b/include/linux/platform_data/cros_ec_commands.h
> > index 69210881ebac8..11ce917ca924c 100644
> > --- a/include/linux/platform_data/cros_ec_commands.h
> > +++ b/include/linux/platform_data/cros_ec_commands.h
> > @@ -4598,6 +4598,7 @@ enum ec_codec_i2s_rx_subcmd {
> >       EC_CODEC_I2S_RX_SET_SAMPLE_DEPTH = 0x2,
> >       EC_CODEC_I2S_RX_SET_DAIFMT = 0x3,
> >       EC_CODEC_I2S_RX_SET_BCLK = 0x4,
> > +     EC_CODEC_I2S_RX_RESET = 0x5,
>
> Is this a new command not available in the firmware that is already in the field?
>
>
> >       EC_CODEC_I2S_RX_SUBCMD_COUNT,
> >  };
> >
> > diff --git a/sound/soc/codecs/cros_ec_codec.c b/sound/soc/codecs/cros_ec_codec.c
> > index 8d45c628e988e..5495214e73e68 100644
> > --- a/sound/soc/codecs/cros_ec_codec.c
> > +++ b/sound/soc/codecs/cros_ec_codec.c
> > @@ -1034,6 +1034,13 @@ static int cros_ec_codec_platform_probe(struct platform_device *pdev)
> >       }
> >       priv->ec_capabilities = r.capabilities;
> >
> > +     /* Reset EC codec I2S RX. */
> > +     p.cmd = EC_CODEC_I2S_RX_RESET;
> > +     ret = send_ec_host_command(priv->ec_device, EC_CMD_EC_CODEC_I2S_RX,
> > +                                (uint8_t *)&p, sizeof(p), NULL, 0);
> > +     if (ret)
> > +             dev_err(dev, "failed to EC_CODEC_I2S_RESET: %d\n", ret);
> > +
>
> With an old firmware I suspect this message will appear on every boot, right?
> So, to solve the issue and get rid of this error you're forced to upgrade the
> firmware. Is that true?
>

It might possibly make more sense to fail this silently and to send
EC_CODEC_I2S_RX_DISABLE as backup if it is not supported (-ENOTSUPP
can possibly be used as trigger if the call returns it).

Also, I don't accept dev_err() if the error is ignored for patches in
my scope of responsibility.

Guenter

> >       platform_set_drvdata(pdev, priv);
> >
> >       ret = devm_snd_soc_register_component(dev, &i2s_rx_component_driver,
> >