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

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Date:   Wed, 8 Jul 2020 10:25:54 -0700
From:   Guenter Roeck <groeck@...gle.com>
To:     Yu-Hsuan Hsu <yuhsuan@...omium.org>
Cc:     Enric Balletbo i Serra <enric.balletbo@...labora.com>,
        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 9:17 AM Yu-Hsuan Hsu <yuhsuan@...omium.org> wrote:
>
> Guenter Roeck <groeck@...gle.com> 於 2020年7月8日 週三 下午9:28寫道：
> >
> > 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
> Thanks for the suggestion. Our plan is to upstream this patch first.
> And then we will merge it into the kernel after the firmware is
> updated. Is it feasible? (I'm not sure whether there is the better way
> if I want to update EC and the kernel at the same time.)
>
> I think calling EC_CODEC_I2S_RX_DISABLE does not make sense because it
> checks the value of i2s_rx_enabled first. If i2s_rx_enabled is false,
> it will skip the function. However, we don't need to reset while the
> i2s_rx_enabled is already false.
>
Exactly my point. If i2s_rx_enabled is false, nothing needs to be
done, and it doesn't hurt if the EC does nothing. If i2s_rx_enabled is
true, it needs to be set to false, which is accomplished by sending
EC_CODEC_I2S_RX_DISABLE.

> In addition, since it is a sub-command, it will return
> EC_RES_INVALID_PARAM but not ENOTSUPP if the command is not supported.
> And then EC_RES_INVALID_PARAM will turn into -EPROTO finally so it's
> difficult to do other operators basing on the return value.
>

You might have to convince Enric to permit another error code to
translate EC_RES_INVALID_PARAM. After all, that would meet his
requirement that the error code must be used in the kernel to accept a
translation.

Guenter

> Thanks,
> Yu-Hsuan
>
> >
> > > >       platform_set_drvdata(pdev, priv);
> > > >
> > > >       ret = devm_snd_soc_register_component(dev, &i2s_rx_component_driver,
> > > >