linux-kernel - Re: [PATCH v2] ASoC: cros_ec_codec: Reset I2S RX when probing

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Date:   Thu, 16 Jul 2020 10:23:32 -0700
From:   Guenter Roeck <groeck@...gle.com>
To:     Yu-Hsuan Hsu <yuhsuan@...omium.org>
Cc:     linux-kernel <linux-kernel@...r.kernel.org>,
        Tzung-Bi Shih <tzungbi@...gle.com>,
        Cheng-Yi Chiang <cychiang@...omium.org>,
        Enric Balletbo i Serra <enric.balletbo@...labora.com>,
        Guenter Roeck <groeck@...omium.org>,
        Liam Girdwood <lgirdwood@...il.com>,
        Mark Brown <broonie@...nel.org>,
        Jaroslav Kysela <perex@...ex.cz>,
        Takashi Iwai <tiwai@...e.com>,
        Benson Leung <bleung@...omium.org>,
        ALSA development <alsa-devel@...a-project.org>
Subject: Re: [PATCH v2] ASoC: cros_ec_codec: Reset I2S RX when probing

On Thu, Jul 16, 2020 at 10:09 AM Yu-Hsuan Hsu <yuhsuan@...omium.org> 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>
> ---
>  drivers/platform/chrome/cros_ec_proto.c        | 7 ++++++-
>  include/linux/platform_data/cros_ec_commands.h | 1 +
>  sound/soc/codecs/cros_ec_codec.c               | 9 +++++++++
>  3 files changed, 16 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/platform/chrome/cros_ec_proto.c b/drivers/platform/chrome/cros_ec_proto.c
> index 3e745e0fe092c..2c60690d7147c 100644
> --- a/drivers/platform/chrome/cros_ec_proto.c
> +++ b/drivers/platform/chrome/cros_ec_proto.c
> @@ -572,7 +572,12 @@ int cros_ec_cmd_xfer_status(struct cros_ec_device *ec_dev,
>                 return -ENOTSUPP;
>         } else if (msg->result != EC_RES_SUCCESS) {
>                 dev_dbg(ec_dev->dev, "Command result (err: %d)\n", msg->result);
> -               return -EPROTO;
> +               switch (msg->result) {
> +               case EC_RES_INVALID_PARAM:
> +                       return -EINVAL;

As we have learned, this may impact other callers of
cros_ec_cmd_xfer_status() which only accept -EPROTO as error return
value. In addition to that, the code is odd:

    if (msg->result == EC_RES_INVALID_VERSION) {
        ...
    } else if (msg->result != EC_RES_SUCCESS) {
        switch (msg->result) {
        ....
        }
    }

I really dislike the notion of changing error return values of
cros_ec_cmd_xfer_status() one by one. That can only cause ongoing
trouble with callers expecting specific error return codes (as we have
already seen).

Guenter

> +               default:
> +                       return -EPROTO;
> +               }
>         }
>
>         return ret;
> 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,
>         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 f23956cf4ed84..b5ff30b7f1aa8 100644
> --- a/sound/soc/codecs/cros_ec_codec.c
> +++ b/sound/soc/codecs/cros_ec_codec.c
> @@ -1034,6 +1034,15 @@ 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 == -EINVAL)
> +               dev_info(dev, "Missing reset command. Please update your EC firmware.\n");
> +       else if (ret)
> +               dev_err(dev, "failed to EC_CODEC_I2S_RESET: %d\n", ret);
> +
>         platform_set_drvdata(pdev, priv);
>
>         ret = devm_snd_soc_register_component(dev, &i2s_rx_component_driver,
> --
> 2.27.0.389.gc38d7665816-goog
>