Re: [PATCH v4 1/5] mfd: cros_ec: Delay for 50ms when we see EC_CMD_REBOOT_EC

[Lee Jones <lee.jones@linaro.org>]

On Thu, 18 Sep 2014, Javier Martinez Canillas wrote:

> From: Doug Anderson <dianders@chromium.org>
> 
> If someone sends a EC_CMD_REBOOT_EC to the EC, the EC will likely be
> unresponsive for quite a while.  Add a delay to the end of the command
> to prevent random failures of future commands.
> 
> NOTES:
> * This could be optimized a bit by simply delaying the next command
>   sent, but EC_CMD_REBOOT_EC is such a rare command that the extra
>   complexity doesn't seem worth it.
> * This is a bit of an "ugly hack" since the SPI driver is effectively
>   snooping on the communication and making a lot of assumptions.  It
>   would be nice to architect in some better solution long term.
> * This same logic probably needs to be applied to the i2c driver.
> 
> Signed-off-by: Doug Anderson <dianders@chromium.org>
> Reviewed-by: Randall Spangler <rspangler@chromium.org>
> Reviewed-by: Vadim Bendebury <vbendeb@chromium.org>
> Signed-off-by: Javier Martinez Canillas <javier.martinez@collabora.co.uk>
> Acked-by: Lee Jones <lee.jones@linaro.org>
> ---
>  drivers/mfd/cros_ec_spi.c | 9 +++++++++
>  1 file changed, 9 insertions(+)

Applied, thanks.

> diff --git a/drivers/mfd/cros_ec_spi.c b/drivers/mfd/cros_ec_spi.c
> index 588c700..b396705 100644
> --- a/drivers/mfd/cros_ec_spi.c
> +++ b/drivers/mfd/cros_ec_spi.c
> @@ -65,6 +65,12 @@
>    */
>  #define EC_SPI_RECOVERY_TIME_NS	(200 * 1000)
>  
> +/*
> + * The EC is unresponsive for a time after a reboot command.  Add a
> + * simple delay to make sure that the bus stays locked.
> + */
> +#define EC_REBOOT_DELAY_MS	50
> +
>  /**
>   * struct cros_ec_spi - information about a SPI-connected EC
>   *
> @@ -318,6 +324,9 @@ static int cros_ec_cmd_xfer_spi(struct cros_ec_device *ec_dev,
>  
>  	ret = len;
>  exit:
> +	if (ec_msg->command == EC_CMD_REBOOT_EC)
> +		msleep(EC_REBOOT_DELAY_MS);
> +
>  	mutex_unlock(&ec_spi->lock);
>  	return ret;
>  }

-- 
Lee Jones
Linaro STMicroelectronics Landing Team Lead
Linaro.org │ Open source software for ARM SoCs
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