Re: [PATCH] usb: typec: mux: intel_pmc_mux: Add retry logic to a PMC command

[Heikki Krogerus]

On Mon, Mar 28, 2022 at 04:21:37PM +0530, tanveer1.alam@xxxxxxxxx wrote:
> From: Tanveer Alam <tanveer1.alam@xxxxxxxxx>
> 
> There are few scenerio when PMC reports 'busy condition' and command
> fail.
> 
> If PMC receives a high priority command while servicing a low priority
> command then it discards the low priority command and start servicing
> the high priority command. The lower priority command fail and driver
> returns error. If the same command resend to the PMC then PMC latches
> the command and service it accordingly.
> 
> Thus adds the retry logic for the PMC command.
> 
> Signed-off-by: Tanveer Alam <tanveer1.alam@xxxxxxxxx>

Reviewed-by: Heikki Krogerus <heikki.krogerus@xxxxxxxxxxxxxxx>

> ---
>  drivers/usb/typec/mux/intel_pmc_mux.c | 21 +++++++++++++++++++--
>  1 file changed, 19 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/usb/typec/mux/intel_pmc_mux.c b/drivers/usb/typec/mux/intel_pmc_mux.c
> index 2cdd22130834..da6b381ddf00 100644
> --- a/drivers/usb/typec/mux/intel_pmc_mux.c
> +++ b/drivers/usb/typec/mux/intel_pmc_mux.c
> @@ -173,7 +173,7 @@ static int hsl_orientation(struct pmc_usb_port *port)
>  	return port->orientation - 1;
>  }
>  
> -static int pmc_usb_command(struct pmc_usb_port *port, u8 *msg, u32 len)
> +static int pmc_usb_send_command(struct intel_scu_ipc_dev *ipc, u8 *msg, u32 len)
>  {
>  	u8 response[4];
>  	u8 status_res;
> @@ -184,7 +184,7 @@ static int pmc_usb_command(struct pmc_usb_port *port, u8 *msg, u32 len)
>  	 * Status can be checked from the response message if the
>  	 * function intel_scu_ipc_dev_command succeeds.
>  	 */
> -	ret = intel_scu_ipc_dev_command(port->pmc->ipc, PMC_USBC_CMD, 0, msg,
> +	ret = intel_scu_ipc_dev_command(ipc, PMC_USBC_CMD, 0, msg,
>  					len, response, sizeof(response));
>  
>  	if (ret)
> @@ -203,6 +203,23 @@ static int pmc_usb_command(struct pmc_usb_port *port, u8 *msg, u32 len)
>  	return 0;
>  }
>  
> +static int pmc_usb_command(struct pmc_usb_port *port, u8 *msg, u32 len)
> +{
> +	int retry_count = 3;
> +	int ret;
> +
> +	/*
> +	 * If PMC is busy then retry the command once again
> +	 */
> +	while (retry_count--) {
> +		ret = pmc_usb_send_command(port->pmc->ipc, msg, len);
> +		if (ret != -EBUSY)
> +			break;
> +	}
> +
> +	return ret;
> +}
> +
>  static int
>  pmc_usb_mux_dp_hpd(struct pmc_usb_port *port, struct typec_displayport_data *dp)
>  {

thanks,

-- 
heikki