linux-kernel - Re: [PATCH] usb: typec: tcpm: Fix sink PDO starting index for PPS APDO selection

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Message-ID: <20180717155129.GB29933@roeck-us.net>
Date:   Tue, 17 Jul 2018 08:51:29 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Adam Thomson <Adam.Thomson.Opensource@...semi.com>
Cc:     Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
        support.opensource@...semi.com
Subject: Re: [PATCH] usb: typec: tcpm: Fix sink PDO starting index for PPS
 APDO selection

On Tue, Jul 17, 2018 at 03:36:19PM +0100, Adam Thomson wrote:
> There is a bug in the sink PDO search code when trying to select
> a PPS APDO. The current code actually sets the starting index for
> searching to whatever value 'i' is, rather than choosing index 1
> to avoid the first PDO (always 5V fixed). As a result, for sources
> which support PPS but whose PPS APDO index does not match with the
> supporting sink PPS APDO index for the platform, no valid PPS APDO
> will be found so this feature will not be permitted.
> 
> Sadly in testing, both Source and Sink capabilities matched up and
> this was missed. Code is now updated to correctly set the start
> index to 1, and testing with additional PPS capable sources show
> this to work as expected.
> 
> Signed-off-by: Adam Thomson <Adam.Thomson.Opensource@...semi.com>

Reviewed-by: Guenter Roeck <linux@...ck-us.net>

> ---
>  drivers/usb/typec/tcpm.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/usb/typec/tcpm.c b/drivers/usb/typec/tcpm.c
> index 74e0cda..4f1f421 100644
> --- a/drivers/usb/typec/tcpm.c
> +++ b/drivers/usb/typec/tcpm.c
> @@ -2238,7 +2238,7 @@ static unsigned int tcpm_pd_select_pps_apdo(struct tcpm_port *port)
>  			 * PPS APDO. Again skip the first sink PDO as this will
>  			 * always be 5V 3A.
>  			 */
> -			for (j = i; j < port->nr_snk_pdo; j++) {
> +			for (j = 1; j < port->nr_snk_pdo; j++) {
>  				pdo = port->snk_pdo[j];
>  
>  				switch (pdo_type(pdo)) {
> -- 
> 1.9.1
>