Re: [PATCH 2/4] usb: typec: tcpm: fix multiple times discover svids error

Heikki Krogerus
2023-03-14T09:22:24Z

On Mon, Mar 13, 2023 at 10:58:41AM +0800, Frank Wang wrote:
> PD3.0 Spec 6.4.4.3.2 say that only Responder supports 12 or more SVIDs,
> the Discover SVIDs Command Shall be executed multiple times until a
> Discover SVIDs VDO is returned ending either with a SVID value of
> 0x0000 in the last part of the last VDO or with a VDO containing two
> SVIDs with values of 0x0000.
>
> In the current implementation, if the last VDO does not find that the
> Discover SVIDs Command would be executed multiple times even if the
> Responder SVIDs are less than 12, and we found some odd dockers just
> meet this case. So fix it.
>
> Signed-off-by: Frank Wang <frank.wang@rock-chips.com>
> ---
> drivers/usb/typec/tcpm/tcpm.c | 16 +++++++++++++++-
> 1 file changed, 15 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/usb/typec/tcpm/tcpm.c b/drivers/usb/typec/tcpm/tcpm.c
> index 66de02a56f512..2962f7c261976 100644
> --- a/drivers/usb/typec/tcpm/tcpm.c
> +++ b/drivers/usb/typec/tcpm/tcpm.c
> @@ -1515,7 +1515,21 @@ static bool svdm_consume_svids(struct tcpm_port *port, const u32 *p, int cnt)
> pmdata->svids[pmdata->nsvids++] = svid;
> tcpm_log(port, "SVID %d: 0x%x", pmdata->nsvids, svid);
> }
> - return true;
> +
> + /*
> + * PD3.0 Spec 6.4.4.3.2: The SVIDs are returned 2 per VDO (see Table
> + * 6-43), and can be returned maximum 6 VDOs per response (see Figure
> + * 6-19). If the Respondersupports 12 or more SVID then the Discover
> + * SVIDs Command Shall be executed multiple times until a Discover
> + * SVIDs VDO is returned ending either with a SVID value of 0x0000 in
> + * the last part of the last VDO or with a VDO containing two SVIDs
> + * with values of 0x0000.
> + *
> + * However, some odd dockers support SVIDs less than 12 but without
> + * 0x0000 in the last VDO, so we need to break the Discover SVIDs
> + * request and return false here.
> + */
> + return cnt == 7 ? true : false;

return cnt == 7

thanks,

--
heikki