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

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Date:   Tue, 14 Mar 2023 11:22:13 +0200
From:   Heikki Krogerus <heikki.krogerus@...ux.intel.com>
To:     Frank Wang <frank.wang@...k-chips.com>
Cc:     linux@...ck-us.net, gregkh@...uxfoundation.org, heiko@...ech.de,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-rockchip@...ts.infradead.org, huangtao@...k-chips.com,
        william.wu@...k-chips.com, jianwei.zheng@...k-chips.com,
        yubing.zhang@...k-chips.com, wmc@...k-chips.com
Subject: Re: [PATCH 2/4] usb: typec: tcpm: fix multiple times discover svids
 error

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@...k-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