linux-kernel - Re: [PATCH v3 08/15] drm/bridge: tc358767: Increase AUX transfer length limit

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Date:   Thu, 6 Jun 2019 13:10:12 +0200
From:   Andrzej Hajda <a.hajda@...sung.com>
To:     Andrey Smirnov <andrew.smirnov@...il.com>,
        dri-devel@...ts.freedesktop.org
Cc:     Archit Taneja <architt@...eaurora.org>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        Tomi Valkeinen <tomi.valkeinen@...com>,
        Andrey Gusakov <andrey.gusakov@...entembedded.com>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Cory Tusar <cory.tusar@....aero>,
        Chris Healy <cphealy@...il.com>,
        Lucas Stach <l.stach@...gutronix.de>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 08/15] drm/bridge: tc358767: Increase AUX transfer
 length limit

On 05.06.2019 09:05, Andrey Smirnov wrote:
> According to the datasheet tc358767 can transfer up to 16 bytes via
> its AUX channel, so the artificial limit of 8 apperas to be too
> low. However only up to 15-bytes seem to be actually supported and
> trying to use 16-byte transfers results in transfers failing
> sporadically (with bogus status in case of I2C transfers), so limit it
> to 15.
>
> Signed-off-by: Andrey Smirnov <andrew.smirnov@...il.com>
> Cc: Archit Taneja <architt@...eaurora.org>


Please remove Archit's mail (from all patches), it is no longer valid.


Reviewed-by: Andrzej Hajda <a.hajda@...sung.com>

 --
Regards
Andrzej


> Cc: Andrzej Hajda <a.hajda@...sung.com>
> Cc: Laurent Pinchart <Laurent.pinchart@...asonboard.com>
> Cc: Tomi Valkeinen <tomi.valkeinen@...com>
> Cc: Andrey Gusakov <andrey.gusakov@...entembedded.com>
> Cc: Philipp Zabel <p.zabel@...gutronix.de>
> Cc: Cory Tusar <cory.tusar@....aero>
> Cc: Chris Healy <cphealy@...il.com>
> Cc: Lucas Stach <l.stach@...gutronix.de>
> Cc: dri-devel@...ts.freedesktop.org
> Cc: linux-kernel@...r.kernel.org
> ---
>  drivers/gpu/drm/bridge/tc358767.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/bridge/tc358767.c b/drivers/gpu/drm/bridge/tc358767.c
> index 260fbcd0271e..0125e2f7e076 100644
> --- a/drivers/gpu/drm/bridge/tc358767.c
> +++ b/drivers/gpu/drm/bridge/tc358767.c
> @@ -374,7 +374,7 @@ static ssize_t tc_aux_transfer(struct drm_dp_aux *aux,
>  			       struct drm_dp_aux_msg *msg)
>  {
>  	struct tc_data *tc = aux_to_tc(aux);
> -	size_t size = min_t(size_t, 8, msg->size);
> +	size_t size = min_t(size_t, DP_AUX_MAX_PAYLOAD_BYTES - 1, msg->size);
>  	u8 request = msg->request & ~DP_AUX_I2C_MOT;
>  	int ret;
>