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    Subject[PATCH 4.19 003/106] drm/bridge: tc358767: Increase AUX transfer length limit
    Date
    From: Andrey Smirnov <andrew.smirnov@gmail.com>

    [ Upstream commit e0655feaec62d5139b6b13a7b1bbb1ab8f1c2d83 ]

    According to the datasheet tc358767 can transfer up to 16 bytes via
    its AUX channel, so the artificial limit of 8 appears 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@gmail.com>
    Reviewed-by: Andrzej Hajda <a.hajda@samsung.com>
    Reviewed-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
    Cc: Andrzej Hajda <a.hajda@samsung.com>
    Cc: Laurent Pinchart <Laurent.pinchart@ideasonboard.com>
    Cc: Tomi Valkeinen <tomi.valkeinen@ti.com>
    Cc: Andrey Gusakov <andrey.gusakov@cogentembedded.com>
    Cc: Philipp Zabel <p.zabel@pengutronix.de>
    Cc: Cory Tusar <cory.tusar@zii.aero>
    Cc: Chris Healy <cphealy@gmail.com>
    Cc: Lucas Stach <l.stach@pengutronix.de>
    Cc: dri-devel@lists.freedesktop.org
    Cc: linux-kernel@vger.kernel.org
    Signed-off-by: Andrzej Hajda <a.hajda@samsung.com>
    Link: https://patchwork.freedesktop.org/patch/msgid/20190619052716.16831-9-andrew.smirnov@gmail.com
    Signed-off-by: Sasha Levin <sashal@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 aaca5248da070..d728b6cf61096 100644
    --- a/drivers/gpu/drm/bridge/tc358767.c
    +++ b/drivers/gpu/drm/bridge/tc358767.c
    @@ -302,7 +302,7 @@ 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;
    u8 *buf = msg->buffer;
    u32 tmp = 0;
    --
    2.20.1


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