Hi Tomi,
Thank you for the patch.
On Tue, Mar 26, 2019 at 12:31:38PM +0200, Tomi Valkeinen wrote:
> The driver has a loop after ending link training, where it reads the
> DPCD link status and prints an error if that status is not ok.
>
> The loop is unnecessary, as far as I can understand from DP specs, so
> let's remove it. We can also print the more specific errors to help
> debugging.
I see in tc_link_training() that the driver checks the channel EQ bits
through the TC358767 DP0_LTSTAT register. Does the chip read the link
status DPCD registers by itself through the AUX link ? If so we could
remove this check completely (unless we don't trust the TC358767 and
want to double-check). If not, where does it get the link status from ?
>
> Signed-off-by: Tomi Valkeinen <tomi.valkeinen@xxxxxx>
> ---
> drivers/gpu/drm/bridge/tc358767.c | 62 +++++++++++++++++--------------
> 1 file changed, 35 insertions(+), 27 deletions(-)
>
> diff --git a/drivers/gpu/drm/bridge/tc358767.c b/drivers/gpu/drm/bridge/tc358767.c
> index 700e161015af..220408db82f7 100644
> --- a/drivers/gpu/drm/bridge/tc358767.c
> +++ b/drivers/gpu/drm/bridge/tc358767.c
> @@ -968,34 +968,42 @@ static int tc_main_link_enable(struct tc_data *tc)
> if (ret < 0)
> goto err_dpcd_write;
>
> - /* Wait */
> - timeout = 100;
> - do {
> - udelay(1);
> - /* Read DPCD 0x202-0x207 */
> - ret = drm_dp_dpcd_read_link_status(aux, tmp + 2);
> - if (ret < 0)
> - goto err_dpcd_read;
> - } while ((--timeout) &&
> - !(drm_dp_channel_eq_ok(tmp + 2, tc->link.base.num_lanes)));
> + /* Check link status */
> + ret = drm_dp_dpcd_read_link_status(aux, tmp);
> + if (ret < 0)
> + goto err_dpcd_read;
>
> - if (timeout == 0) {
> - /* Read DPCD 0x200-0x201 */
> - ret = drm_dp_dpcd_read(aux, DP_SINK_COUNT, tmp, 2);
> - if (ret < 0)
> - goto err_dpcd_read;
> - dev_err(dev, "channel(s) EQ not ok\n");
> - dev_info(dev, "0x0200 SINK_COUNT: 0x%02x\n", tmp[0]);
> - dev_info(dev, "0x0201 DEVICE_SERVICE_IRQ_VECTOR: 0x%02x\n",
> - tmp[1]);
> - dev_info(dev, "0x0202 LANE0_1_STATUS: 0x%02x\n", tmp[2]);
> - dev_info(dev, "0x0204 LANE_ALIGN_STATUS_UPDATED: 0x%02x\n",
> - tmp[4]);
> - dev_info(dev, "0x0205 SINK_STATUS: 0x%02x\n", tmp[5]);
> - dev_info(dev, "0x0206 ADJUST_REQUEST_LANE0_1: 0x%02x\n",
> - tmp[6]);
> -
> - return -EAGAIN;
> + ret = 0;
> +
> + value = tmp[0] & DP_CHANNEL_EQ_BITS;
> +
> + if (value != DP_CHANNEL_EQ_BITS) {
> + dev_err(tc->dev, "Lane 0 failed: %x\n", value);
> + ret = -ENODEV;
> + }
> +
> + if (tc->link.base.num_lanes == 2) {
> + value = (tmp[0] >> 4) & DP_CHANNEL_EQ_BITS;
> +
> + if (value != DP_CHANNEL_EQ_BITS) {
> + dev_err(tc->dev, "Lane 1 failed: %x\n", value);
> + ret = -ENODEV;
> + }
> +
> + if (!(tmp[2] & DP_INTERLANE_ALIGN_DONE)) {
> + dev_err(tc->dev, "Interlane align failed\n");
> + ret = -ENODEV;
> + }
> + }
> +
> + if (ret) {
> + dev_err(dev, "0x0202 LANE0_1_STATUS: 0x%02x\n", tmp[0]);
> + dev_err(dev, "0x0203 LANE2_3_STATUS 0x%02x\n", tmp[1]);
> + dev_err(dev, "0x0204 LANE_ALIGN_STATUS_UPDATED: 0x%02x\n", tmp[2]);
> + dev_err(dev, "0x0205 SINK_STATUS: 0x%02x\n", tmp[3]);
> + dev_err(dev, "0x0206 ADJUST_REQUEST_LANE0_1: 0x%02x\n", tmp[4]);
> + dev_err(dev, "0x0207 ADJUST_REQUEST_LANE2_3: 0x%02x\n", tmp[5]);
> + goto err;
> }
>
> return 0;
--
Regards,
Laurent Pinchart
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