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SubjectRe: [PATCH 7/7] drm/msm/dp: retrain link when loss of symbol lock detected
On 2021-07-08 00:21, Stephen Boyd wrote:
> Quoting Kuogee Hsieh (2021-07-06 10:20:20)
>> Main link symbol locked is achieved at end of link training 2. Some
>> dongle main link symbol may become unlocked again if host did not end
>> link training soon enough after completion of link training 2. Host
>> have to re train main link if loss of symbol lock detected before
>> end link training so that the coming video stream can be transmitted
>> to sink properly.
>>
>> Signed-off-by: Kuogee Hsieh <khsieh@codeaurora.org>
>
> I guess this is a fix for the original driver, so it should be tagged
> with Fixes appropriately.
Actually, this is fix on patch #6 : drm/msm/dp: do not end dp link
training until video is ready
Should i merge patch #6 and #7 together?
Or can you suggest what should I do?
>
>> ---
>> drivers/gpu/drm/msm/dp/dp_ctrl.c | 34
>> ++++++++++++++++++++++++++++++++++
>> 1 file changed, 34 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/msm/dp/dp_ctrl.c
>> b/drivers/gpu/drm/msm/dp/dp_ctrl.c
>> index 0cb01a9..e616ab2 100644
>> --- a/drivers/gpu/drm/msm/dp/dp_ctrl.c
>> +++ b/drivers/gpu/drm/msm/dp/dp_ctrl.c
>> @@ -1661,6 +1661,25 @@ static bool dp_ctrl_any_lane_cr_lose(struct
>> dp_ctrl_private *ctrl,
>> return false;
>> }
>>
>> +static bool dp_ctrl_loss_symbol_lock(struct dp_ctrl_private *ctrl)
>> +{
>> + u8 link_status[6];
>
> Can we use link_status[DP_LINK_STATUS_SIZE] instead?
>
>> + u8 status;
>> + int i;
>> + int lane = ctrl->link->link_params.num_lanes;
>
> s/lane/num_lanes/
>
> would make the code easier to read
>
>> +
>> + dp_ctrl_read_link_status(ctrl, link_status);
>> +
>> + for (i = 0; i < lane; i++) {
>> + status = link_status[i / 2];
>> + status >>= ((i % 2) * 4);
>> + if (!(status & DP_LANE_SYMBOL_LOCKED))
>> + return true;
>> + }
>> +
>> + return false;
>> +}
>> +
>> int dp_ctrl_on_link(struct dp_ctrl *dp_ctrl)
>> {
>> int rc = 0;
>> @@ -1777,6 +1796,17 @@ int dp_ctrl_on_link(struct dp_ctrl *dp_ctrl)
>> return rc;
>> }
>>
>> +static int dp_ctrl_link_retrain(struct dp_ctrl_private *ctrl)
>> +{
>> + int ret = 0;
>
> Please drop init of ret.
>
>> + u8 cr_status[2];
>> + int training_step = DP_TRAINING_NONE;
>> +
>> + ret = dp_ctrl_setup_main_link(ctrl, cr_status,
>> &training_step);
>
> as it is assigned here.
>
>> +
>> + return ret;
>
> And indeed, it could be 'return dp_ctrl_setup_main_link()' instead.
>
>> +}
>> +
>> int dp_ctrl_on_stream(struct dp_ctrl *dp_ctrl)
>> {
>> int ret = 0;
>> @@ -1802,6 +1832,10 @@ int dp_ctrl_on_stream(struct dp_ctrl *dp_ctrl)
>> }
>> }
>>
>> + /* if loss symbol lock happen, then retaining the link */
>
> retain or retrain? The comment seems to be saying what the code says
> "if
> loss retrain", so the comment is not very useful.
>
>> + if (dp_ctrl_loss_symbol_lock(ctrl))
>> + dp_ctrl_link_retrain(ctrl);
>> +
>> /* stop txing train pattern to end link training */
>> dp_ctrl_clear_training_pattern(ctrl);
>>

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