[PATCH v2] drm/msm/dp: delete DP_RECOVERED_CLOCK_OUT_EN to fix tps4

[PATCH v2] drm/msm/dp: delete DP_RECOVERED_CLOCK_OUT_EN to fix tps4

[Kuogee Hsieh]

Data Symbols scrambled is required for tps4 at link training 2.
Therefore SCRAMBLING_DISABLE bit should not be set for tps4 to
work.
RECOVERED_CLOCK_OUT_EN is for enable simple EYE test for jitter
measurement with minimal equipment for embedded applications purpose
and is not required to be set during normal operation.
Current implementation always have RECOVERED_CLOCK_OUT_EN bit set
which cause SCRAMBLING_DISABLE bit wrongly set at tps4 which prevent
tps4 from working.
This patch delete setting RECOVERED_CLOCK_OUT_EN to fix SCRAMBLING_DISABLE
be wrongly set at tps4.

Changes in v2:
-- fix Fixes tag

Fixes: c943b4948b58 ("drm/msm/dp: add displayPort driver support")
Signed-off-by: Kuogee Hsieh <quic_khsieh@quicinc.com>
---
 drivers/gpu/drm/msm/dp/dp_ctrl.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/msm/dp/dp_ctrl.c b/drivers/gpu/drm/msm/dp/dp_ctrl.c
index ab6aa13..013ca02 100644
--- a/drivers/gpu/drm/msm/dp/dp_ctrl.c
+++ b/drivers/gpu/drm/msm/dp/dp_ctrl.c
@@ -1214,7 +1214,7 @@ static int dp_ctrl_link_train_2(struct dp_ctrl_private *ctrl,
 	if (ret)
 		return ret;
 
-	dp_ctrl_train_pattern_set(ctrl, pattern | DP_RECOVERED_CLOCK_OUT_EN);
+	dp_ctrl_train_pattern_set(ctrl, pattern);
 
 	for (tries = 0; tries <= maximum_retries; tries++) {
 		drm_dp_link_train_channel_eq_delay(ctrl->aux, ctrl->panel->dpcd);
-- 
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project

Re: [Freedreno] [PATCH v2] drm/msm/dp: delete DP_RECOVERED_CLOCK_OUT_EN to fix tps4

[Abhinav Kumar]

On 8/1/2022 1:13 PM, Kuogee Hsieh wrote:
> Data Symbols scrambled is required for tps4 at link training 2.
> Therefore SCRAMBLING_DISABLE bit should not be set for tps4 to
> work.
> RECOVERED_CLOCK_OUT_EN is for enable simple EYE test for jitter
> measurement with minimal equipment for embedded applications purpose
> and is not required to be set during normal operation.
> Current implementation always have RECOVERED_CLOCK_OUT_EN bit set
> which cause SCRAMBLING_DISABLE bit wrongly set at tps4 which prevent
> tps4 from working.
> This patch delete setting RECOVERED_CLOCK_OUT_EN to fix SCRAMBLING_DISABLE
> be wrongly set at tps4.
> 
> Changes in v2:
> -- fix Fixes tag
> 
> Fixes: c943b4948b58 ("drm/msm/dp: add displayPort driver support")
> Signed-off-by: Kuogee Hsieh <quic_khsieh@quicinc.com>

This is a good catch !

Reviewed-by: Abhinav Kumar <quic_abhinavk@quicinc.com>

> ---
>   drivers/gpu/drm/msm/dp/dp_ctrl.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/msm/dp/dp_ctrl.c b/drivers/gpu/drm/msm/dp/dp_ctrl.c
> index ab6aa13..013ca02 100644
> --- a/drivers/gpu/drm/msm/dp/dp_ctrl.c
> +++ b/drivers/gpu/drm/msm/dp/dp_ctrl.c
> @@ -1214,7 +1214,7 @@ static int dp_ctrl_link_train_2(struct dp_ctrl_private *ctrl,
>   	if (ret)
>   		return ret;
>   
> -	dp_ctrl_train_pattern_set(ctrl, pattern | DP_RECOVERED_CLOCK_OUT_EN);
> +	dp_ctrl_train_pattern_set(ctrl, pattern);
>   
>   	for (tries = 0; tries <= maximum_retries; tries++) {
>   		drm_dp_link_train_channel_eq_delay(ctrl->aux, ctrl->panel->dpcd);

Re: [PATCH v2] drm/msm/dp: delete DP_RECOVERED_CLOCK_OUT_EN to fix tps4

[Stephen Boyd]

Quoting Kuogee Hsieh (2022-08-01 13:13:50)
> Data Symbols scrambled is required for tps4 at link training 2.
> Therefore SCRAMBLING_DISABLE bit should not be set for tps4 to
> work.
> RECOVERED_CLOCK_OUT_EN is for enable simple EYE test for jitter
> measurement with minimal equipment for embedded applications purpose
> and is not required to be set during normal operation.
> Current implementation always have RECOVERED_CLOCK_OUT_EN bit set
> which cause SCRAMBLING_DISABLE bit wrongly set at tps4 which prevent
> tps4 from working.
> This patch delete setting RECOVERED_CLOCK_OUT_EN to fix SCRAMBLING_DISABLE
> be wrongly set at tps4.
>
> Changes in v2:
> -- fix Fixes tag
>
> Fixes: c943b4948b58 ("drm/msm/dp: add displayPort driver support")
> Signed-off-by: Kuogee Hsieh <quic_khsieh@quicinc.com>
> ---

Reviewed-by: Stephen Boyd <swboyd@chromium.org>

Re: [PATCH v2] drm/msm/dp: delete DP_RECOVERED_CLOCK_OUT_EN to fix tps4

[Dmitry Baryshkov]

On 01/08/2022 23:13, Kuogee Hsieh wrote:
> Data Symbols scrambled is required for tps4 at link training 2.
> Therefore SCRAMBLING_DISABLE bit should not be set for tps4 to
> work.
> RECOVERED_CLOCK_OUT_EN is for enable simple EYE test for jitter
> measurement with minimal equipment for embedded applications purpose
> and is not required to be set during normal operation.
> Current implementation always have RECOVERED_CLOCK_OUT_EN bit set
> which cause SCRAMBLING_DISABLE bit wrongly set at tps4 which prevent
> tps4 from working.
> This patch delete setting RECOVERED_CLOCK_OUT_EN to fix SCRAMBLING_DISABLE
> be wrongly set at tps4.

Minor nits, more likely concerning feature patches:
- Please insert blank lines between paragraphs, it makes commit message 
easier to read. And please add no extra line breaks if you do not intent 
to end the paragraph here.

- "This patch" is generally the frowned upon phrase (see 
Documentation/process/submitting-patches.rst)

Nevertheless:

Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>

> 
> Changes in v2:
> -- fix Fixes tag
> 
> Fixes: c943b4948b58 ("drm/msm/dp: add displayPort driver support")
> Signed-off-by: Kuogee Hsieh <quic_khsieh@quicinc.com>
> ---
>   drivers/gpu/drm/msm/dp/dp_ctrl.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/msm/dp/dp_ctrl.c b/drivers/gpu/drm/msm/dp/dp_ctrl.c
> index ab6aa13..013ca02 100644
> --- a/drivers/gpu/drm/msm/dp/dp_ctrl.c
> +++ b/drivers/gpu/drm/msm/dp/dp_ctrl.c
> @@ -1214,7 +1214,7 @@ static int dp_ctrl_link_train_2(struct dp_ctrl_private *ctrl,
>   	if (ret)
>   		return ret;
>   
> -	dp_ctrl_train_pattern_set(ctrl, pattern | DP_RECOVERED_CLOCK_OUT_EN);
> +	dp_ctrl_train_pattern_set(ctrl, pattern);
>   
>   	for (tries = 0; tries <= maximum_retries; tries++) {
>   		drm_dp_link_train_channel_eq_delay(ctrl->aux, ctrl->panel->dpcd);


-- 
With best wishes
Dmitry