linux-kernel - Re: [PATCH v2] drm/msm/dp: delete DP_RECOVERED_CLOCK_OUT

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Message-ID: <bdf6abfe-89e3-80bb-6c5e-fcea713814e9@linaro.org>
Date:   Tue, 2 Aug 2022 09:43:40 +0300
From:   Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To:     Kuogee Hsieh <quic_khsieh@...cinc.com>, robdclark@...il.com,
        sean@...rly.run, swboyd@...omium.org, dianders@...omium.org,
        vkoul@...nel.org, daniel@...ll.ch, airlied@...ux.ie,
        agross@...nel.org, bjorn.andersson@...aro.org
Cc:     quic_aravindh@...cinc.com, quic_sbillaka@...cinc.com,
        freedreno@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
        linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] drm/msm/dp: delete DP_RECOVERED_CLOCK_OUT_EN to fix
 tps4

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@...aro.org>

> 
> Changes in v2:
> -- fix Fixes tag
> 
> Fixes: c943b4948b58 ("drm/msm/dp: add displayPort driver support")
> Signed-off-by: Kuogee Hsieh <quic_khsieh@...cinc.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