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Message-ID: <488f0db0-6fa9-8a66-f055-f2cc57470a47@quicinc.com>
Date:   Mon, 1 Aug 2022 13:18:35 -0700
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Subject: Re: [Freedreno] [PATCH v2] drm/msm/dp: delete
 DP_RECOVERED_CLOCK_OUT_EN to fix tps4
Content-Language: en-US
To:     Kuogee Hsieh <quic_khsieh@quicinc.com>, <robdclark@gmail.com>,
        <sean@poorly.run>, <swboyd@chromium.org>, <dianders@chromium.org>,
        <vkoul@kernel.org>, <daniel@ffwll.ch>, <airlied@linux.ie>,
        <agross@kernel.org>, <dmitry.baryshkov@linaro.org>,
        <bjorn.andersson@linaro.org>
CC:     <quic_sbillaka@quicinc.com>, <linux-arm-msm@vger.kernel.org>,
        <linux-kernel@vger.kernel.org>, <dri-devel@lists.freedesktop.org>,
        <quic_aravindh@quicinc.com>, <freedreno@lists.freedesktop.org>
References: <1659384830-9909-1-git-send-email-quic_khsieh@quicinc.com>
From:   Abhinav Kumar <quic_abhinavk@quicinc.com>
In-Reply-To: <1659384830-9909-1-git-send-email-quic_khsieh@quicinc.com>
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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);