linux-kernel - Re: [PATCH] drm/msm/dp: remove limitation of link rate at 5.4G to support HBR3

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Date:   Mon, 31 Oct 2022 21:46:16 +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_abhinavk@...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] drm/msm/dp: remove limitation of link rate at 5.4G to
 support HBR3

On 31/10/2022 20:27, Kuogee Hsieh wrote:
> An HBR3-capable device shall also support TPS4. Since TPS4 feature
> had been implemented already, it is not necessary to limit link
> rate at HBR2 (5.4G). This patch remove this limitation to support
> HBR3 (8.1G) link rate.

The DP driver supports several platforms including sdm845 and can 
support, if I'm not mistaken, platforms up to msm8998/sdm630/660. Could 
you please confirm that all these SoCs have support for HBR3?

With that fact being confirmed:

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


> 
> Signed-off-by: Kuogee Hsieh <quic_khsieh@...cinc.com>
> ---
>   drivers/gpu/drm/msm/dp/dp_panel.c | 4 ----
>   1 file changed, 4 deletions(-)
> 
> diff --git a/drivers/gpu/drm/msm/dp/dp_panel.c b/drivers/gpu/drm/msm/dp/dp_panel.c
> index 5149ceb..3344f5a 100644
> --- a/drivers/gpu/drm/msm/dp/dp_panel.c
> +++ b/drivers/gpu/drm/msm/dp/dp_panel.c
> @@ -78,10 +78,6 @@ static int dp_panel_read_dpcd(struct dp_panel *dp_panel)
>   	if (link_info->num_lanes > dp_panel->max_dp_lanes)
>   		link_info->num_lanes = dp_panel->max_dp_lanes;
>   
> -	/* Limit support upto HBR2 until HBR3 support is added */
> -	if (link_info->rate >= (drm_dp_bw_code_to_link_rate(DP_LINK_BW_5_4)))
> -		link_info->rate = drm_dp_bw_code_to_link_rate(DP_LINK_BW_5_4);
> -
>   	drm_dbg_dp(panel->drm_dev, "version: %d.%d\n", major, minor);
>   	drm_dbg_dp(panel->drm_dev, "link_rate=%d\n", link_info->rate);
>   	drm_dbg_dp(panel->drm_dev, "lane_count=%d\n", link_info->num_lanes);

-- 
With best wishes
Dmitry