linux-kernel - Re: [PATCH v12 5/5] drm/msm/dp: add support of max dp link rate

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Message-ID: <8FEED6F1-4F23-4B17-AD4C-8145CDE8C47B@linaro.org>
Date:   Wed, 14 Dec 2022 00:06:21 +0200
From:   Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To:     Kuogee Hsieh <quic_khsieh@...cinc.com>,
        dri-devel@...ts.freedesktop.org, robdclark@...il.com,
        sean@...rly.run, swboyd@...omium.org, dianders@...omium.org,
        vkoul@...nel.org, daniel@...ll.ch, agross@...nel.org,
        andersson@...nel.org, konrad.dybcio@...ainline.org,
        robh+dt@...nel.org, krzysztof.kozlowski+dt@...aro.org,
        devicetree@...r.kernel.org, airlied@...il.com
CC:     quic_abhinavk@...cinc.com, quic_sbillaka@...cinc.com,
        freedreno@...ts.freedesktop.org, linux-arm-msm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v12 5/5] drm/msm/dp: add support of max dp link rate



On 13 December 2022 23:44:08 EET, Kuogee Hsieh <quic_khsieh@...cinc.com> wrote:
>By default, HBR2 (5.4G) is the max link link be supported. This patch uses the
>actual limit specified by DT and removes the artificial limitation to 5.4 Gbps.
>Supporting HBR3 is a consequence of that.
>
>Changes in v2:
>-- add max link rate from dtsi
>
>Changes in v3:
>-- parser max_data_lanes and max_dp_link_rate from dp_out endpoint
>
>Changes in v4:
>-- delete unnecessary pr_err
>
>Changes in v5:
>-- split parser function into different patch
>
>Changes in v9:
>-- revised commit test
>
>Signed-off-by: Kuogee Hsieh <quic_khsieh@...cinc.com>
>Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
>---
> drivers/gpu/drm/msm/dp/dp_display.c | 4 ++++
> drivers/gpu/drm/msm/dp/dp_panel.c   | 7 ++++---
> drivers/gpu/drm/msm/dp/dp_panel.h   | 1 +
> 3 files changed, 9 insertions(+), 3 deletions(-)
>
>diff --git a/drivers/gpu/drm/msm/dp/dp_display.c b/drivers/gpu/drm/msm/dp/dp_display.c
>index bfd0aef..edee550 100644
>--- a/drivers/gpu/drm/msm/dp/dp_display.c
>+++ b/drivers/gpu/drm/msm/dp/dp_display.c
>@@ -390,6 +390,10 @@ static int dp_display_process_hpd_high(struct dp_display_private *dp)
> 	struct edid *edid;
> 
> 	dp->panel->max_dp_lanes = dp->parser->max_dp_lanes;
>+	dp->panel->max_dp_link_rate = dp->parser->max_dp_link_rate;
>+
>+	drm_dbg_dp(dp->drm_dev, "max_lanes=%d max_link_rate=%d\n",
>+		dp->panel->max_dp_lanes, dp->panel->max_dp_link_rate);
> 
> 	rc = dp_panel_read_sink_caps(dp->panel, dp->dp_display.connector);
> 	if (rc)
>diff --git a/drivers/gpu/drm/msm/dp/dp_panel.c b/drivers/gpu/drm/msm/dp/dp_panel.c
>index 5149ceb..933fa9c 100644
>--- a/drivers/gpu/drm/msm/dp/dp_panel.c
>+++ b/drivers/gpu/drm/msm/dp/dp_panel.c
>@@ -75,12 +75,13 @@ static int dp_panel_read_dpcd(struct dp_panel *dp_panel)
> 	link_info->rate = drm_dp_bw_code_to_link_rate(dpcd[DP_MAX_LINK_RATE]);
> 	link_info->num_lanes = dpcd[DP_MAX_LANE_COUNT] & DP_MAX_LANE_COUNT_MASK;
> 
>+	/* Limit data lanes from data-lanes of endpoint properity of dtsi */

Nit: property. And below too.

> 	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);
>+	/* Limit link rate from link-frequencies of endpoint properity of dtsi */
>+	if (link_info->rate > dp_panel->max_dp_link_rate)
>+		link_info->rate = dp_panel->max_dp_link_rate;
> 
> 	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);
>diff --git a/drivers/gpu/drm/msm/dp/dp_panel.h b/drivers/gpu/drm/msm/dp/dp_panel.h
>index d861197a..f04d021 100644
>--- a/drivers/gpu/drm/msm/dp/dp_panel.h
>+++ b/drivers/gpu/drm/msm/dp/dp_panel.h
>@@ -50,6 +50,7 @@ struct dp_panel {
> 
> 	u32 vic;
> 	u32 max_dp_lanes;
>+	u32 max_dp_link_rate;
> 
> 	u32 max_bw_code;
> };

-- 
With best wishes
Dmitry