Re: [PATCH v3 2/2] drm/msm/dp: add support of max dp link rate

From: Dmitry Baryshkov
Date: Fri Nov 18 2022 - 06:04:51 EST

On 18/11/2022 01:49, Kuogee Hsieh wrote:
dp_out endpoint contains both data-lanes and link-frequencies properties.
This patch parser dp_out endpoint properties and acquire dp_max_lanes and
dp_max_link_rate from respective property. Finally, comparing them against
both data lane and link rate read back from sink to ensure both data lane
and link rate are supported by platform.
In the case there is no data-lanes or link-frequencies property defined at
dp_out endpoint, the default value are 4 data lanes with 5.4 Ghz link rate.

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

Signed-off-by: Kuogee Hsieh <quic_khsieh@xxxxxxxxxxx>
---
arch/arm64/boot/dts/qcom/sc7280.dtsi | 1 +

Should not be a part of this patch.

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 +
drivers/gpu/drm/msm/dp/dp_parser.c | 30 ++++++++++++++++++++++--------
drivers/gpu/drm/msm/dp/dp_parser.h | 2 ++
6 files changed, 34 insertions(+), 11 deletions(-)

diff --git a/arch/arm64/boot/dts/qcom/sc7280.dtsi b/arch/arm64/boot/dts/qcom/sc7280.dtsi
index 4afe53b..d456e76 100644
--- a/arch/arm64/boot/dts/qcom/sc7280.dtsi
+++ b/arch/arm64/boot/dts/qcom/sc7280.dtsi
@@ -3897,6 +3897,7 @@
reg = <0>;
dp_in: endpoint {
remote-endpoint = <&dpu_intf0_out>;
+ data-lanes = <0 1 2 3>;
};
};
};
diff --git a/drivers/gpu/drm/msm/dp/dp_display.c b/drivers/gpu/drm/msm/dp/dp_display.c
index 29c9845..4fe2092 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 */
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;
};
diff --git a/drivers/gpu/drm/msm/dp/dp_parser.c b/drivers/gpu/drm/msm/dp/dp_parser.c
index dd73221..667981e 100644
--- a/drivers/gpu/drm/msm/dp/dp_parser.c
+++ b/drivers/gpu/drm/msm/dp/dp_parser.c
@@ -94,16 +94,30 @@ static int dp_parser_ctrl_res(struct dp_parser *parser)
static int dp_parser_misc(struct dp_parser *parser)
{
struct device_node *of_node = parser->pdev->dev.of_node;
- int len;
-
- len = drm_of_get_data_lanes_count(of_node, 1, DP_MAX_NUM_DP_LANES);
- if (len < 0) {
- DRM_WARN("Invalid property \"data-lanes\", default max DP lanes = %d\n",
- DP_MAX_NUM_DP_LANES);
- len = DP_MAX_NUM_DP_LANES;
+ struct device_node *endpoint;
+ int cnt;
+ u32 frequence = 0;
+
+ endpoint = of_graph_get_endpoint_by_regs(of_node, 1, 0);
+
+ if (endpoint) {
+ cnt = of_property_count_u32_elems(endpoint, "data-lanes");
+ if (cnt < 0)
+ parser->max_dp_lanes = DP_MAX_NUM_DP_LANES; /* 4 lanes */
+ else
+ parser->max_dp_lanes = cnt;

This should be a separate patch. And now what, drm_of_get_data_lanes_count() can be used here too. Why are you dropping the generic function for the sake of your custom implementatoin.

+
+ cnt = of_property_count_u32_elems(endpoint, "link-frequencies");
+ if (cnt < 0) {
+ parser->max_dp_link_rate = DP_LINK_FREQUENCY_HBR2; /* 54000 khz */
+ } else {
+ of_property_read_u32_array(endpoint, "link-frequencies", &frequence, 1);

link-frequencies is u64 array.

+ parser->max_dp_link_rate = frequence;
+ }
}
- parser->max_dp_lanes = len;
+ pr_err("%s: kuogee, lane=%d frequency=%d\n", __func__, parser->max_dp_lanes, parser->max_dp_link_rate);
+

Leftover?

return 0;
}
diff --git a/drivers/gpu/drm/msm/dp/dp_parser.h b/drivers/gpu/drm/msm/dp/dp_parser.h
index 866c1a8..76ddb751 100644
--- a/drivers/gpu/drm/msm/dp/dp_parser.h
+++ b/drivers/gpu/drm/msm/dp/dp_parser.h
@@ -15,6 +15,7 @@
#define DP_LABEL "MDSS DP DISPLAY"
#define DP_MAX_PIXEL_CLK_KHZ 675000
#define DP_MAX_NUM_DP_LANES 4
+#define DP_LINK_FREQUENCY_HBR2 540000
enum dp_pm_type {
DP_CORE_PM,
@@ -119,6 +120,7 @@ struct dp_parser {
struct dp_io io;
struct dp_display_data disp_data;
u32 max_dp_lanes;
+ u32 max_dp_link_rate;
struct drm_bridge *next_bridge;
int (*parse)(struct dp_parser *parser);

--
With best wishes
Dmitry