Add capability to parser and retrieve max DP link supported rate from
link-frequencies property of dp_out endpoint.

Changes in v6:
-- second patch after split parser patch into two patches

Changes in v7:
-- without checking cnt against DP_MAX_NUM_DP_LANES to retrieve link rate

Changes in v9:
-- separate parser link-frequencies out of data-lanes

Changes in v10:
-- add dp_parser_link_frequencies()

Signed-off-by: Kuogee Hsieh <quic_khsieh@quicinc.com>
---
 drivers/gpu/drm/msm/dp/dp_parser.c | 27 +++++++++++++++++++++++++++
 drivers/gpu/drm/msm/dp/dp_parser.h |  2 ++
 2 files changed, 29 insertions(+)

diff --git a/drivers/gpu/drm/msm/dp/dp_parser.c b/drivers/gpu/drm/msm/dp/dp_parser.c
index b5f7e70..9398abe 100644
--- a/drivers/gpu/drm/msm/dp/dp_parser.c
+++ b/drivers/gpu/drm/msm/dp/dp_parser.c
@@ -91,6 +91,28 @@ static int dp_parser_ctrl_res(struct dp_parser *parser)
 	return 0;
 }
 
+static u32 dp_parser_link_frequencies(struct device_node *of_node)
+{
+	struct device_node *endpoint;
+	u64 frequency = 0;
+	int cnt = 0;
+
+	endpoint = of_graph_get_endpoint_by_regs(of_node, 1, 0); /* port@1 */
+	if (endpoint)
+		cnt = of_property_count_u64_elems(endpoint, "link-frequencies");
+
+	if (cnt > 0) {
+		of_property_read_u64_index(endpoint, "link-frequencies",
+						cnt - 1, &frequency);
+		frequency /= 10;	/* from symbol rate to link rate */
+		frequency /= 1000;	/* kbits */
+	}
+
+	of_node_put(endpoint);
+
+	return (u32)frequency;
+}
+
 static int dp_parser_misc(struct dp_parser *parser)
 {
 	struct device_node *of_node = parser->pdev->dev.of_node;
@@ -113,6 +135,11 @@ static int dp_parser_misc(struct dp_parser *parser)
 			parser->max_dp_lanes = DP_MAX_NUM_DP_LANES; /* 4 lanes */
 	}
 
+	parser->max_dp_link_rate = dp_parser_link_frequencies(of_node);
+
+	if (!parser->max_dp_link_rate)
+                parser->max_dp_link_rate = DP_LINK_RATE_HBR2; /* 540000 khz */
+
 	return 0;
 }
 
diff --git a/drivers/gpu/drm/msm/dp/dp_parser.h b/drivers/gpu/drm/msm/dp/dp_parser.h
index 866c1a8..6b10c3e 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_RATE_HBR2	540000 /* khz */
 
 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);
-- 
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project

On 07/12/2022 18:57, Kuogee Hsieh wrote:
> Add capability to parser and retrieve max DP link supported rate from
> link-frequencies property of dp_out endpoint.
> 
> Changes in v6:
> -- second patch after split parser patch into two patches
> 
> Changes in v7:
> -- without checking cnt against DP_MAX_NUM_DP_LANES to retrieve link rate
> 
> Changes in v9:
> -- separate parser link-frequencies out of data-lanes
> 
> Changes in v10:
> -- add dp_parser_link_frequencies()
> 
> Signed-off-by: Kuogee Hsieh <quic_khsieh@quicinc.com>
> ---
>   drivers/gpu/drm/msm/dp/dp_parser.c | 27 +++++++++++++++++++++++++++
>   drivers/gpu/drm/msm/dp/dp_parser.h |  2 ++
>   2 files changed, 29 insertions(+)
> 
> diff --git a/drivers/gpu/drm/msm/dp/dp_parser.c b/drivers/gpu/drm/msm/dp/dp_parser.c
> index b5f7e70..9398abe 100644
> --- a/drivers/gpu/drm/msm/dp/dp_parser.c
> +++ b/drivers/gpu/drm/msm/dp/dp_parser.c
> @@ -91,6 +91,28 @@ static int dp_parser_ctrl_res(struct dp_parser *parser)
>   	return 0;
>   }
>   
> +static u32 dp_parser_link_frequencies(struct device_node *of_node)
> +{
> +	struct device_node *endpoint;
> +	u64 frequency = 0;
> +	int cnt = 0;
> +
> +	endpoint = of_graph_get_endpoint_by_regs(of_node, 1, 0); /* port@1 */

if (!endpoint)
   return -ENODEV; (or 0, as you have u32)

It's much easier IMO.

> +	if (endpoint)
> +		cnt = of_property_count_u64_elems(endpoint, "link-frequencies");
> +
> +	if (cnt > 0) {
> +		of_property_read_u64_index(endpoint, "link-frequencies",
> +						cnt - 1, &frequency);
> +		frequency /= 10;	/* from symbol rate to link rate */
> +		frequency /= 1000;	/* kbits */

kbytes?

> +	}
> +
> +	of_node_put(endpoint);

Even easier:

cnt = of_property_count(...);
if (cnt > 0)
     of_property_read_u64_index(...);
of_node_put(endpoint);

frequency /= 10;
frequency /= 1000;

return frequency;

> +
> +	return (u32)frequency;
> +}
> +
>   static int dp_parser_misc(struct dp_parser *parser)
>   {
>   	struct device_node *of_node = parser->pdev->dev.of_node;
> @@ -113,6 +135,11 @@ static int dp_parser_misc(struct dp_parser *parser)
>   			parser->max_dp_lanes = DP_MAX_NUM_DP_LANES; /* 4 lanes */
>   	}
>   
> +	parser->max_dp_link_rate = dp_parser_link_frequencies(of_node);
> +

Drop the empty line please. The if checks the result of the previous 
assignment. It's easier to comprehend if they visually belong to the 
same code block.

> +	if (!parser->max_dp_link_rate)
> +                parser->max_dp_link_rate = DP_LINK_RATE_HBR2; /* 540000 khz */
> +
>   	return 0;
>   }
>   
> diff --git a/drivers/gpu/drm/msm/dp/dp_parser.h b/drivers/gpu/drm/msm/dp/dp_parser.h
> index 866c1a8..6b10c3e 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_RATE_HBR2	540000 /* khz */
>   
>   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