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SubjectRe: [PATCH v6 3/4] drm/msm/dp: parser link-frequencies as property of dp_out endpoint
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On 01/12/2022 01:51, 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
>
> Signed-off-by: Kuogee Hsieh <quic_khsieh@quicinc.com>
> ---
> drivers/gpu/drm/msm/dp/dp_parser.c | 16 ++++++++++++++++
> drivers/gpu/drm/msm/dp/dp_parser.h | 2 ++
> 2 files changed, 18 insertions(+)
>
> diff --git a/drivers/gpu/drm/msm/dp/dp_parser.c b/drivers/gpu/drm/msm/dp/dp_parser.c
> index b06ff60..2006341 100644
> --- a/drivers/gpu/drm/msm/dp/dp_parser.c
> +++ b/drivers/gpu/drm/msm/dp/dp_parser.c
> @@ -95,6 +95,7 @@ static int dp_parser_misc(struct dp_parser *parser)
> {
> struct device_node *of_node = parser->pdev->dev.of_node;
> struct device_node *endpoint;
> + u64 frequency;
> int cnt;
>
> /*
> @@ -103,6 +104,7 @@ static int dp_parser_misc(struct dp_parser *parser)
> cnt = drm_of_get_data_lanes_count(of_node, 1, DP_MAX_NUM_DP_LANES);
> if (cnt > 0) {
> parser->max_dp_lanes = cnt;
> + parser->max_dp_link_rate = DP_LINK_RATE_HBR2; /* 540000 khz */
> return 0;
> }
>
> @@ -116,8 +118,22 @@ static int dp_parser_misc(struct dp_parser *parser)
> parser->max_dp_lanes = DP_MAX_NUM_DP_LANES; /* 4 lanes */
> else
> parser->max_dp_lanes = cnt;
> +
> + cnt = of_property_count_u64_elems(endpoint, "link-frequencies");
> + if (cnt < 0) {
> + parser->max_dp_link_rate = DP_LINK_RATE_HBR2; /* 540000 khz */
> + } else {
> + if (cnt > DP_MAX_NUM_DP_LANES)
> + cnt = DP_MAX_NUM_DP_LANES;

Why are you comparing the number of link frequencies with the number of
lanes? You don't need the comparison at all.

> +
> + of_property_read_u64_index(endpoint, "link-frequencies",
> + cnt - 1, &frequency);

Checking of the return value?

> +
> + parser->max_dp_link_rate = (frequency / 1000); /* kbits */
> + }
> } else {
> parser->max_dp_lanes = DP_MAX_NUM_DP_LANES; /* 4 lanes */
> + parser->max_dp_link_rate = DP_LINK_RATE_HBR2; /* 540000 khz */

Instead of having all the nested if's and setting of max_dp_link rate in
several branches, please add a function that returns either a valid rate
or an error. Then you can simply check the result of that function and
set the default.

> }
>
> return 0;
> diff --git a/drivers/gpu/drm/msm/dp/dp_parser.h b/drivers/gpu/drm/msm/dp/dp_parser.h
> index 866c1a8..3ddf639 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
>
> 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

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