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Message-ID: <d17a595c-9561-1efa-b72e-15c535ef31eb@linaro.org>
Date: Wed, 7 Dec 2022 22:13:23 +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, airlied@...ux.ie,
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 v10 4/5] drm/msm/dp: parser link-frequencies as property
of dp_out endpoint
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@...cinc.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
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