linux-kernel - Re: [PATCH v12 4/5] drm/msm/dp: parser link-frequencies as property of dp

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Message-ID: <CAE-0n51G3sUbGftFr5RTsM2xwxCDW3y0N9KzAsZrSQX09_N0GA@mail.gmail.com>
Date:   Tue, 13 Dec 2022 15:18:02 -0800
From:   Stephen Boyd <swboyd@...omium.org>
To:     Kuogee Hsieh <quic_khsieh@...cinc.com>, agross@...nel.org,
        airlied@...il.com, andersson@...nel.org, daniel@...ll.ch,
        devicetree@...r.kernel.org, dianders@...omium.org,
        dmitry.baryshkov@...aro.org, dri-devel@...ts.freedesktop.org,
        konrad.dybcio@...ainline.org, krzysztof.kozlowski+dt@...aro.org,
        robdclark@...il.com, robh+dt@...nel.org, sean@...rly.run,
        vkoul@...nel.org
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 4/5] drm/msm/dp: parser link-frequencies as property
 of dp_out endpoint

Quoting Kuogee Hsieh (2022-12-13 13:44:07)
> Add capability to parser and retrieve max DP link supported rate from

to parse

> 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()
>
> Changes in v11:
> -- return 0 if(!endpoint)
>
> Changes in v12:
> -- replace khz with kbytes at dp_parser.h
>
> Signed-off-by: Kuogee Hsieh <quic_khsieh@...cinc.com>
> ---

Same parser in subject.

>  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..5549495 100644
> --- a/drivers/gpu/drm/msm/dp/dp_parser.c
> +++ b/drivers/gpu/drm/msm/dp/dp_parser.c
> @@ -91,6 +91,29 @@ 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;

'cnt' doesn't need to be initialized here.

> +
> +       endpoint = of_graph_get_endpoint_by_regs(of_node, 1, 0); /* port@1 */
> +       if (!endpoint)
> +               return 0;
> +
> +       cnt = of_property_count_u64_elems(endpoint, "link-frequencies");
> +
> +       if (cnt > 0)
> +               of_property_read_u64_index(endpoint, "link-frequencies",
> +                                               cnt - 1, &frequency);
> +       of_node_put(endpoint);
> +
> +       frequency /= 10;        /* from symbol rate to link rate */
> +       frequency /= 1000;      /* kbytes */

Use do_div(frequency, 10 * 1000)? If you want comments it could maybe be
like this:

	do_div(frequency,
	       10 * /* from symbol rate to link rate */
	       1000); /* kbytes */

> +
> +       return frequency;
> +}
> +