linux-kernel - Re: [PATCH v14 3/5] drm/msm/dp: parse data-lanes as property of dp

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Date:   Fri, 16 Dec 2022 21:46:35 +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, 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 v14 3/5] drm/msm/dp: parse data-lanes as property of
 dp_out endpoint

On 16/12/2022 21:11, Kuogee Hsieh wrote:
> Add capability to parser data-lanes as property of dp_out endpoint.
> Also retain the original capability to parser data-lanes as property
> of mdss_dp node to handle legacy case.
> 
> Changes in v6:
> -- first patch after split parser patch into two
> 
> Changes in v7:
> -- check "data-lanes" from endpoint first
> 
> Changes in v14:
> -- replace "parser" with "parse" at commit subject
> -- add matching brackets at dp_parser_misc()
> 
> Signed-off-by: Kuogee Hsieh <quic_khsieh@...cinc.com>
> Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
> ---
>   drivers/gpu/drm/msm/dp/dp_parser.c | 25 +++++++++++++++++--------
>   1 file changed, 17 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/gpu/drm/msm/dp/dp_parser.c b/drivers/gpu/drm/msm/dp/dp_parser.c
> index dd73221..d42987a 100644
> --- a/drivers/gpu/drm/msm/dp/dp_parser.c
> +++ b/drivers/gpu/drm/msm/dp/dp_parser.c
> @@ -94,16 +94,25 @@ 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;
> +	int cnt;
> +
> +	/*
> +	 * data-lanes is the property of dp_out endpoint
> +	 */
> +	cnt = drm_of_get_data_lanes_count_ep(of_node, 1, 0, 1, DP_MAX_NUM_DP_LANES);
> +	if (cnt > 0) {
> +		parser->max_dp_lanes = cnt;
> +	} else {
> +		/*
> +		 * legacy code, data-lanes is the property of mdss_dp node
> +		 */
> +		cnt = drm_of_get_data_lanes_count(of_node, 1, DP_MAX_NUM_DP_LANES);
> +		if (cnt > 0)
> +			parser->max_dp_lanes = cnt;
> +		else
> +			parser->max_dp_lanes = DP_MAX_NUM_DP_LANES; /* 4 lanes */

This bugged me for some time.

I think the following piece of code is easier to understand and handle:

cnt = drm_of_get_data_lanes_count_ep(...);

/* legacy, data-lanes property of the mdss_dp node */
if (cnt < 0)
     cnt = drm_of_get_data_lanes_count(.....);

if (cnt > 0)
     parser->max_dp_lanes = cnt;
else
     parser->max_dp_lanes = DP_MAX_NUM_DP_LANES;



>   	}
>   
> -	parser->max_dp_lanes = len;
>   	return 0;
>   }
>   

-- 
With best wishes
Dmitry