linux-kernel - Re: [PATCH v3 3/7] drm/msm/mdp4: register the LVDS PLL as a clock provider

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Message-ID: <029f3bfb-a031-4dfe-a2b4-bc41a0da7772@quicinc.com>
Date: Wed, 23 Apr 2025 15:54:13 -0700
From: Abhinav Kumar <quic_abhinavk@...cinc.com>
To: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        Rob Clark
	<robdclark@...il.com>, Sean Paul <sean@...rly.run>,
        Marijn Suijten
	<marijn.suijten@...ainline.org>,
        Maarten Lankhorst
	<maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <mripard@...nel.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
        Rob Herring <robh@...nel.org>,
        "Krzysztof
 Kozlowski" <krzk+dt@...nel.org>,
        Conor Dooley <conor+dt@...nel.org>,
        "Bjorn
 Andersson" <andersson@...nel.org>,
        Konrad Dybcio <konradybcio@...nel.org>
CC: <linux-arm-msm@...r.kernel.org>, <dri-devel@...ts.freedesktop.org>,
        <freedreno@...ts.freedesktop.org>, <devicetree@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>,
        Konrad Dybcio
	<konrad.dybcio@....qualcomm.com>
Subject: Re: [PATCH v3 3/7] drm/msm/mdp4: register the LVDS PLL as a clock
 provider



On 2/26/2025 6:25 PM, Dmitry Baryshkov wrote:
> The LVDS/LCDC controller uses pixel clock coming from the multimedia
> controller (mmcc) rather than using the PLL directly. Stop using LVDS
> PLL directly and register it as a clock provider. Use lcdc_clk as a
> pixel clock for the LCDC.
> 
> Reviewed-by: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
> Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
> ---
>   drivers/gpu/drm/msm/disp/mdp4/mdp4_kms.h          |  2 +-
>   drivers/gpu/drm/msm/disp/mdp4/mdp4_lcdc_encoder.c |  8 +++++++-
>   drivers/gpu/drm/msm/disp/mdp4/mdp4_lvds_pll.c     | 22 +++++++---------------
>   3 files changed, 15 insertions(+), 17 deletions(-)
> 
> diff --git a/drivers/gpu/drm/msm/disp/mdp4/mdp4_kms.h b/drivers/gpu/drm/msm/disp/mdp4/mdp4_kms.h
> index 142ccb68b435263f91ba1ab27676e426d43e5d84..b8bdc3712c73b14f3547dce3439a895e3d10f193 100644
> --- a/drivers/gpu/drm/msm/disp/mdp4/mdp4_kms.h
> +++ b/drivers/gpu/drm/msm/disp/mdp4/mdp4_kms.h
> @@ -207,6 +207,6 @@ static inline struct drm_encoder *mdp4_dsi_encoder_init(struct drm_device *dev)
>   }
>   #endif
>   
> -struct clk *mpd4_lvds_pll_init(struct drm_device *dev);
> +int mpd4_lvds_pll_init(struct drm_device *dev);
>   
>   #endif /* __MDP4_KMS_H__ */
> diff --git a/drivers/gpu/drm/msm/disp/mdp4/mdp4_lcdc_encoder.c b/drivers/gpu/drm/msm/disp/mdp4/mdp4_lcdc_encoder.c
> index 8bbc7fb881d599e7d309cc61bda83697fecd253a..db93795916cdaa87ac8e61d3b44c2dadac10fd9e 100644
> --- a/drivers/gpu/drm/msm/disp/mdp4/mdp4_lcdc_encoder.c
> +++ b/drivers/gpu/drm/msm/disp/mdp4/mdp4_lcdc_encoder.c
> @@ -381,7 +381,13 @@ struct drm_encoder *mdp4_lcdc_encoder_init(struct drm_device *dev,
>   	drm_encoder_helper_add(encoder, &mdp4_lcdc_encoder_helper_funcs);
>   
>   	/* TODO: do we need different pll in other cases? */
> -	mdp4_lcdc_encoder->lcdc_clk = mpd4_lvds_pll_init(dev);
> +	ret = mpd4_lvds_pll_init(dev);
> +	if (ret) {
> +		DRM_DEV_ERROR(dev->dev, "failed to register LVDS PLL\n");
> +		return ERR_PTR(ret);
> +	}
> +
> +	mdp4_lcdc_encoder->lcdc_clk = devm_clk_get(dev->dev, "lcdc_clk");
>   	if (IS_ERR(mdp4_lcdc_encoder->lcdc_clk)) {
>   		DRM_DEV_ERROR(dev->dev, "failed to get lvds_clk\n");
>   		return ERR_CAST(mdp4_lcdc_encoder->lcdc_clk);

Change seems fine to me, one question on the order of changes, DT change 
has to be merged first otherwise it will fail here?

Will that be managed by co-ordinating with the DT maintainer?

> diff --git a/drivers/gpu/drm/msm/disp/mdp4/mdp4_lvds_pll.c b/drivers/gpu/drm/msm/disp/mdp4/mdp4_lvds_pll.c
> index ab8c0c187fb2cd05e26f5019244af15f1b2470c8..cbd154c72e44c848fa65fe01d848879b9f6735fb 100644
> --- a/drivers/gpu/drm/msm/disp/mdp4/mdp4_lvds_pll.c
> +++ b/drivers/gpu/drm/msm/disp/mdp4/mdp4_lvds_pll.c
> @@ -133,29 +133,21 @@ static struct clk_init_data pll_init = {
>   	.num_parents = ARRAY_SIZE(mpd4_lvds_pll_parents),
>   };
>   
> -struct clk *mpd4_lvds_pll_init(struct drm_device *dev)
> +int mpd4_lvds_pll_init(struct drm_device *dev)
>   {
>   	struct mdp4_lvds_pll *lvds_pll;
> -	struct clk *clk;
>   	int ret;
>   
>   	lvds_pll = devm_kzalloc(dev->dev, sizeof(*lvds_pll), GFP_KERNEL);
> -	if (!lvds_pll) {
> -		ret = -ENOMEM;
> -		goto fail;
> -	}
> +	if (!lvds_pll)
> +		return -ENOMEM;
>   
>   	lvds_pll->dev = dev;
>   
>   	lvds_pll->pll_hw.init = &pll_init;
> -	clk = devm_clk_register(dev->dev, &lvds_pll->pll_hw);
> -	if (IS_ERR(clk)) {
> -		ret = PTR_ERR(clk);
> -		goto fail;
> -	}
> +	ret = devm_clk_hw_register(dev->dev, &lvds_pll->pll_hw);
> +	if (ret)
> +		return ret;
>   
> -	return clk;
> -
> -fail:
> -	return ERR_PTR(ret);
> +	return devm_of_clk_add_hw_provider(dev->dev, of_clk_hw_simple_get, &lvds_pll->pll_hw);
>   }
>