linux-kernel - Re: [PATCH v6 3/3] drm/stm: ltdc: add lvds pixel clock

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Date: Fri, 21 Jun 2024 16:55:42 +0200
From: Yannick FERTRE <yannick.fertre@...s.st.com>
To: Raphael Gallais-Pou <raphael.gallais-pou@...s.st.com>,
        David Airlie
	<airlied@...il.com>, Daniel Vetter <daniel@...ll.ch>,
        Maarten Lankhorst
	<maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <mripard@...nel.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley
	<conor+dt@...nel.org>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Alexandre
 Torgue <alexandre.torgue@...s.st.com>,
        Philippe Cornu
	<philippe.cornu@...s.st.com>,
        Philipp Zabel <p.zabel@...gutronix.de>
CC: <dri-devel@...ts.freedesktop.org>, <devicetree@...r.kernel.org>,
        <linux-stm32@...md-mailman.stormreply.com>,
        <linux-arm-kernel@...ts.infradead.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v6 3/3] drm/stm: ltdc: add lvds pixel clock

Hi Raphaël,

Thanks for your patch, it will not merged due to a new clock management.

Philippe,

this patch will be replaced by another which manages all clocks that the 
display controller

  will need (pixel clock, bus clock reference clock).


Best regards


Le 26/02/2024 à 11:48, Raphael Gallais-Pou a écrit :
> The STM32MP25x display subsystem presents a mux which feeds the loopback
> pixel clock of the current bridge in use into the LTDC. This mux is only
> accessible through sysconfig registers which is not yet available in the
> STM32MP25x common clock framework.
>
> While waiting for a complete update of the clock framework, this would
> allow to use the LVDS.
>
> Signed-off-by: Raphael Gallais-Pou <raphael.gallais-pou@...s.st.com>
> Signed-off-by: Yannick Fertre <yannick.fertre@...s.st.com>
> ---
> Changes in v2:
> 	- Fixed my address
> 	- Fixed smatch warning
> ---
>   drivers/gpu/drm/stm/ltdc.c | 19 +++++++++++++++++++
>   drivers/gpu/drm/stm/ltdc.h |  1 +
>   2 files changed, 20 insertions(+)
>
> diff --git a/drivers/gpu/drm/stm/ltdc.c b/drivers/gpu/drm/stm/ltdc.c
> index 5576fdae4962..23011a8913bd 100644
> --- a/drivers/gpu/drm/stm/ltdc.c
> +++ b/drivers/gpu/drm/stm/ltdc.c
> @@ -838,6 +838,12 @@ ltdc_crtc_mode_valid(struct drm_crtc *crtc,
>   	int target_max = target + CLK_TOLERANCE_HZ;
>   	int result;
>   
> +	if (ldev->lvds_clk) {
> +		result = clk_round_rate(ldev->lvds_clk, target);
> +		DRM_DEBUG_DRIVER("lvds pixclk rate target %d, available %d\n",
> +				 target, result);
> +	}
> +
>   	result = clk_round_rate(ldev->pixel_clk, target);
>   
>   	DRM_DEBUG_DRIVER("clk rate target %d, available %d\n", target, result);
> @@ -1896,6 +1902,8 @@ void ltdc_suspend(struct drm_device *ddev)
>   
>   	DRM_DEBUG_DRIVER("\n");
>   	clk_disable_unprepare(ldev->pixel_clk);
> +	if (ldev->lvds_clk)
> +		clk_disable_unprepare(ldev->lvds_clk);
>   }
>   
>   int ltdc_resume(struct drm_device *ddev)
> @@ -1910,6 +1918,13 @@ int ltdc_resume(struct drm_device *ddev)
>   		DRM_ERROR("failed to enable pixel clock (%d)\n", ret);
>   		return ret;
>   	}
> +	if (ldev->lvds_clk) {
> +		if (clk_prepare_enable(ldev->lvds_clk)) {
> +			clk_disable_unprepare(ldev->pixel_clk);
> +			DRM_ERROR("Unable to prepare lvds clock\n");
> +			return -ENODEV;
> +		}
> +	}
>   
>   	return 0;
>   }
> @@ -1981,6 +1996,10 @@ int ltdc_load(struct drm_device *ddev)
>   		}
>   	}
>   
> +	ldev->lvds_clk = devm_clk_get(dev, "lvds");
> +	if (IS_ERR(ldev->lvds_clk))
> +		ldev->lvds_clk = NULL;
> +
>   	rstc = devm_reset_control_get_exclusive(dev, NULL);
>   
>   	mutex_init(&ldev->err_lock);
> diff --git a/drivers/gpu/drm/stm/ltdc.h b/drivers/gpu/drm/stm/ltdc.h
> index 9d488043ffdb..4a60ce5b610c 100644
> --- a/drivers/gpu/drm/stm/ltdc.h
> +++ b/drivers/gpu/drm/stm/ltdc.h
> @@ -44,6 +44,7 @@ struct ltdc_device {
>   	void __iomem *regs;
>   	struct regmap *regmap;
>   	struct clk *pixel_clk;	/* lcd pixel clock */
> +	struct clk *lvds_clk;	/* lvds pixel clock */
>   	struct mutex err_lock;	/* protecting error_status */
>   	struct ltdc_caps caps;
>   	u32 irq_status;
>