linux-kernel - Re: [PATCH] drm/stm: ltdc: filter mode pixel clock vs pad constraint

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Message-ID: <e1c4deef-ba3a-6454-a0cf-b05c144c58b5@st.com>
Date:   Tue, 3 Jul 2018 11:01:57 +0000
From:   Philippe CORNU <philippe.cornu@...com>
To:     Yannick FERTRE <yannick.fertre@...com>,
        Benjamin Gaignard <benjamin.gaignard@...aro.org>,
        Vincent ABRIOU <vincent.abriou@...com>,
        "David Airlie" <airlied@...ux.ie>,
        "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] drm/stm: ltdc: filter mode pixel clock vs pad constraint

Hi Yannick,

On 06/29/2018 01:22 PM, Yannick Fertre wrote:
> Filter the requested mode pixel clock frequency according
> to the pad maximum supported frequency.
> 
> Signed-off-by: Yannick Fertre <yannick.fertre@...com>
> ---
>   drivers/gpu/drm/stm/ltdc.c | 16 ++++++++++++----
>   drivers/gpu/drm/stm/ltdc.h |  1 +
>   2 files changed, 13 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/gpu/drm/stm/ltdc.c b/drivers/gpu/drm/stm/ltdc.c
> index 00e3262..96d20c2 100644
> --- a/drivers/gpu/drm/stm/ltdc.c
> +++ b/drivers/gpu/drm/stm/ltdc.c
> @@ -491,6 +491,14 @@ static void ltdc_crtc_atomic_disable(struct drm_crtc *crtc,
>   	int target_max = target + CLK_TOLERANCE_HZ;
>   	int result;
>   
> +	result = clk_round_rate(ldev->pixel_clk, target);
> +
> +	DRM_DEBUG_DRIVER("clk rate target %d, available %d\n", target, result);
> +
> +	/* Filter modes according to the max frequency supported by the pads */
> +	if (result > ldev->caps.pad_max_freq_hz)
> +		return MODE_CLOCK_HIGH;
> +
>   	/*
>   	 * Accept all "preferred" modes:
>   	 * - this is important for panels because panel clock tolerances are
> @@ -502,10 +510,6 @@ static void ltdc_crtc_atomic_disable(struct drm_crtc *crtc,
>   	if (mode->type & DRM_MODE_TYPE_PREFERRED)
>   		return MODE_OK;
>   
> -	result = clk_round_rate(ldev->pixel_clk, target);
> -
> -	DRM_DEBUG_DRIVER("clk rate target %d, available %d\n", target, result);
> -
>   	/*
>   	 * Filter modes according to the clock value, particularly useful for
>   	 * hdmi modes that require precise pixel clocks.
> @@ -1039,11 +1043,15 @@ static int ltdc_get_caps(struct drm_device *ddev)
>   		 * does not work on 2nd layer.
>   		 */
>   		ldev->caps.non_alpha_only_l1 = true;
> +		ldev->caps.pad_max_freq_hz = 90000000;
> +		if (ldev->caps.hw_version == HWVER_10200)
> +			ldev->caps.pad_max_freq_hz = 65000000;
>   		break;
>   	case HWVER_20101:
>   		ldev->caps.reg_ofs = REG_OFS_4;
>   		ldev->caps.pix_fmt_hw = ltdc_pix_fmt_a1;
>   		ldev->caps.non_alpha_only_l1 = false;
> +		ldev->caps.pad_max_freq_hz = 150000000;
>   		break;
>   	default:
>   		return -ENODEV;
> diff --git a/drivers/gpu/drm/stm/ltdc.h b/drivers/gpu/drm/stm/ltdc.h
> index c14e4db..0294d38 100644
> --- a/drivers/gpu/drm/stm/ltdc.h
> +++ b/drivers/gpu/drm/stm/ltdc.h
> @@ -20,6 +20,7 @@ struct ltdc_caps {
>   	u32 bus_width;		/* bus width (32 or 64 bits) */
>   	const u32 *pix_fmt_hw;	/* supported pixel formats */
>   	bool non_alpha_only_l1; /* non-native no-alpha formats on layer 1 */
> +	int pad_max_freq_hz;	/* max frequency supported by pad */

Thank you for your patch,

Reviewed-by: Philippe Cornu <philippe.cornu@...com>
Tested-by: Philippe Cornu <philippe.cornu@...com>

Philippe :-)

>   };
>   
>   #define LTDC_MAX_LAYER	4
>