linux-kernel - Re: [PATCH v2 1/3] gpu/drm: ingenic: Add trick to support 16bpp on 24-bit panels

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Message-Id: <BERG8Q.6W7J6M63PE2V2@crapouillou.net>
Date:   Wed, 08 Apr 2020 11:51:47 +0200
From:   Paul Cercueil <paul@...pouillou.net>
To:     Daniel Vetter <daniel@...ll.ch>, David Airlie <airlied@...ux.ie>
Cc:     od@...c.me, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/3] gpu/drm: ingenic: Add trick to support 16bpp on
 24-bit panels

Hi,

Any feedback for this patchset?

Thanks,
-Paul


Le mer. 26 févr. 2020 à 1:30, Paul Cercueil <paul@...pouillou.net> a 
écrit :
> If the panel interface is 24-bit but our primary plane is 16bpp,
> configure as if the panel was 18-bit. This tricks permits the display
> of 16bpp data on a 24-bit panel by wiring each color component to the
> MSBs of the 24-bit interface.
> 
> v2: Check bytes-per-pixel count instead of fourcc format
> 
> Signed-off-by: Paul Cercueil <paul@...pouillou.net>
> ---
>  drivers/gpu/drm/ingenic/ingenic-drm.c | 18 +++++++++++++++++-
>  1 file changed, 17 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/ingenic/ingenic-drm.c 
> b/drivers/gpu/drm/ingenic/ingenic-drm.c
> index 6d47ef7b148c..5493a80d7d2f 100644
> --- a/drivers/gpu/drm/ingenic/ingenic-drm.c
> +++ b/drivers/gpu/drm/ingenic/ingenic-drm.c
> @@ -400,6 +400,8 @@ static void 
> ingenic_drm_encoder_atomic_mode_set(struct drm_encoder *encoder,
>  	struct drm_display_mode *mode = &crtc_state->adjusted_mode;
>  	struct drm_connector *conn = conn_state->connector;
>  	struct drm_display_info *info = &conn->display_info;
> +	struct drm_plane_state *plane_state = 
> crtc_state->crtc->primary->state;
> +	const struct drm_format_info *finfo = NULL;
>  	unsigned int cfg;
> 
>  	priv->panel_is_sharp = info->bus_flags & DRM_BUS_FLAG_SHARP_SIGNALS;
> @@ -435,7 +437,21 @@ static void 
> ingenic_drm_encoder_atomic_mode_set(struct drm_encoder *encoder,
>  				cfg |= JZ_LCD_CFG_MODE_GENERIC_18BIT;
>  				break;
>  			case MEDIA_BUS_FMT_RGB888_1X24:
> -				cfg |= JZ_LCD_CFG_MODE_GENERIC_24BIT;
> +				if (plane_state && plane_state->fb)
> +					finfo = plane_state->fb->format;
> +
> +				/*
> +				 * If the panel interface is 24-bit but our
> +				 * primary plane is 16bpp, configure as if the
> +				 * panel was 18-bit. This tricks permits the
> +				 * display of 16bpp data on a 24-bit panel by
> +				 * wiring each color component to the MSBs of
> +				 * the 24-bit interface.
> +				 */
> +				if (finfo && finfo->cpp[0] < 3)
> +					cfg |= JZ_LCD_CFG_MODE_GENERIC_18BIT;
> +				else
> +					cfg |= JZ_LCD_CFG_MODE_GENERIC_24BIT;
>  				break;
>  			case MEDIA_BUS_FMT_RGB888_3X8:
>  				cfg |= JZ_LCD_CFG_MODE_8BIT_SERIAL;
> --
> 2.25.0
>