linux-kernel - Re: [PATCH] drm: rcar-du: Extend CMM HDSE documentation

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Message-ID: <YlL2KuYPyByjtbsL@pendragon.ideasonboard.com>
Date:   Sun, 10 Apr 2022 18:22:18 +0300
From:   Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:     Kieran Bingham <kieran.bingham+renesas@...asonboard.com>
Cc:     linux-renesas-soc@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] drm: rcar-du: Extend CMM HDSE documentation

Hi Kieran,

Thank you for the patch.

On Sat, Apr 09, 2022 at 07:57:06PM +0100, Kieran Bingham wrote:
> When the CMM is enabled, the HDSE offset is further adjusted to
> compensate for consumed pixels.
> 
> Explain this further, with an extra comment at the point the offset is
> adjusted.
> 
> Suggested-by: Laurent Pinchart <laurent.pinchart@...asonboard.com>
> Signed-off-by: Kieran Bingham <kieran.bingham+renesas@...asonboard.com>

Reviewed-by: Laurent Pinchart <laurent.pinchart@...asonboard.com>

> ---
>  drivers/gpu/drm/rcar-du/rcar_du_crtc.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/drivers/gpu/drm/rcar-du/rcar_du_crtc.c b/drivers/gpu/drm/rcar-du/rcar_du_crtc.c
> index f361a604337f..23e1aedf8dc0 100644
> --- a/drivers/gpu/drm/rcar-du/rcar_du_crtc.c
> +++ b/drivers/gpu/drm/rcar-du/rcar_du_crtc.c
> @@ -300,6 +300,11 @@ static void rcar_du_crtc_set_display_timing(struct rcar_du_crtc *rcrtc)
>  	     | DSMR_DIPM_DISP | DSMR_CSPM;
>  	rcar_du_crtc_write(rcrtc, DSMR, dsmr);
>  
> +	/*
> +	 * When the CMM is enabled, an additional offset of 25 pixels must be
> +	 * subtracted from the HDS (horizontal display start) and HDE
> +	 * (horizontal display end) registers.
> +	 */
>  	hdse_offset = 19;
>  	if (rcrtc->group->cmms_mask & BIT(rcrtc->index % 2))
>  		hdse_offset += 25;

-- 
Regards,

Laurent Pinchart