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* [PATCH] drm: rcar-du: Extend CMM HDSE documentation
@ 2022-04-09 18:57 ` Kieran Bingham
  0 siblings, 0 replies; 4+ messages in thread
From: Kieran Bingham @ 2022-04-09 18:57 UTC (permalink / raw)
  To: linux-renesas-soc, dri-devel
  Cc: Kieran Bingham, Laurent Pinchart, David Airlie, Daniel Vetter,
	open list

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@ideasonboard.com>
Signed-off-by: Kieran Bingham <kieran.bingham+renesas@ideasonboard.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;
-- 
2.32.0


^ permalink raw reply related	[flat|nested] 4+ messages in thread

end of thread, other threads:[~2022-04-10 15:22 UTC | newest]

Thread overview: 4+ messages (download: mbox.gz follow: Atom feed
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2022-04-09 18:57 [PATCH] drm: rcar-du: Extend CMM HDSE documentation Kieran Bingham
2022-04-09 18:57 ` Kieran Bingham
2022-04-10 15:22 ` Laurent Pinchart
2022-04-10 15:22   ` Laurent Pinchart

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