drm: rcar-du: Extend CMM HDSE documentation
authorKieran Bingham <kieran.bingham+renesas@ideasonboard.com>
Sat, 9 Apr 2022 18:57:06 +0000 (19:57 +0100)
committerLaurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Thu, 7 Jul 2022 02:21:54 +0000 (05:21 +0300)
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>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
drivers/gpu/drm/rcar-du/rcar_du_crtc.c

index f361a604337f6c0a09f9accdd9fe555159f33f8a..23e1aedf8dc0243cb9e8341e623c7005a66d960b 100644 (file)
@@ -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;