[PATCH] drm: exynos: Fix fb_videomode <-> drm_mode_modeinfo conversion

[Laurent Pinchart]

The fb_videomode structure stores the front porch and back porch in the
right_margin and left_margin fields respectively. right_margin should
thus be computed with hsync_start - hdisplay, and left_margin with
htotal - hsync_end. The same holds for the vertical direction.

       Active               Front           Sync            Back
       Region               Porch                           Porch
<-------------------><----------------><-------------><---------------->

  //////////////////|
 ////////////////// |
//////////////////  |..................               ..................
                                       _______________

<------ xres -------><- right_margin -><- hsync_len -><- left_margin -->

<---- hdisplay ----->
<------------ hsync_start ------------>
<--------------------- hsync_end -------------------->
<--------------------------------- htotal ----------------------------->

Fix the fb_videomode <-> drm_mode_modeinfo conversion functions
accordingly.

Signed-off-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
---
 drivers/gpu/drm/exynos/exynos_drm_connector.c |   16 ++++++++--------
 1 files changed, 8 insertions(+), 8 deletions(-)

While trying to understand how the fb_videomode and drm_mode_modeinfo fields
map to each other, I found what might be a bug in the Exynos DRM driver. Could
you please check and confirm that my understanding is correct ?

diff --git a/drivers/gpu/drm/exynos/exynos_drm_connector.c b/drivers/gpu/drm/exynos/exynos_drm_connector.c
index d620b07..7bb1dca 100644
--- a/drivers/gpu/drm/exynos/exynos_drm_connector.c
+++ b/drivers/gpu/drm/exynos/exynos_drm_connector.c
@@ -52,14 +52,14 @@ convert_to_display_mode(struct drm_display_mode *mode,
 	mode->vrefresh = timing->refresh;
 
 	mode->hdisplay = timing->xres;
-	mode->hsync_start = mode->hdisplay + timing->left_margin;
+	mode->hsync_start = mode->hdisplay + timing->right_margin;
 	mode->hsync_end = mode->hsync_start + timing->hsync_len;
-	mode->htotal = mode->hsync_end + timing->right_margin;
+	mode->htotal = mode->hsync_end + timing->left_margin;
 
 	mode->vdisplay = timing->yres;
-	mode->vsync_start = mode->vdisplay + timing->upper_margin;
+	mode->vsync_start = mode->vdisplay + timing->lower_margin;
 	mode->vsync_end = mode->vsync_start + timing->vsync_len;
-	mode->vtotal = mode->vsync_end + timing->lower_margin;
+	mode->vtotal = mode->vsync_end + timing->upper_margin;
 
 	if (timing->vmode & FB_VMODE_INTERLACED)
 		mode->flags |= DRM_MODE_FLAG_INTERLACE;
@@ -81,14 +81,14 @@ convert_to_video_timing(struct fb_videomode *timing,
 	timing->refresh = drm_mode_vrefresh(mode);
 
 	timing->xres = mode->hdisplay;
-	timing->left_margin = mode->hsync_start - mode->hdisplay;
+	timing->right_margin = mode->hsync_start - mode->hdisplay;
 	timing->hsync_len = mode->hsync_end - mode->hsync_start;
-	timing->right_margin = mode->htotal - mode->hsync_end;
+	timing->left_margin = mode->htotal - mode->hsync_end;
 
 	timing->yres = mode->vdisplay;
-	timing->upper_margin = mode->vsync_start - mode->vdisplay;
+	timing->lower_margin = mode->vsync_start - mode->vdisplay;
 	timing->vsync_len = mode->vsync_end - mode->vsync_start;
-	timing->lower_margin = mode->vtotal - mode->vsync_end;
+	timing->upper_margin = mode->vtotal - mode->vsync_end;
 
 	if (mode->flags & DRM_MODE_FLAG_INTERLACE)
 		timing->vmode = FB_VMODE_INTERLACED;
-- 
Regards,

Laurent Pinchart