On Thu, Mar 08, 2012 at 04:31:51PM +0100, Laurent Pinchart wrote:
Hi Joonyoung,
On Thursday 08 March 2012 22:05:50 Joonyoung Shim wrote:
On 03/08/2012 08:34 PM, Laurent Pinchart wrote:
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 Pinchartlaurent.pinchart@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 ?
Good catch. You can refer Documentation/fb/framebuffer.txt to know in detail.
Acked-by: Joonyoung Shim jy0922.shim@samsung.com
Thank you. There's a similar issue in exynos_mipi_dsi_set_display_mode() where front and back porch are inverted. I'll submit a patch for that as well.
Damned. This seems to be a common misunderstanding. I never really thought about it and always assumed that 'front porch' and 'back porch' refers to the picture and not to the sync signal. I was so sure that I didn't even care to google it before I saw this patch.
Sascha