On Saturday 29 September 2018 08:57 PM, Maxime Ripard wrote:
On Thu, Sep 27, 2018 at 11:03:19PM +0530, Jagan Teki wrote:
On Thu, Sep 27, 2018 at 10:44 PM Maxime Ripard
<maxime.ripard@xxxxxxxxxxx> wrote:
On Thu, Sep 27, 2018 at 05:18:46PM +0530, Jagan Teki wrote:
Accordingly to BPI-M64-bsp DE DSI code Video start delay
can be computed by subtracting total vertical timing with
front porch timing and with adding 1 delay line for TCON.
This is what the current code is doing as well.
The current code
return mode->vtotal - (mode->vsync_end - mode->vdisplay) + 1;
(mode->vsync_end - mode->vdisplay) = front porch + sync
but I'm updating here only front porch.
This patch simply add the start_delay logic from BPI-M64-bsp,
w/o this new computation, the DSI on A64 encounter vblank time out.
[CRTC:36:crtc-0] vblank wait timed out
Signed-off-by: Jagan Teki <jagan@xxxxxxxxxxxxxxxxxxxx>
---
drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c | 12 +++++++++++-
1 file changed, 11 insertions(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
index 9918fdb990ff..217db74c6dc3 100644
--- a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
+++ b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
@@ -358,7 +358,17 @@ static void sun6i_dsi_inst_init(struct sun6i_dsi *dsi,
static u16 sun6i_dsi_get_video_start_delay(struct sun6i_dsi *dsi,
struct drm_display_mode *mode)
{
- return mode->vtotal - (mode->vsync_end - mode->vdisplay) + 1;
+ u32 vfp = mode->vsync_start - mode->vdisplay;
let me explain this.
Actual code from Allwinner
u32 vfp = panel->lcd_vt - panel->lcd_y - panel->lcd_vbp;
So,
=> (panel->lcd_vt - panel->lcd_y) - (panel->lcd_vbp)
=> (front porch + sync + back porch) - (back porch + sync)
Unless Allwinner is doing something fishy, in which case that should
be mentionned, the back porch doesn't contain the sync pulse.
As per as I understand panel->lcd_vbp is not back porch timings value
which i used by drm. It is BSP DTS property value and actual back porch
is calculated as "panel->lcd_vbp - panel->sync"
timmings->ver_sync_time= panel_info->lcd_vspw;
timmings->ver_back_porch= panel_info->lcd_vbp-panel_info->lcd_vspw;
