On Tue, Dec 11, 2018 at 10:30:08PM +0530, Jagan Teki wrote:

On Tue, Dec 11, 2018 at 10:19 PM Maxime Ripard
[off-list ref] wrote:

quoted

On Mon, Dec 10, 2018 at 09:47:19PM +0530, Jagan Teki wrote:

quoted

Video start delay can be computed by subtracting total vertical
timing with front porch timing and with adding 1 delay line for TCON.

BSP code form BPI-M64-bsp is computing video start delay as
(from linux-sunxi/
drivers/video/sunxi/disp2/disp/de/lowlevel_sun50iw1/de_dsi.c)

u32 vfp = panel->lcd_vt - panel->lcd_y - panel->lcd_vbp;
=> (panel->lcd_vt) - panel->lcd_y - (panel->lcd_vbp)
=> (timmings->ver_front_porch + panel->lcd_vbp + panel->lcd_y)
   - panel->lcd_y - (panel->lcd_vbp)
=> timmings->ver_front_porch + panel->lcd_vbp + panel->lcd_y
                           - panel->lcd_y - panel->lcd_vbp
=> timmings->ver_front_porch

So, update the start delay computation accordingly.

Signed-off-by: Jagan Teki <jagan@amarulasolutions.com>

Even though it's a bit better now on my A33 board and I don't have the
white stripes on the bottom of the display, there's still some
flickering with your patches applied.

Bisecting it seems to point at that patch, but reverting it doesn't
make the issue go away, so it's not really clear which one exactly is
at fault.

So, just like I asked in your v4, twice,

http://lists.infradead.org/pipermail/linux-arm-kernel/2018-November/615339.html

I don't know how can I comment here. Not quite clearly understand your
setup, because I have verified 3 different panels from different
vendors one with 2-lane, another with 4-lane and one with video format
and another one is burstmode format. I even verified with the clock
rate and register details.

Please suggest me, what can look further on this.

You had a reason to do these patches in the first place, yet you never
mention it anywhere in your commit logs. it would address the first
part of my comment.

And I can help you nail down whatever is going on here, but I would
need the panel datasheet for that. It is my second point.

Maxime

-- 
Maxime Ripard, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com