On Thu, Nov 15, 2018 at 11:19:53PM +0530, Jagan Teki wrote:

On Thu, Nov 15, 2018 at 3:26 PM Maxime Ripard [off-list ref] wrote:

quoted

Hi,

On Tue, Nov 13, 2018 at 04:46:15PM +0530, Jagan Teki wrote:

quoted

The horizontal and vertical back porch calculation in BSP
code is simply following the Linux drm comment diagram, in
include/drm/drm_modes.h which is

[hv]back porch = [hv]total - [hv]sync_end

BSP code form BPI-M64-bsp is calculating vertical back porch as
(from linux-sunxi/drivers/video/sunxi/disp2/disp/de/disp_lcd.c)

timmings->ver_sync_time= panel_info->lcd_vspw;
timmings->ver_back_porch= panel_info->lcd_vbp-panel_info->lcd_vspw;

vbp = panel->lcd_vbp;
vspw = panel->lcd_vspw;
dsi_dev[sel]->dsi_basic_size0.bits.vbp = vbp-vspw;
dsi_dev[sel]->dsi_basic_size0.bits.vbp = panel->lcd_vbp - panel->lcd_vspw;
=>  timmings->ver_back_porch + panel_info->lcd_vspw - panel_info->lcd_vspw
=>  timmings->ver_back_porch
=>  mode->vtotal - mode->end

Which evatually same as mode->vtotal - mode->vsync_end so update the
same in SUN6I_DSI_BASIC_SIZE0_VBP

On the information note, existing SUN6I_DSI_BASIC_SIZE0_VSA is proper
value.

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

I've tested your changes on my A33 board, and this commit will break
it.

It creates vblank timeouts, and visual artifacts at the bottom of the
display.

Strange, VBP is earlier gives front porch which is anyway wrong.

quoted

Later commits seem to fix the issue, but will create some blanking on
the upper third of the display.

Since the documentation is quite sparse, and a MIPI-DSI analyzer is
way too expensive, I'd really like to have at least what each of these
commits are actually fixing, and what symptoms each of these were
causing, and not just "the BSP does it".

W/o this 2-lane panel is breaking, same vblank timeout and visual
artifacts at the bottom of the panel. though the commits may reference
BSP, I have at-least tested on 3 different panels for us to prove its
working.

quoted

Having some datasheet for the panels you had working would help too.

Unfortunately datasheet doesn't have any required information what we
actually looking for.

Not even the timings? How did you get that information then?

Maxime

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