The current code is computing vertical video start delay as
delay = mode->vtotal - (mode->vsync_end - mode->vdisplay) + start;
On which the second parameter
mode->vsync_end - mode->vdisplay = front porch + sync timings
according to "DRM kernel-internal display mode structure" in
include/drm/drm_modes.h
With adding additional sync timings, the desired video start delay
value as 510 for "bananapi,s070wv20-ct16" panel timings which indeed
trigger panel flip_done timed out as:
WARNING: CPU: 0 PID: 31 at drivers/gpu/drm/drm_atomic_helper.c:1429 drm_atomic_helper_wait_for_vblanks.part.1+0x298/0x2a0
[CRTC:46:crtc-0] vblank wait timed out
Modules linked in:
CPU: 0 PID: 31 Comm: kworker/0:1 Not tainted 5.1.0-next-20190514-00029-g09e5b0ed0a58 #18
Hardware name: Allwinner sun8i Family
Workqueue: events deferred_probe_work_func
[<c010ed54>] (unwind_backtrace) from [<c010b76c>] (show_stack+0x10/0x14)
[<c010b76c>] (show_stack) from [<c0688c70>] (dump_stack+0x84/0x98)
[<c0688c70>] (dump_stack) from [<c011d9e4>] (__warn+0xfc/0x114)
[<c011d9e4>] (__warn) from [<c011da40>] (warn_slowpath_fmt+0x44/0x68)
[<c011da40>] (warn_slowpath_fmt) from [<c040cd50>] (drm_atomic_helper_wait_for_vblanks.part.1+0x298/0x2a0)
[<c040cd50>] (drm_atomic_helper_wait_for_vblanks.part.1) from [<c040e694>] (drm_atomic_helper_commit_tail_rpm+0x5c/0x6c)
[<c040e694>] (drm_atomic_helper_commit_tail_rpm) from [<c040e4dc>] (commit_tail+0x40/0x6c)
[<c040e4dc>] (commit_tail) from [<c040e5cc>] (drm_atomic_helper_commit+0xbc/0x128)
[<c040e5cc>] (drm_atomic_helper_commit) from [<c0411b64>] (restore_fbdev_mode_atomic+0x1cc/0x1dc)
[<c0411b64>] (restore_fbdev_mode_atomic) from [<c04156f8>] (drm_fb_helper_restore_fbdev_mode_unlocked+0x54/0xa0)
[<c04156f8>] (drm_fb_helper_restore_fbdev_mode_unlocked) from [<c0415774>] (drm_fb_helper_set_par+0x30/0x54)
[<c0415774>] (drm_fb_helper_set_par) from [<c03ad450>] (fbcon_init+0x560/0x5ac)
[<c03ad450>] (fbcon_init) from [<c03eb8a0>] (visual_init+0xbc/0x104)
[<c03eb8a0>] (visual_init) from [<c03ed1b8>] (do_bind_con_driver+0x1b0/0x390)
[<c03ed1b8>] (do_bind_con_driver) from [<c03ed780>] (do_take_over_console+0x13c/0x1c4)
[<c03ed780>] (do_take_over_console) from [<c03ad800>] (do_fbcon_takeover+0x74/0xcc)
[<c03ad800>] (do_fbcon_takeover) from [<c013c9c8>] (notifier_call_chain+0x44/0x84)
[<c013c9c8>] (notifier_call_chain) from [<c013cd20>] (__blocking_notifier_call_chain+0x48/0x60)
[<c013cd20>] (__blocking_notifier_call_chain) from [<c013cd50>] (blocking_notifier_call_chain+0x18/0x20)
[<c013cd50>] (blocking_notifier_call_chain) from [<c03a6e44>] (register_framebuffer+0x1e0/0x2f8)
[<c03a6e44>] (register_framebuffer) from [<c04153c0>] (__drm_fb_helper_initial_config_and_unlock+0x2fc/0x50c)
[<c04153c0>] (__drm_fb_helper_initial_config_and_unlock) from [<c04158c8>] (drm_fbdev_client_hotplug+0xe8/0x1b8)
[<c04158c8>] (drm_fbdev_client_hotplug) from [<c0415a20>] (drm_fbdev_generic_setup+0x88/0x118)
[<c0415a20>] (drm_fbdev_generic_setup) from [<c043f060>] (sun4i_drv_bind+0x128/0x160)
[<c043f060>] (sun4i_drv_bind) from [<c044b598>] (try_to_bring_up_master+0x164/0x1a0)
[<c044b598>] (try_to_bring_up_master) from [<c044b668>] (__component_add+0x94/0x140)
[<c044b668>] (__component_add) from [<c0445e1c>] (sun6i_dsi_probe+0x144/0x234)
[<c0445e1c>] (sun6i_dsi_probe) from [<c0452ef4>] (platform_drv_probe+0x48/0x9c)
[<c0452ef4>] (platform_drv_probe) from [<c04512cc>] (really_probe+0x1dc/0x2c8)
[<c04512cc>] (really_probe) from [<c0451518>] (driver_probe_device+0x60/0x160)
[<c0451518>] (driver_probe_device) from [<c044f7a4>] (bus_for_each_drv+0x74/0xb8)
[<c044f7a4>] (bus_for_each_drv) from [<c045107c>] (__device_attach+0xd0/0x13c)
[<c045107c>] (__device_attach) from [<c0450474>] (bus_probe_device+0x84/0x8c)
[<c0450474>] (bus_probe_device) from [<c0450900>] (deferred_probe_work_func+0x64/0x90)
[<c0450900>] (deferred_probe_work_func) from [<c0135970>] (process_one_work+0x204/0x420)
[<c0135970>] (process_one_work) from [<c013690c>] (worker_thread+0x274/0x5a0)
[<c013690c>] (worker_thread) from [<c013b3d8>] (kthread+0x11c/0x14c)
[<c013b3d8>] (kthread) from [<c01010e8>] (ret_from_fork+0x14/0x2c)
Exception stack(0xde539fb0 to 0xde539ff8)
9fa0: 00000000 00000000 00000000 00000000
9fc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
9fe0: 00000000 00000000 00000000 00000000 00000013 00000000
---[ end trace 495200a78b24980e ]---
random: fast init done
[drm:drm_atomic_helper_wait_for_dependencies] *ERROR* [CRTC:46:crtc-0] flip_done timed out
[drm:drm_atomic_helper_wait_for_dependencies] *ERROR* [CONNECTOR:48:DSI-1] flip_done timed out
[drm:drm_atomic_helper_wait_for_dependencies] *ERROR* [PLANE:30:plane-0] flip_done timed out
But the expected video start delay value is 513 which states that
the second parameter on the computation is "front porch" value
(no sync timings included).
This is clearly confirmed from the legacy [1] and new [2] bsp codes
that the second parameter on the video start delay is "front porch"
Here is the detailed evidence for calculating front porch as per
bsp code.
vfp = panel->lcd_vt - panel->lcd_y - panel->lcd_vbp
=> (panel->lcd_vt) - panel->lcd_y - panel->lcd_vbp
=> (tt->ver_front_porch + lcdp->panel_info.lcd_vbp
+ lcdp->panel_info.lcd_y) - panel->lcd_y - panel->lcd_vbp
=> tt->ver_front_porch
Which is mode->vsync_start - mode->vdisplay according to
"DRM kernel-internal display mode structure" in include/drm/drm_modes.h
This patch fix this by updating the video start delay to use
front porch value.
[2] https://github.com/BPI-SINOVOIP/BPI-M2M-bsp/blob/master/linux-sunxi/drivers/video/sunxi/disp/de/disp_lcd.c#L2051
[1] https://github.com/BPI-SINOVOIP/BPI-M2M-bsp/blob/master/linux-sunxi/drivers/video/sunxi/disp/de/lowlevel_sun8iw5/de_dsi.c#L803
Signed-off-by: Jagan Teki <jagan@xxxxxxxxxxxxxxxxxxxx>
---
drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
index b3ca85410b2c..47d571d97600 100644
--- a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
+++ b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
@@ -375,7 +375,7 @@ static u16 sun6i_dsi_get_video_start_delay(struct sun6i_dsi *dsi,
* working in all supported panels as of now.
*/
u8 start = 1;
- u16 delay = mode->vtotal - (mode->vsync_end - mode->vdisplay) + start;
+ u16 delay = mode->vtotal - (mode->vsync_start - mode->vdisplay) + start;
if (delay > mode->vtotal)
delay = delay % mode->vtotal;
--
2.18.0.321.gffc6fa0e3
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