drm/sun4i: dsi: Fix video start delay computation
authorJagan Teki <jagan@amarulasolutions.com>
Sun, 6 Oct 2019 16:03:00 +0000 (00:03 +0800)
committerMaxime Ripard <mripard@kernel.org>
Tue, 8 Oct 2019 05:56:41 +0000 (07:56 +0200)
commit9a197c862f0d0863a61715a056c16b07d18aa5d8
tree3ecca68462d63169425727a5204eab3e7104145f
parentfba3baa8d2be7b37748e0ed8345d2d3d6f17f9fd
drm/sun4i: dsi: Fix video start delay computation

The LCD timing definitions between Linux DRM vs Allwinner are different,
below diagram shows this clear differences.

           Active                 Front           Sync           Back
           Region                 Porch                          Porch
<-----------------------><----------------><--------------><-------------->
  //////////////////////|
 ////////////////////// |
//////////////////////  |..................                ................
                                           ________________
<----- [hv]display ----->
<------------- [hv]sync_start ------------>
<--------------------- [hv]sync_end ---------------------->
<-------------------------------- [hv]total ------------------------------>

<----- lcd_[xy] -------->   <- lcd_[hv]spw ->
  <---------- lcd_[hv]bp --------->
<-------------------------------- lcd_[hv]t ------------------------------>

The DSI driver misinterpreted the vbp term from the BSP code to refer
only to the backporch, when in fact it was backporch + sync. Thus the
driver incorrectly used the vertical front porch plus sync in its
calculation of the DRQ set bit value, when it should not have included
the sync timing.

Including additional sync timings leads to 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

With the terms(as described in above diagram) fixed, the panel
displays correctly without any timeouts.

Tested-by: Merlijn Wajer <merlijn@wizzup.org>
Signed-off-by: Jagan Teki <jagan@amarulasolutions.com>
Signed-off-by: Icenowy Zheng <icenowy@aosc.io>
Signed-off-by: Maxime Ripard <mripard@kernel.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20191006160303.24413-2-icenowy@aosc.io
drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c