Subject: [PATCH v11 1/7] drm/sun4i: dsi: Fix TCON DRQ set bits

From: Jagan Teki <[email-masked]>
Date: Thu, 3 Oct 2019 12:15:21 +0530

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 hbp term from the BSP code to refer
only to the backporch, when in fact it was backporch + sync. Thus the
driver incorrectly used the horizontal 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-20190514-00026-g01f0c75b902d-dirty #13
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 b57eb1e5c64c6b8b ]---
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 <[email-masked]>
Signed-off-by: Jagan Teki <[email-masked]>
---
 drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
index 1636344ba9ec..f83522717488 100644
--- a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
+++ b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
@@ -437,9 +437,9 @@ static void sun6i_dsi_setup_burst(struct sun6i_dsi *dsi,
 			     SUN6I_DSI_BURST_LINE_SYNC_POINT(SUN6I_DSI_SYNC_POINT));
 
 		val = SUN6I_DSI_TCON_DRQ_ENABLE_MODE;
-	} else if ((mode->hsync_end - mode->hdisplay) > 20) {
+	} else if ((mode->hsync_start - mode->hdisplay) > 20) {
 		/* Maaaaaagic */
-		u16 drq = (mode->hsync_end - mode->hdisplay) - 20;
+		u16 drq = (mode->hsync_start - mode->hdisplay) - 20;
 
 		drq *= mipi_dsi_pixel_format_to_bpp(device->format);
 		drq /= 32;
-- 
2.18.0.321.gffc6fa0e3

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