Re: [linux-sunxi] Re: [PATCH v10 03/11] drm/sun4i: dsi: Fix video start delay computation

[Chen-Yu Tsai <wens@csie.org>]

On Fri, May 24, 2019 at 6:27 PM Jagan Teki <jagan@amarulasolutions.com> wrote:
>
> On Fri, May 24, 2019 at 2:18 AM Maxime Ripard <maxime.ripard@bootlin.com> wrote:
> >
> > On Mon, May 20, 2019 at 02:33:10PM +0530, Jagan Teki wrote:
> > > 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
> >
> > The comment on patch 1 still applies on this patch
>
> Thanks, I have responded on that. Same applies here.

So this patch fixes the misinterpretation of Allwinner's back porch value,
much like patch 1, but this one is for the vertical back porch. So I think
you should follow the same advice I gave you for patch 1.

ChenYu

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