linux-kernel - Re: [PATCH v2 1/3] drm/sun4i: dsi: Fix video start delay computation

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Message-ID: <20191007115148.vlu2ptmrfyng4p3r@gilmour>
Date:   Mon, 7 Oct 2019 13:51:48 +0200
From:   Maxime Ripard <mripard@...nel.org>
To:     Icenowy Zheng <icenowy@...c.io>
Cc:     Chen-Yu Tsai <wens@...e.org>,
        Jagan Teki <jagan@...rulasolutions.com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        dri-devel@...ts.freedesktop.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-sunxi@...glegroups.com, Merlijn Wajer <merlijn@...zup.org>
Subject: Re: [PATCH v2 1/3] drm/sun4i: dsi: Fix video start delay computation

On Mon, Oct 07, 2019 at 12:03:00AM +0800, Icenowy Zheng wrote:
> From: Jagan Teki <jagan@...rulasolutions.com>
>
> 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@...zup.org>
> Signed-off-by: Jagan Teki <jagan@...rulasolutions.com>

you should have your SoB here.

All the patches look fine, so there's no need to resend a new
version. I'll add it if you can give it.

Maxime

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