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Date:   Thu, 23 May 2019 22:37:54 +0200
From:   Maxime Ripard <maxime.ripard@bootlin.com>
To:     Jagan Teki <jagan@amarulasolutions.com>
Cc:     David Airlie <airlied@linux.ie>, Daniel Vetter <daniel@ffwll.ch>,
        Chen-Yu Tsai <wens@csie.org>, dri-devel@lists.freedesktop.org,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org,
        bshah@mykolab.com, Vasily Khoruzhick <anarsoul@gmail.com>,
        powerpan@qq.com, michael@amarulasolutions.com,
        linux-amarula@amarulasolutions.com, linux-sunxi@googlegroups.com
Subject: Re: [PATCH v10 02/11] drm/sun4i: dsi: Update start value in video
 start delay
Message-ID: <20190523203754.2lhi37veeh4rwiy3@flea>
References: <20190520090318.27570-1-jagan@amarulasolutions.com>
 <20190520090318.27570-3-jagan@amarulasolutions.com>
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On Mon, May 20, 2019 at 02:33:09PM +0530, Jagan Teki wrote:
> start value in video start delay computation done in below commit
> is as per the legacy bsp drivers/video/sunxi/legacy..
> "drm/sun4i: dsi: Change the start delay calculation"
> (sha1: da676c6aa6413d59ab0a80c97bbc273025e640b2)
>
> This existing start delay computation gives start value of 35,
> 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 Tainted: G        W         5.1.0-next-20190514-00025-gf928bc7cc146 #15
>  Hardware name: Allwinner sun8i Family
>  Workqueue: events deferred_probe_work_func
>  [<c010ed54>] (unwind_backtrace) from [<c010b76c>] (show_stack+0x10/0x14)
>  [<c010b76c>] (show_stack) from [<c0688c90>] (dump_stack+0x84/0x98)
>  [<c0688c90>] (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 [<c0411cb0>] (drm_fb_helper_pan_display+0xac/0x1d0)
>  [<c0411cb0>] (drm_fb_helper_pan_display) from [<c03a4e84>] (fb_pan_display+0xcc/0x134)
>  [<c03a4e84>] (fb_pan_display) from [<c03b1214>] (bit_update_start+0x14/0x30)
>  [<c03b1214>] (bit_update_start) from [<c03afe94>] (fbcon_switch+0x3d8/0x4e0)
>  [<c03afe94>] (fbcon_switch) from [<c03ec930>] (redraw_screen+0x174/0x238)
>  [<c03ec930>] (redraw_screen) from [<c03aceb4>] (fbcon_prepare_logo+0x3c4/0x400)
>  [<c03aceb4>] (fbcon_prepare_logo) from [<c03ad2b8>] (fbcon_init+0x3c8/0x5ac)
>  [<c03ad2b8>] (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 [<c044b5b0>] (try_to_bring_up_master+0x164/0x1a0)
>  [<c044b5b0>] (try_to_bring_up_master) from [<c044b680>] (__component_add+0x94/0x140)
>  [<c044b680>] (__component_add) from [<c0445e1c>] (sun6i_dsi_probe+0x144/0x234)
>  [<c0445e1c>] (sun6i_dsi_probe) from [<c0452f0c>] (platform_drv_probe+0x48/0x9c)
>  [<c0452f0c>] (platform_drv_probe) from [<c04512e4>] (really_probe+0x1dc/0x2c8)
>  [<c04512e4>] (really_probe) from [<c0451530>] (driver_probe_device+0x60/0x160)
>  [<c0451530>] (driver_probe_device) from [<c044f7bc>] (bus_for_each_drv+0x74/0xb8)
>  [<c044f7bc>] (bus_for_each_drv) from [<c0451094>] (__device_attach+0xd0/0x13c)
>  [<c0451094>] (__device_attach) from [<c045048c>] (bus_probe_device+0x84/0x8c)
>  [<c045048c>] (bus_probe_device) from [<c0450918>] (deferred_probe_work_func+0x64/0x90)
>  [<c0450918>] (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 755e10f62b83f396 ]---
>  Console: switching to colour frame buffer device 100x30
>  [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 start delay value is 1 which is confirmed from
> new bsp [2].

If you're saying that the "legacy" link (second one) is the new BSP.

> The important and unclear note on legacy and new bsp codes [1] [2]
> is both use similar start computation initially but it later reassign
> it to 1 in new bsp.

Then start_delay is never reassigned to 1 in that link, and is clamped
between 8 and 100 as the code that you are removing is doing.

> Unfortunately we don't have any evidence or documentation for this
> reassignment to 1 in new bsp, but it is working with all supported
> panels in A33, A64.

No, it's not. That was added to fix a panel that is supported today.

Maxime

--
Maxime Ripard, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com