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Date:   Thu, 23 May 2019 22:38:36 +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 03/11] drm/sun4i: dsi: Fix video start delay
 computation
Message-ID: <20190523203836.xy7nmte3ubyxwg27@flea>
References: <20190520090318.27570-1-jagan@amarulasolutions.com>
 <20190520090318.27570-4-jagan@amarulasolutions.com>
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In-Reply-To: <20190520090318.27570-4-jagan@amarulasolutions.com>
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Sender: linux-kernel-owner@vger.kernel.org
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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

Maxime

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