Message-id: <54FAECCA.2050201@samsung.com>
Date:	Sat, 07 Mar 2015 21:19:22 +0900
From:	Inki Dae <inki.dae@...sung.com>
To:	Charles Keepax <ckeepax@...nsource.wolfsonmicro.com>
Cc:	jy0922.shim@...sung.com, sw0312.kim@...sung.com,
	kyungmin.park@...sung.com, airlied@...ux.ie, kgene@...nel.org,
	dri-devel@...ts.freedesktop.org, linux-samsung-soc@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm/exynos: Check for NULL dereference of crtc

On 2015년 03월 06일 23:04, Charles Keepax wrote:
> On Fri, Mar 06, 2015 at 10:13:42PM +0900, Inki Dae wrote:
>> On 2015년 02월 18일 02:14, Charles Keepax wrote:
>>> The commit "drm/exynos: remove exynos_plane_dpms" (d9ea6256) removed the
>>> use of the enabled flag, which means that the code may attempt to call
>>> win_enable on a NULL crtc. This results in the following oops on
>>
>> Hmm... it's strange. plane->funcs->destroy() is called prior to
>> crtc->funcs->destroy() so it should be exynos_crtc is not NULL. However,
>> it seems there is any corner case we didn't catch up.
>>
>> Applied.
> 
> Thanks, it seems the offending path in an error path, looks like
> Arndale is missing some required DT setting which causes
> exynos_drm_load to fail:

Right. With quick look, it seems that this issue is incurred because it
tried to access plane->crtc object to call win_disable callback of FIMD
driver before mode_set callback is called: plane->crtc would be set by
mode_set callback so if it has no pair of encoder and crtc then the
plane can never point a crtc object created by FIMD driver.

Thanks,
Inki Dae

> 
> [    1.638109] of_graph_get_next_endpoint(): no port node found in /dp-controller@...B0000
> [    1.646424] exynos-drm exynos-drm: bound 14400000.fimd (ops fimd_component_ops)
> [    1.652704] /dp-controller@...B0000: could not find display-timings node
> [    1.659323] /dp-controller@...B0000: no timings specified
> [    1.664709] [drm:exynos_dp_bind] *ERROR* failed: of_get_videomode() : -22
> [    1.671485] exynos-drm exynos-drm: failed to bind 145b0000.dp-controller (ops exynos_dp_ops): -22
> 
> Which ends up calling exynos_plane_destroy as part of the clean up:
> 
> [    1.698655] [<c0015db4>] (unwind_backtrace) from [<c00121cc>] (show_stack+0x20/0x24)
> [    1.706385] [<c00121cc>] (show_stack) from [<c0528230>] (dump_stack+0x78/0xc4)
> [    1.713588] [<c0528230>] (dump_stack) from [<c02f72ec>] (exynos_disable_plane+0x2c/0x60)
> [    1.721660] [<c02f72ec>] (exynos_disable_plane) from [<c02f733c>] (exynos_plane_destroy+0x1c/0x30)
> [    1.730605] [<c02f733c>] (exynos_plane_destroy) from [<c02e37c4>] (drm_mode_config_cleanup+0x168/0x20c)
> [    1.739982] [<c02e37c4>] (drm_mode_config_cleanup) from [<c02f3d18>] (exynos_drm_load+0xac/0x12c)
> [    1.748832] [<c02f3d18>] (exynos_drm_load) from [<c02dc074>] (drm_dev_register+0xb0/0x110)
> [    1.757075] [<c02dc074>] (drm_dev_register) from [<c02ddc88>] (drm_platform_init+0x50/0xe0)
> [    1.765405] [<c02ddc88>] (drm_platform_init) from [<c02f3a08>] (exynos_drm_bind+0x20/0x28)
> [    1.773655] [<c02f3a08>] (exynos_drm_bind) from [<c02fe664>] (try_to_bring_up_master.part.1+0xd8/0x114)
> [    1.783027] [<c02fe664>] (try_to_bring_up_master.part.1) from [<c02fe754>] (component_master_add_with_match+0xb4/0x134)
> [    1.793792] [<c02fe754>] (component_master_add_with_match) from [<c02f3e94>] (exynos_drm_platform_probe+0xfc/0x124)
> [    1.804207] [<c02f3e94>] (exynos_drm_platform_probe) from [<c0304a44>] (platform_drv_probe+0x58/0xb4)
> [    1.813411] [<c0304a44>] (platform_drv_probe) from [<c0302fa8>] (driver_probe_device+0x11c/0x23c)
> [    1.822261] [<c0302fa8>] (driver_probe_device) from [<c0303164>] (__driver_attach+0x9c/0xa0)
> [    1.830679] [<c0303164>] (__driver_attach) from [<c03014a0>] (bus_for_each_dev+0x64/0x98)
> [    1.838838] [<c03014a0>] (bus_for_each_dev) from [<c0302a4c>] (driver_attach+0x2c/0x30)
> [    1.846824] [<c0302a4c>] (driver_attach) from [<c030269c>] (bus_add_driver+0xe8/0x1e4)
> [    1.854722] [<c030269c>] (bus_add_driver) from [<c0303ad8>] (driver_register+0x88/0x104)
> [    1.862794] [<c0303ad8>] (driver_register) from [<c03048ac>] (__platform_driver_register+0x58/0x6c)
> [    1.871827] [<c03048ac>] (__platform_driver_register) from [<c02f3f84>] (exynos_drm_init+0xc8/0x124)
> [    1.880936] [<c02f3f84>] (exynos_drm_init) from [<c00089f4>] (do_one_initcall+0x90/0x1e0)
> [    1.889096] [<c00089f4>] (do_one_initcall) from [<c08b2e24>] (kernel_init_freeable+0x114/0x1e0)
> [    1.897779] [<c08b2e24>] (kernel_init_freeable) from [<c05235ac>] (kernel_init+0x18/0xfc)
> [    1.905934] [<c05235ac>] (kernel_init) from [<c000efa0>] (ret_from_fork+0x14/0x34)
> 
> Hope that helps some, afraid I am not really familiar enough with
> the graphics stack to chase that down much more though.
> 
> Thanks,
> Charles
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