[PATCH v2] video/aperture: Call sysfb_disable() before removing PCI devices

[Thomas Zimmermann]

Call sysfb_disable() from aperture_remove_conflicting_pci_devices()
before removing PCI devices. Without, simpledrm can still bind to
simple-framebuffer devices after the hardware driver has taken over
the hardware. Both drivers interfere with each other and results are
undefined.

Reported modesetting errors [1] are shown below.

---- snap ----
rcu: INFO: rcu_sched detected expedited stalls on CPUs/tasks: { 13-.... } 7 jiffies s: 165 root: 0x2000/.
rcu: blocking rcu_node structures (internal RCU debug):
Task dump for CPU 13:
task:X               state:R  running task     stack:    0 pid: 4242 ppid:  4228 flags:0x00000008
Call Trace:
 <TASK>
 ? commit_tail+0xd7/0x130
 ? drm_atomic_helper_commit+0x126/0x150
 ? drm_atomic_commit+0xa4/0xe0
 ? drm_plane_get_damage_clips.cold+0x1c/0x1c
 ? drm_atomic_helper_dirtyfb+0x19e/0x280
 ? drm_mode_dirtyfb_ioctl+0x10f/0x1e0
 ? drm_mode_getfb2_ioctl+0x2d0/0x2d0
 ? drm_ioctl_kernel+0xc4/0x150
 ? drm_ioctl+0x246/0x3f0
 ? drm_mode_getfb2_ioctl+0x2d0/0x2d0
 ? __x64_sys_ioctl+0x91/0xd0
 ? do_syscall_64+0x60/0xd0
 ? entry_SYSCALL_64_after_hwframe+0x4b/0xb5
 </TASK>
...
rcu: INFO: rcu_sched detected expedited stalls on CPUs/tasks: { 13-.... } 30 jiffies s: 169 root: 0x2000/.
rcu: blocking rcu_node structures (internal RCU debug):
Task dump for CPU 13:
task:X               state:R  running task     stack:    0 pid: 4242 ppid:  4228 flags:0x0000400e
Call Trace:
 <TASK>
 ? memcpy_toio+0x76/0xc0
 ? memcpy_toio+0x1b/0xc0
 ? drm_fb_memcpy_toio+0x76/0xb0
 ? drm_fb_blit_toio+0x75/0x2b0
 ? simpledrm_simple_display_pipe_update+0x132/0x150
 ? drm_atomic_helper_commit_planes+0xb6/0x230
 ? drm_atomic_helper_commit_tail+0x44/0x80
 ? commit_tail+0xd7/0x130
 ? drm_atomic_helper_commit+0x126/0x150
 ? drm_atomic_commit+0xa4/0xe0
 ? drm_plane_get_damage_clips.cold+0x1c/0x1c
 ? drm_atomic_helper_dirtyfb+0x19e/0x280
 ? drm_mode_dirtyfb_ioctl+0x10f/0x1e0
 ? drm_mode_getfb2_ioctl+0x2d0/0x2d0
 ? drm_ioctl_kernel+0xc4/0x150
 ? drm_ioctl+0x246/0x3f0
 ? drm_mode_getfb2_ioctl+0x2d0/0x2d0
 ? __x64_sys_ioctl+0x91/0xd0
 ? do_syscall_64+0x60/0xd0
 ? entry_SYSCALL_64_after_hwframe+0x4b/0xb5
 </TASK>

The problem was added by commit 5e0137612430 ("video/aperture: Disable
and unregister sysfb devices via aperture helpers") to v6.0.3 and does
not exist in the mainline branch.

The mainline commit 5e0137612430 ("video/aperture: Disable and
unregister sysfb devices via aperture helpers") has been backported
from v6.0-rc1 to stable v6.0.3 from a larger patch series [2] that
reworks fbdev framebuffer ownership. The backport misses a change to
aperture_remove_conflicting_pci_devices(). Mainline itself is fine,
because the function does not exist there as a result of the patch
series.

Instead of backporting the whole series, fix the additional function.

v2:
	* expand justification for this fix (Greg)

Reported-by: Andreas Thalhammer <andreas.thalhammer-linux at gmx.net>
Reported-by: Thorsten Leemhuis <regressions at leemhuis.info>
Signed-off-by: Thomas Zimmermann <tzimmermann at suse.de>
Tested-by: Andreas Thalhammer <andreas.thalhammer-linux at gmx.net>
Fixes: cfecfc98a78d ("video/aperture: Disable and unregister sysfb devices via aperture helpers")
Cc: Thomas Zimmermann <tzimmermann at suse.de>
Cc: Javier Martinez Canillas <javierm at redhat.com>
Cc: Zack Rusin <zackr at vmware.com>
Cc: Daniel Vetter <daniel.vetter at ffwll.ch>
Cc: Daniel Vetter <daniel at ffwll.ch>
Cc: Sam Ravnborg <sam at ravnborg.org>
Cc: Helge Deller <deller at gmx.de>
Cc: Alex Deucher <alexander.deucher at amd.com>
Cc: Zhen Lei <thunder.leizhen at huawei.com>
Cc: Changcheng Deng <deng.changcheng at zte.com.cn>
Cc: Maarten Lankhorst <maarten.lankhorst at linux.intel.com>
Cc: Maxime Ripard <mripard at kernel.org>
Cc: dri-devel at lists.freedesktop.org
Cc: Sasha Levin <sashal at kernel.org>
Cc: linux-fbdev at vger.kernel.org
Cc: <stable at vger.kernel.org> # v6.0.3+
Link: https://lore.kernel.org/dri-devel/d6afe54b-f8d7-beb2-3609-186e566cbfac@gmx.net/T/#t # [1]
Link: https://patchwork.freedesktop.org/series/106040/ # [2]
---
 drivers/video/aperture.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/drivers/video/aperture.c b/drivers/video/aperture.c
index d245826a9324..cc6427a091bc 100644
--- a/drivers/video/aperture.c
+++ b/drivers/video/aperture.c
@@ -338,6 +338,17 @@ int aperture_remove_conflicting_pci_devices(struct pci_dev *pdev, const char *na
 	resource_size_t base, size;
 	int bar, ret;
 
+	/*
+	 * If a driver asked to unregister a platform device registered by
+	 * sysfb, then can be assumed that this is a driver for a display
+	 * that is set up by the system firmware and has a generic driver.
+	 *
+	 * Drivers for devices that don't have a generic driver will never
+	 * ask for this, so let's assume that a real driver for the display
+	 * was already probed and prevent sysfb to register devices later.
+	 */
+	sysfb_disable();
+
 	/*
 	 * WARNING: Apparently we must kick fbdev drivers before vgacon,
 	 * otherwise the vga fbdev driver falls over.
-- 
2.38.0