[PATCH v4 7/9] video/aperture: Only remove sysfb on the default vga pci device

[Thomas Zimmermann]

From: Daniel Vetter <daniel.vetter at ffwll.ch>

Instead of calling aperture_remove_conflicting_devices() to remove the
conflicting devices, just call to aperture_detach_devices() to detach
the device that matches the same PCI BAR / aperture range. Since the
former is just a wrapper of the latter plus a sysfb_disable() call,
and now that's done in this function but only for the primary devices.

This fixes a regression introduced by commit ee7a69aa38d8 ("fbdev:
Disable sysfb device registration when removing conflicting FBs"),
where we remove the sysfb when loading a driver for an unrelated pci
device, resulting in the user losing their efifb console or similar.

Note that in practice this only is a problem with the nvidia blob,
because that's the only gpu driver people might install which does not
come with an fbdev driver of it's own. For everyone else the real gpu
driver will restore a working console.

Also note that in the referenced bug there's confusion that this same
bug also happens on amdgpu. But that was just another amdgpu specific
regression, which just happened to happen at roughly the same time and
with the same user-observable symptoms. That bug is fixed now, see
https://bugzilla.kernel.org/show_bug.cgi?id=216331#c15

Note that we should not have any such issues on non-pci multi-gpu
issues, because I could only find two such cases:
- SoC with some external panel over spi or similar. These panel
  drivers do not use drm_aperture_remove_conflicting_framebuffers(),
  so no problem.
- vga+mga, which is a direct console driver and entirely bypasses all
  this.

For the above reasons the cc: stable is just notionally, this patch
will need a backport and that's up to nvidia if they care enough.

v2:
- Explain a bit better why other multi-gpu that aren't pci shouldn't
  have any issues with making all this fully pci specific.

v3
- polish commit message (Javier)

v4:
- Fix commit message style (i.e., commit 1234 ("..."))
- fix Daniel's S-o-b address

Fixes: ee7a69aa38d8 ("fbdev: Disable sysfb device registration when removing conflicting FBs")
Tested-by: Aaron Plattner <aplattner at nvidia.com>
Reviewed-by: Javier Martinez Canillas <javierm at redhat.com>
Link: https://bugzilla.kernel.org/show_bug.cgi?id=216303#c28
Signed-off-by: Daniel Vetter <daniel.vetter at ffwll.ch>
Cc: Aaron Plattner <aplattner at nvidia.com>
Cc: Javier Martinez Canillas <javierm at redhat.com>
Cc: Thomas Zimmermann <tzimmermann at suse.de>
Cc: Helge Deller <deller at gmx.de>
Cc: Sam Ravnborg <sam at ravnborg.org>
Cc: Alex Deucher <alexander.deucher at amd.com>
Cc: <stable at vger.kernel.org> # v5.19+ (if someone else does the backport)
---
 drivers/video/aperture.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/video/aperture.c b/drivers/video/aperture.c
index 1356f0e88241..e4091688b5eb 100644
--- a/drivers/video/aperture.c
+++ b/drivers/video/aperture.c
@@ -322,15 +322,16 @@ int aperture_remove_conflicting_pci_devices(struct pci_dev *pdev, const char *na
 	if (pdev == vga_default_device())
 		primary = true;
 
+	if (primary)
+		sysfb_disable();
+
 	for (bar = 0; bar < PCI_STD_NUM_BARS; ++bar) {
 		if (!(pci_resource_flags(pdev, bar) & IORESOURCE_MEM))
 			continue;
 
 		base = pci_resource_start(pdev, bar);
 		size = pci_resource_len(pdev, bar);
-		ret = aperture_remove_conflicting_devices(base, size, name);
-		if (ret)
-			return ret;
+		aperture_detach_devices(base, size);
 	}
 
 	if (primary) {
-- 
2.40.0