[L] [PATCH 2/9] video/aperture: use generic code to figure out the vga default device

Kai-Heng Feng kai.heng.feng at canonical.com
Wed Jul 26 08:19:40 UTC 2023


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

BugLink: https://bugs.launchpad.net/bugs/2028749

Since vgaarb has been promoted to be a core piece of the pci subsystem
we don't have to open code random guesses anymore, we actually know
this in a platform agnostic way, and there's no need for an x86
specific hack. See also commit 1d38fe6ee6a8 ("PCI/VGA: Move vgaarb to
drivers/pci")

This should not result in any functional change, and the non-x86
multi-gpu pci systems are probably rare enough to not matter (I don't
know of any tbh). But it's a nice cleanup, so let's do it.

There's been a few questions on previous iterations on dri-devel and
irc:

- fb_is_primary_device() seems to be yet another implementation of
  this theme, and at least on x86 it checks for both
  vga_default_device OR rom shadowing. There shouldn't ever be a case
  where rom shadowing gives any additional hints about the boot vga
  device, but if there is then the default vga selection in vgaarb
  should probably be fixed. And not special-case checks replicated all
  over.

- Thomas also brought up that on most !x86 systems
  fb_is_primary_device() returns 0, except on sparc/parisc. But these
  2 special cases are about platform specific devices and not pci, so
  shouldn't have any interactions.

- Furthermore fb_is_primary_device() is a bit a red herring since it's
  only used to select the right fbdev driver for fbcon, and not for
  the fw handover dance which the aperture helpers handle. At least
  for x86 we might want to look into unifying them, but that's a
  separate thing.

v2: Extend commit message trying to summarize various discussions.

v4:
- make the test for the primary device easier to read (Javier)
- fix commit message style (i.e., commit 1234 ("..."))
- fix Daniel's S-o-b address

v5:
- add back an S-o-b tag with Daniel's Intel address

Signed-off-by: Daniel Vetter <daniel.vetter at ffwll.ch>
Signed-off-by: Daniel Vetter <daniel.vetter at intel.com>
Signed-off-by: Thomas Zimmermann <tzimmermann at suse.de>
Cc: Thomas Zimmermann <tzimmermann at suse.de>
Cc: Javier Martinez Canillas <javierm at redhat.com>
Cc: Helge Deller <deller at gmx.de>
Cc: linux-fbdev at vger.kernel.org
Cc: Bjorn Helgaas <bhelgaas at google.com>
Cc: linux-pci at vger.kernel.org
Reviewed-by: Javier Martinez Canillas <javierm at redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230406132109.32050-3-tzimmermann@suse.de
(cherry picked from commit db082219569e3392cd38c9e322151450c855eed4)
Signed-off-by: Kai-Heng Feng <kai.heng.feng at canonical.com>
---
 drivers/video/aperture.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/drivers/video/aperture.c b/drivers/video/aperture.c
index 41e77de1ea82..d0eccc4ed60b 100644
--- a/drivers/video/aperture.c
+++ b/drivers/video/aperture.c
@@ -328,9 +328,8 @@ int aperture_remove_conflicting_pci_devices(struct pci_dev *pdev, const char *na
 	resource_size_t base, size;
 	int bar, ret;
 
-#ifdef CONFIG_X86
-	primary = pdev->resource[PCI_ROM_RESOURCE].flags & IORESOURCE_ROM_SHADOW;
-#endif
+	if (pdev == vga_default_device())
+		primary = true;
 
 	for (bar = 0; bar < PCI_STD_NUM_BARS; ++bar) {
 		if (!(pci_resource_flags(pdev, bar) & IORESOURCE_MEM))
-- 
2.34.1




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