Re: [PATCH 1/2 v2] x86, ia64: Move EFI_FB vga_default_device() initialization to pci_vga_fixup()

["Bruno Prémont" <bonbons@linux-vserver.org>]

On Sun, 10 August 2014 Andreas Noever <andreas.noever@gmail.com> wrote:

> On Sun, Aug 10, 2014 at 2:21 AM, Andreas Noever
> <andreas.noever@gmail.com> wrote:
> > On Sat, Jul 5, 2014 at 7:15 PM, Bjorn Helgaas <bhelgaas@google.com> wrote:
> >> On Wed, Jun 25, 2014 at 12:55:01AM +0200, Bruno Prémont wrote:
> >>> With commit b4aa0163056b ("efifb: Implement vga_default_device() (v2)")
> >>> Matthew Garrett introduced a efifb vga_default_device() so that EFI
> >>> systems that do not load shadow VBIOS or setup VGA get proper value for
> >>> boot_vga PCI sysfs attribute on the corresponding PCI device.
> >>>
> >>> Xorg is refusing to detect devices when boot_vga=0 which is the case on
> >>> some EFI system (e.g. MacBookAir2,1). Xorg detects the GPU and finds
> >>> the dri device but then bails out with "no devices detected".
> >>>
> >>> Note: When vga_default_device() is set boot_vga PCI sysfs attribute
> >>> reflects its state. When unset this attribute is 1 whenever
> >>> IORESOURCE_ROM_SHADOW flag is set.
> >>>
> >>> With introduction of sysfb/simplefb/simpledrm efifb is getting obsolete
> >>> while having native drivers for the GPU also makes selecting
> >>> sysfb/efifb optional.
> >>>
> >>> Remove the efifb implementation of vga_default_device() and initialize
> >>> vgaarb's vga_default_device() with the PCI GPU that matches boot
> >>> screen_info in pci_fixup_video().
> >>>
> >>> Tested-by: Anibal Francisco Martinez Cortina <linuxkid.zeuz@gmail.com>
> >>> Cc: Matthew Garrett <matthew.garrett@nebula.com>
> >>> Cc: stable@vger.kernel.org
> >>> Signed-off-by: Bruno Prémont <bonbons@linux-vserver.org>
> >>
> >> I applied both with Matthew's ack to pci/misc for v3.17, thanks!
> >
> > I just tried to run the latest kernel.  It failed to boot and git
> > bisect points to this commit (MacBookPro10,1 with Nvidia&Intel
> > graphics).
> >
> > The (now removed) code in efifb_setup did always set default_vga, even
> > if it had already been set earlier. The new code in pci_fixup_video
> > runs only if vga_default_device() is NULL. Removing the check fixes
> > the regression.
> >
> >
> > The following calls to vga_set_default_device are made during boot:
> >
> > vga_arbiter_add_pci_device -> vga_set_default_device(intel)
> > pci_fixup_video -> vga_set_default_device(intel) (there are two calls
> > in pci_fixup_video, this one is the one near "Boot video device")
> > pci_fixup_video -> vga_set_default_device(nvidia) (from the "Does
> > firmware framebuffer belong to us?" loop, only if I remove the check)
> >
> > vga_arbiter_add_pci_device chooses intel simply because it is the
> > first device. Next pci_fixup_video(intel) sees that it is the default
> > device, sets the IORESOURCE_ROM_SHADOW flag and calls
> > vga_set_default_device again. And finally (if the check is removed)
> > pci_fixup_video(nvidia) sees that it owns the framebuffer and sets
> > itself as the default device which allows the system to boot again.
> >
> > Does setting the ROM_SHADOW flag on (possibly) the wrong device have
> > any effect?
> Yes it does. Removing the line changes a long standing
> i915 0000:00:02.0: Invalid ROM contents
> into a
> i915 0000:00:02.0: BAR 6: can't assign [??? 0x00000000 flags
> 0x20000000] (bogus alignment).
> 
> The first is logged at KERN_ERR and the second one only at KERN_INFO.
> We are making progress.

How does your system behave if you change vga_arbiter_add_pci_device()
not to set vga_set_default_device() with the first device registered?

That is remove the 
#ifndef __ARCH_HAS_VGA_DEFAULT_DEVICE
code block in vga_arbiter_add_pci_device().

How did your system behave in the past if you did not enable efifb?

Bruno