Hi Ben > -----Original Message----- > From: Benjamin Herrenschmidt [mailto:benh@xxxxxxxxxxxxxxxxxxx] > Sent: 13 July 2017 21:45 > To: Bjorn Helgaas; Gabriele Paoloni > Cc: Daniel Axtens; linux-pci@xxxxxxxxxxxxxxx; Liuxinliang (Matthew > Liu); Rongrong Zou; Catalin Marinas; Will Deacon; linux-arm- > kernel@xxxxxxxxxxxxxxxxxxx; David Airlie; Daniel Vetter; Alex > Williamson > Subject: Re: [PATCH v4] PCI: Support hibmc VGA cards behind a > misbehaving HiSilicon bridge > > On Thu, 2017-07-13 at 06:29 -0500, Bjorn Helgaas wrote: > > > Indeed our host controller depends on ARM64 so maybe it would make > > > sense to move the quirk arch/arm64/kernel/pci.c; however regardless > > > why is it strictly required for a VGA device to be legacy one in > order > > > to make it the default boot device? > > > i.e. couldn't we have: > > > > > > diff --git a/drivers/gpu/vga/vgaarb.c b/drivers/gpu/vga/vgaarb.c > > > index 0f5b2dd..a6b606c 100644 > > > --- a/drivers/gpu/vga/vgaarb.c > > > +++ b/drivers/gpu/vga/vgaarb.c > > > @@ -667,8 +667,7 @@ static bool vga_arbiter_add_pci_device(struct > pci_dev *pdev) > > > /* Deal with VGA default device. Use first enabled one > > > * by default if arch doesn't have it's own hook > > > */ > > > - if (vga_default == NULL && > > > - ((vgadev->owns & VGA_RSRC_LEGACY_MASK) == > VGA_RSRC_LEGACY_MASK)) { > > > + if (vga_default == NULL) { > > > vgaarb_info(&pdev->dev, "setting as boot VGA > device\n"); > > > vga_set_default_device(pdev); > > > } > > > > I don't know enough about the VGA arbiter to answer this. This test > was > > part of the initial implementation: deb2d2ecd43d ("PCI/GPU: implement > VGA > > arbitration on Linux") by Ben. > > The above simply uses the first device that has memory and IO enabled > as the default device (you don't need to have a default device). > > This is essentially picking up whatever device had been initialized > by the BIOS/firmware as default. This is needed for example on x86 > where the BIOS tends to only initialize one device. > > I'm not sure what problem you are trying to solve here ? Well our host platform does not support legacy devices and therefore we find ourselves without a default VGA device... I was trying to understand why a default device has to be legacy...but I think this was answered by both you and Alex in other follows-up... Thanks Gab > > Cheers, > Ben.
