[PATCH v4] PCI: Support hibmc VGA cards behind a misbehaving HiSilicon bridge

[Bjorn Helgaas]

[+cc Ben, David, Daniel, Alex]

On Thu, Jul 13, 2017 at 10:29:25AM +0000, Gabriele Paoloni wrote:
> Hi Bjorn, Daniel
> 
> [...]
> 
> > 
> > Is this quirk useful on any arch other than arm64?  Per
> > drivers/pci/dwc/Kconfig, CONFIG_PCI_HISI depends on CONFIG_ARM64.
> > 
> > Would it make sense to put this quirk in arch/arm64/kernel/pci.c?
> 
> 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.

Bjorn