From mboxrd@z Thu Jan 1 00:00:00 1970 From: julien.thierry@arm.com (Julien Thierry) Date: Thu, 12 Oct 2017 12:24:10 +0100 Subject: [PATCH 1/2] vgaarb: Select a default VGA device even if there's no legacy VGA In-Reply-To: <20171006222428.12211.3635.stgit@bhelgaas-glaptop.roam.corp.google.com> References: <20171006221358.12211.42879.stgit@bhelgaas-glaptop.roam.corp.google.com> <20171006222428.12211.3635.stgit@bhelgaas-glaptop.roam.corp.google.com> Message-ID: To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org Hi Bjorn, On 06/10/17 23:24, Bjorn Helgaas wrote: > From: Bjorn Helgaas > > Daniel Axtens reported that on the HiSilicon D05 board, the VGA device is > behind a bridge that doesn't support PCI_BRIDGE_CTL_VGA, so the VGA arbiter > never selects it as the default, which means Xorg auto-detection doesn't > work. > > VGA is a legacy PCI feature: a VGA device can respond to addresses, e.g., > [mem 0xa0000-0xbffff], [io 0x3b0-0x3bb], [io 0x3c0-0x3df], etc., that are > not configurable by BARs. Consequently, multiple VGA devices can conflict > with each other. The VGA arbiter avoids conflicts by ensuring that those > legacy resources are only routed to one VGA device at a time. > > The arbiter identifies the "default VGA" device, i.e., a legacy VGA device > that was used by boot firmware. It selects the first device that: > > - is of PCI_CLASS_DISPLAY_VGA, > - has both PCI_COMMAND_IO and PCI_COMMAND_MEMORY enabled, and > - has PCI_BRIDGE_CTL_VGA set in all upstream bridges. > > Some systems don't have such a device. For example, if a host bridge > doesn't support I/O space, PCI_COMMAND_IO probably won't be enabled for any > devices below it. Or, as on the HiSilicon D05, the VGA device may be > behind a bridge that doesn't support PCI_BRIDGE_CTL_VGA, so accesses to the > legacy VGA resources will never reach the device. > > This patch extends the arbiter so that if it doesn't find a device that > meets all the above criteria, it selects the first device that: > > - is of PCI_CLASS_DISPLAY_VGA and > - has PCI_COMMAND_IO or PCI_COMMAND_MEMORY enabled > > If it doesn't find even that, it selects the first device that: > > - is of class PCI_CLASS_DISPLAY_VGA. > > Such a device may not be able to use the legacy VGA resources, but most > drivers can operate the device without those. Setting it as the default > device means its "boot_vga" sysfs file will contain "1", which Xorg (via > libpciaccess) uses to help select its default output device. > > This fixes Xorg auto-detection on some arm64 systems (HiSilicon D05 in > particular; see the link below). > > It also replaces the powerpc fixup_vga() quirk, albeit with slightly > different semantics: the quirk selected the first VGA device we found, and > overrode that selection with any enabled VGA device we found. If there > were several enabled VGA devices, the *last* one we found would become the > default. > > The code here instead selects the *first* enabled VGA device we find, and > if none are enabled, the first VGA device we find. > > Link: http://lkml.kernel.org/r/20170901072744.2409-1-dja at axtens.net > Tested-by: Daniel Axtens # arm64, ppc64-qemu-tcg > Signed-off-by: Bjorn Helgaas > --- > arch/powerpc/kernel/pci-common.c | 12 ------------ > drivers/gpu/vga/vgaarb.c | 25 +++++++++++++++++++++++++ > 2 files changed, 25 insertions(+), 12 deletions(-) > > diff --git a/arch/powerpc/kernel/pci-common.c b/arch/powerpc/kernel/pci-common.c > index 02831a396419..0ac7aa346c69 100644 > --- a/arch/powerpc/kernel/pci-common.c > +++ b/arch/powerpc/kernel/pci-common.c > @@ -1740,15 +1740,3 @@ static void fixup_hide_host_resource_fsl(struct pci_dev *dev) > } > DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_MOTOROLA, PCI_ANY_ID, fixup_hide_host_resource_fsl); > DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_FREESCALE, PCI_ANY_ID, fixup_hide_host_resource_fsl); > - > -static void fixup_vga(struct pci_dev *pdev) > -{ > - u16 cmd; > - > - pci_read_config_word(pdev, PCI_COMMAND, &cmd); > - if ((cmd & (PCI_COMMAND_IO | PCI_COMMAND_MEMORY)) || !vga_default_device()) > - vga_set_default_device(pdev); > - > -} > -DECLARE_PCI_FIXUP_CLASS_FINAL(PCI_ANY_ID, PCI_ANY_ID, > - PCI_CLASS_DISPLAY_VGA, 8, fixup_vga); > diff --git a/drivers/gpu/vga/vgaarb.c b/drivers/gpu/vga/vgaarb.c > index 76875f6299b8..aeb41f793ed4 100644 > --- a/drivers/gpu/vga/vgaarb.c > +++ b/drivers/gpu/vga/vgaarb.c > @@ -1468,6 +1468,31 @@ static int __init vga_arb_device_init(void) > vgaarb_info(dev, "no bridge control possible\n"); > } > > + if (!vga_default_device()) { > + list_for_each_entry(vgadev, &vga_list, list) { > + struct device *dev = &vgadev->pdev->dev; > + u16 cmd; > + > + pdev = vgadev->pdev; > + pci_read_config_word(pdev, PCI_COMMAND, &cmd); > + if (cmd & (PCI_COMMAND_IO | PCI_COMMAND_MEMORY)) { > + vgaarb_info(dev, "setting as boot device (VGA legacy resources not available)\n"); > + vga_set_default_device(pdev); > + break; > + } > + } > + } > + > + if (!vga_default_device()) { > + vgadev = list_first_entry_or_null(&vga_list, > + struct vga_device, list); > + if (vgadev) { > + struct device *dev = &vgadev->pdev->dev; > + vgaarb_info(dev, "setting as boot device (VGA legacy resources not available)\n"); > + vga_set_default_device(pdev); Isn't 'pdev' NULL here? shouldn't it be vgadev->pdev instead? Cheers, -- Julien Thierry