| Message ID | 20170719012839.20124-2-dja@axtens.net (mailing list archive) |
|---|---|
| State | New, archived |
| Delegated to: | Bjorn Helgaas |
| Headers | show |
On Wed, 2017-07-19 at 11:28 +1000, Daniel Axtens wrote: > Some powerpc devices provide a PCI display that isn't picked up by > the VGA arbiter, presumably because it doesn't support the PCI > legacy VGA ranges. > > Commit c2e1d84523ad ("powerpc: Set default VGA device") introduced > an arch quirk to mark these devices as default to fix X autoconfig. > > The commit message stated that the patch: > > Ensures a default VGA is always set if a graphics adapter is present, > even if firmware did not initialize it. If more than one graphics > adapter is present, ensure the one initialized by firmware is set > as the default VGA device. > > The patch used the following test to decide whether or not to mark > a device as default: > > pci_read_config_word(pdev, PCI_COMMAND, &cmd); > if ((cmd & (PCI_COMMAND_IO | PCI_COMMAND_MEMORY)) || !vga_default_device()) > vga_set_default_device(pdev); > > This doesn't seem like it works quite as intended. Because of the > logical OR, the default device will be set in 2 cases: > > 1) if there is no default device > OR > 2) if this device has normal memory/IO decoding turned on > > This will work as intended if there is only one device, but if > there are multiple devices, we may override the device the VGA > arbiter picked. > > Instead, set a device as default if there is no default device AND > this device decodes. > > This will not change behaviour on single-headed systems. Ack. > Cc: Brian King <brking@linux.vnet.ibm.com> > Signed-off-by: Daniel Axtens <dja@axtens.net> > > --- > > Tested in TCG (the card provided by qemu doesn't automatically > register with vgaarb, so the relevant code path has been tested) > but I would appreciate any tests on real hardware. > --- > arch/powerpc/kernel/pci-common.c | 5 ++++- > 1 file changed, 4 insertions(+), 1 deletion(-) > > diff --git a/arch/powerpc/kernel/pci-common.c b/arch/powerpc/kernel/pci-common.c > index 341a7469cab8..c95fdda3a2dc 100644 > --- a/arch/powerpc/kernel/pci-common.c > +++ b/arch/powerpc/kernel/pci-common.c > @@ -1746,8 +1746,11 @@ static void fixup_vga(struct pci_dev *pdev) > { > u16 cmd; > > + if (vga_default_device()) > + return; > + > pci_read_config_word(pdev, PCI_COMMAND, &cmd); > - if ((cmd & (PCI_COMMAND_IO | PCI_COMMAND_MEMORY)) || !vga_default_device()) > + if (cmd & (PCI_COMMAND_IO | PCI_COMMAND_MEMORY)) > vga_set_default_device(pdev); > > }
diff --git a/arch/powerpc/kernel/pci-common.c b/arch/powerpc/kernel/pci-common.c index 341a7469cab8..c95fdda3a2dc 100644 --- a/arch/powerpc/kernel/pci-common.c +++ b/arch/powerpc/kernel/pci-common.c @@ -1746,8 +1746,11 @@ static void fixup_vga(struct pci_dev *pdev) { u16 cmd; + if (vga_default_device()) + return; + pci_read_config_word(pdev, PCI_COMMAND, &cmd); - if ((cmd & (PCI_COMMAND_IO | PCI_COMMAND_MEMORY)) || !vga_default_device()) + if (cmd & (PCI_COMMAND_IO | PCI_COMMAND_MEMORY)) vga_set_default_device(pdev); }
Some powerpc devices provide a PCI display that isn't picked up by the VGA arbiter, presumably because it doesn't support the PCI legacy VGA ranges. Commit c2e1d84523ad ("powerpc: Set default VGA device") introduced an arch quirk to mark these devices as default to fix X autoconfig. The commit message stated that the patch: Ensures a default VGA is always set if a graphics adapter is present, even if firmware did not initialize it. If more than one graphics adapter is present, ensure the one initialized by firmware is set as the default VGA device. The patch used the following test to decide whether or not to mark a device as default: pci_read_config_word(pdev, PCI_COMMAND, &cmd); if ((cmd & (PCI_COMMAND_IO | PCI_COMMAND_MEMORY)) || !vga_default_device()) vga_set_default_device(pdev); This doesn't seem like it works quite as intended. Because of the logical OR, the default device will be set in 2 cases: 1) if there is no default device OR 2) if this device has normal memory/IO decoding turned on This will work as intended if there is only one device, but if there are multiple devices, we may override the device the VGA arbiter picked. Instead, set a device as default if there is no default device AND this device decodes. This will not change behaviour on single-headed systems. Cc: Brian King <brking@linux.vnet.ibm.com> Signed-off-by: Daniel Axtens <dja@axtens.net> --- Tested in TCG (the card provided by qemu doesn't automatically register with vgaarb, so the relevant code path has been tested) but I would appreciate any tests on real hardware. --- arch/powerpc/kernel/pci-common.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-)