| Message ID | 20210714102737.198432-4-boqun.feng@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | PCI: hv: Support host bridge probing on ARM64 | expand |
On Wed, Jul 14, 2021 at 06:27:33PM +0800, Boqun Feng wrote: > Currently at root bridge preparation, the corresponding ACPI device will > be set as the companion, however for a Hyper-V virtual PCI root bridge, > there is no corresponding ACPI device, because a Hyper-V virtual PCI > root bridge is discovered via VMBus rather than ACPI table. In order to > support this, we need to make pcibios_root_bridge_prepare() work with > cfg->parent being NULL. It would be nice to have a hint about why we don't actually need the ACPI companion device in this case. > Signed-off-by: Boqun Feng <boqun.feng@gmail.com> > --- > arch/arm64/kernel/pci.c | 8 +++++++- > 1 file changed, 7 insertions(+), 1 deletion(-) > > diff --git a/arch/arm64/kernel/pci.c b/arch/arm64/kernel/pci.c > index 1006ed2d7c60..3b81ac42bc1f 100644 > --- a/arch/arm64/kernel/pci.c > +++ b/arch/arm64/kernel/pci.c > @@ -84,7 +84,13 @@ int pcibios_root_bridge_prepare(struct pci_host_bridge *bridge) > { > if (!acpi_disabled) { > struct pci_config_window *cfg = bridge->bus->sysdata; > - struct acpi_device *adev = to_acpi_device(cfg->parent); > + /* > + * On Hyper-V there is no corresponding APCI device for a root > + * bridge, therefore ->parent is set as NULL by the driver. And > + * set 'adev` as NULL in this case because there is no proper > + * ACPI device. > + */ > + struct acpi_device *adev = cfg->parent ? to_acpi_device(cfg->parent) : NULL; > struct device *bus_dev = &bridge->bus->dev; > > ACPI_COMPANION_SET(&bridge->dev, adev); s/APCI/ACPI/ above. I think this would be more readable like this: struct pci_config_window *cfg = bridge->bus->sysdata; ... if (acpi_disabled) return 0; /* * On Hyper-V there is no corresponding ACPI device for a root * ... */ cfg = bridge->bus->sysdata; if (!cfg->parent) return 0; adev = to_acpi_device(cfg->parent); bus_dev = &bridge->bus->dev; ACPI_COMPANION_SET(&bridge->dev, adev); ... This could be done in two steps: the first to restructure the code without making any functional change, and a second to return when there's no cfg->parent. If you do it in one step, the patch will be much harder to read. Bjorn
diff --git a/arch/arm64/kernel/pci.c b/arch/arm64/kernel/pci.c index 1006ed2d7c60..3b81ac42bc1f 100644 --- a/arch/arm64/kernel/pci.c +++ b/arch/arm64/kernel/pci.c @@ -84,7 +84,13 @@ int pcibios_root_bridge_prepare(struct pci_host_bridge *bridge) { if (!acpi_disabled) { struct pci_config_window *cfg = bridge->bus->sysdata; - struct acpi_device *adev = to_acpi_device(cfg->parent); + /* + * On Hyper-V there is no corresponding APCI device for a root + * bridge, therefore ->parent is set as NULL by the driver. And + * set 'adev` as NULL in this case because there is no proper + * ACPI device. + */ + struct acpi_device *adev = cfg->parent ? to_acpi_device(cfg->parent) : NULL; struct device *bus_dev = &bridge->bus->dev; ACPI_COMPANION_SET(&bridge->dev, adev);
Currently at root bridge preparation, the corresponding ACPI device will be set as the companion, however for a Hyper-V virtual PCI root bridge, there is no corresponding ACPI device, because a Hyper-V virtual PCI root bridge is discovered via VMBus rather than ACPI table. In order to support this, we need to make pcibios_root_bridge_prepare() work with cfg->parent being NULL. Signed-off-by: Boqun Feng <boqun.feng@gmail.com> --- arch/arm64/kernel/pci.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-)