From: Bjorn Helgaas <helgaas@kernel.org> To: Boqun Feng <boqun.feng@gmail.com> Cc: "Bjorn Helgaas" <bhelgaas@google.com>, "Arnd Bergmann" <arnd@arndb.de>, "Marc Zyngier" <maz@kernel.org>, "Catalin Marinas" <catalin.marinas@arm.com>, "Will Deacon" <will@kernel.org>, "K. Y. Srinivasan" <kys@microsoft.com>, "Haiyang Zhang" <haiyangz@microsoft.com>, "Stephen Hemminger" <sthemmin@microsoft.com>, "Wei Liu" <wei.liu@kernel.org>, "Dexuan Cui" <decui@microsoft.com>, "Lorenzo Pieralisi" <lorenzo.pieralisi@arm.com>, "Rob Herring" <robh@kernel.org>, "Krzysztof Wilczyński" <kw@linux.com>, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-hyperv@vger.kernel.org, linux-pci@vger.kernel.org, "Sunil Muthuswamy" <sunilmut@microsoft.com>, "Mike Rapoport" <rppt@kernel.org> Subject: Re: [RFC v4 3/7] arm64: PCI: Support root bridge preparation for Hyper-V PCI Date: Wed, 14 Jul 2021 14:46:45 -0500 [thread overview] Message-ID: <20210714194645.GA1869525@bjorn-Precision-5520> (raw) In-Reply-To: <20210714102737.198432-4-boqun.feng@gmail.com> 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
WARNING: multiple messages have this Message-ID (diff)
From: Bjorn Helgaas <helgaas@kernel.org> To: Boqun Feng <boqun.feng@gmail.com> Cc: "Bjorn Helgaas" <bhelgaas@google.com>, "Arnd Bergmann" <arnd@arndb.de>, "Marc Zyngier" <maz@kernel.org>, "Catalin Marinas" <catalin.marinas@arm.com>, "Will Deacon" <will@kernel.org>, "K. Y. Srinivasan" <kys@microsoft.com>, "Haiyang Zhang" <haiyangz@microsoft.com>, "Stephen Hemminger" <sthemmin@microsoft.com>, "Wei Liu" <wei.liu@kernel.org>, "Dexuan Cui" <decui@microsoft.com>, "Lorenzo Pieralisi" <lorenzo.pieralisi@arm.com>, "Rob Herring" <robh@kernel.org>, "Krzysztof Wilczyński" <kw@linux.com>, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-hyperv@vger.kernel.org, linux-pci@vger.kernel.org, "Sunil Muthuswamy" <sunilmut@microsoft.com>, "Mike Rapoport" <rppt@kernel.org> Subject: Re: [RFC v4 3/7] arm64: PCI: Support root bridge preparation for Hyper-V PCI Date: Wed, 14 Jul 2021 14:46:45 -0500 [thread overview] Message-ID: <20210714194645.GA1869525@bjorn-Precision-5520> (raw) In-Reply-To: <20210714102737.198432-4-boqun.feng@gmail.com> 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 _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next prev parent reply other threads:[~2021-07-14 19:53 UTC|newest] Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-07-14 10:27 [RFC v4 0/7] PCI: hv: Support host bridge probing on ARM64 Boqun Feng 2021-07-14 10:27 ` Boqun Feng 2021-07-14 10:27 ` [RFC v4 1/7] PCI: Introduce domain_nr in pci_host_bridge Boqun Feng 2021-07-14 10:27 ` Boqun Feng 2021-07-14 19:33 ` Bjorn Helgaas 2021-07-14 19:33 ` Bjorn Helgaas 2021-07-15 17:30 ` Boqun Feng 2021-07-15 17:30 ` Boqun Feng 2021-07-15 19:07 ` Bjorn Helgaas 2021-07-15 19:07 ` Bjorn Helgaas 2021-07-15 19:11 ` Arnd Bergmann 2021-07-15 19:11 ` Arnd Bergmann 2021-07-14 10:27 ` [RFC v4 2/7] PCI: Allow msi domain set-up at host probing time Boqun Feng 2021-07-14 10:27 ` Boqun Feng 2021-07-14 19:39 ` Bjorn Helgaas 2021-07-14 19:39 ` Bjorn Helgaas 2021-07-14 10:27 ` [RFC v4 3/7] arm64: PCI: Support root bridge preparation for Hyper-V PCI Boqun Feng 2021-07-14 10:27 ` Boqun Feng 2021-07-14 19:46 ` Bjorn Helgaas [this message] 2021-07-14 19:46 ` Bjorn Helgaas 2021-07-14 10:27 ` [RFC v4 4/7] PCI: hv: Generify PCI probing Boqun Feng 2021-07-14 10:27 ` Boqun Feng 2021-07-14 19:49 ` Bjorn Helgaas 2021-07-14 19:49 ` Bjorn Helgaas 2021-07-14 10:27 ` [RFC v4 5/7] PCI: hv: Use pci_host_bridge::domain_nr for PCI domain Boqun Feng 2021-07-14 10:27 ` Boqun Feng 2021-07-14 17:04 ` [EXTERNAL] " Sunil Muthuswamy 2021-07-14 17:04 ` Sunil Muthuswamy 2021-07-15 3:59 ` Boqun Feng 2021-07-15 3:59 ` Boqun Feng 2021-07-14 10:27 ` [RFC v4 6/7] PCI: hv: Set up msi domain at bridge probing time Boqun Feng 2021-07-14 10:27 ` Boqun Feng 2021-07-14 10:27 ` [RFC v4 7/7] PCI: hv: Turn on the host bridge probing on ARM64 Boqun Feng 2021-07-14 10:27 ` Boqun Feng
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