linux-kernel - Re: [PATCH V9 10/11] ARM64/PCI: Implement ACPI low-level calls to access PCI

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Date:	Fri, 10 Jun 2016 21:54:23 +0100
From:	Lorenzo Pieralisi <lorenzo.pieralisi@....com>
To:	Tomasz Nowicki <tn@...ihalf.com>
Cc:	helgaas@...nel.org, arnd@...db.de, will.deacon@....com,
	catalin.marinas@....com, rafael@...nel.org, hanjun.guo@...aro.org,
	okaya@...eaurora.org, jchandra@...adcom.com,
	robert.richter@...iumnetworks.com, mw@...ihalf.com,
	Liviu.Dudau@....com, ddaney@...iumnetworks.com,
	wangyijing@...wei.com, Suravee.Suthikulpanit@....com,
	msalter@...hat.com, linux-pci@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-acpi@...r.kernel.org,
	linux-kernel@...r.kernel.org, linaro-acpi@...ts.linaro.org,
	jcm@...hat.com, andrea.gallo@...aro.org, dhdang@....com,
	jeremy.linton@....com, liudongdong3@...wei.com, cov@...eaurora.org
Subject: Re: [PATCH V9 10/11] ARM64/PCI: Implement ACPI low-level calls to
 access PCI_Config region from AML

On Fri, Jun 10, 2016 at 09:55:18PM +0200, Tomasz Nowicki wrote:
> ACPI spec6.1 - chapter: 5.5.2.4 defines OperationRegion (Declare Operation
> Region). Following the spec: " [...] An Operation Region is a specific
> region of operation within an address space that is declared as a subset
> of the entire address space using a starting address (offset) and a length.
> Control methods must have exclusive access to any address accessed via
> fields declared in Operation Regions. [...]".
> 
> OperationRegion allows to declare various of operation region address space

s/of//

> identifiers including PCI_Config. PCI_Config is meant to access PCI
> configuration space from the ASL. So every time ASL opcode operates
> on PCI_Config space region, ASL interpreter dispatches accesses to OS
> low-level calls - raw_pci_write() and raw_pci_read() for Linux - so-called
> ACPI RAW accessors.
> 
> In order to support PCI_Config operation region, implement mentioned
> raw_pci_write() and raw_pci_read() calls so they find associated bus
> and call read/write ops.
> 
> Waiting for clarification in the ACPI specifications in relation
> to PCI_Config space handling before PCI bus enumeration is completed,
> current code does not support PCI_Config region accesses before PCI bus
> enumeration whilst providing full AML PCI_Config access availability
> when the PCI bus enumeration is completed by the kernel so that
> RAW accessors can look-up PCI operations through the struct pci_bus
> associated with a PCI bus.
> 
> Signed-off-by: Tomasz Nowicki <tn@...ihalf.com>
> Signed-off-by: Jayachandran C <jchandra@...adcom.com>

Reviewed-by: Lorenzo Pieralisi <lorenzo.pieralisi@....com>

> ---
>  arch/arm64/kernel/pci.c | 12 ++++++++++--
>  1 file changed, 10 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/arm64/kernel/pci.c b/arch/arm64/kernel/pci.c
> index b3b8a2c..328f857 100644
> --- a/arch/arm64/kernel/pci.c
> +++ b/arch/arm64/kernel/pci.c
> @@ -71,13 +71,21 @@ int pcibios_alloc_irq(struct pci_dev *dev)
>  int raw_pci_read(unsigned int domain, unsigned int bus,
>  		  unsigned int devfn, int reg, int len, u32 *val)
>  {
> -	return -ENXIO;
> +	struct pci_bus *b = pci_find_bus(domain, bus);
> +
> +	if (!b)
> +		return PCIBIOS_DEVICE_NOT_FOUND;
> +	return b->ops->read(b, devfn, reg, len, val);
>  }
>  
>  int raw_pci_write(unsigned int domain, unsigned int bus,
>  		unsigned int devfn, int reg, int len, u32 val)
>  {
> -	return -ENXIO;
> +	struct pci_bus *b = pci_find_bus(domain, bus);
> +
> +	if (!b)
> +		return PCIBIOS_DEVICE_NOT_FOUND;
> +	return b->ops->write(b, devfn, reg, len, val);
>  }
>  
>  #ifdef CONFIG_NUMA
> -- 
> 1.9.1
>