linux-kernel - Re: [PATCH 06/20] ARM64 / ACPI: Introduce some PCI functions when PCI is enabled

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Date:	Mon, 20 Jan 2014 16:08:01 +0800
From:	Hanjun Guo <hanjun.guo@...aro.org>
To:	Arnd Bergmann <arnd@...db.de>
CC:	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will.deacon@....com>,
	Russell King - ARM Linux <linux@....linux.org.uk>,
	linux-acpi@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	Grant Likely <grant.likely@...aro.org>,
	Matthew Garrett <mjg59@...f.ucam.org>,
	Olof Johansson <olof@...om.net>,
	Linus Walleij <linus.walleij@...aro.org>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Rob Herring <robh@...nel.org>,
	Mark Rutland <mark.rutland@....com>, patches@...aro.org,
	linux-kernel@...r.kernel.org, linaro-kernel@...ts.linaro.org,
	linaro-acpi@...ts.linaro.org, Charles.Garcia-Tobin@....com
Subject: Re: [PATCH 06/20] ARM64 / ACPI: Introduce some PCI functions when
 PCI is enabled

On 2014-1-17 22:04, Arnd Bergmann wrote:
> On Friday 17 January 2014, Hanjun Guo wrote:
>> +++ b/arch/arm64/pci/Makefile
>> @@ -0,0 +1 @@
>> +obj-y                 += pci.o
>> diff --git a/arch/arm64/pci/pci.c b/arch/arm64/pci/pci.c
>> new file mode 100644
>> index 0000000..4e46790
>> --- /dev/null
>> +++ b/arch/arm64/pci/pci.c
>> @@ -0,0 +1,33 @@
>> +#include <linux/acpi.h>
>> +#include <linux/types.h>
>> +#include <linux/kernel.h>
>> +#include <linux/pci.h>
>> +
>> +/**
>> + * raw_pci_read - Platform-specific PCI config space access.
>> + *
>> + * Default empty implementation.  Replace with an architecture-specific setup
>> + * routine, if necessary.
>> + */
>> +int __weak raw_pci_read(unsigned int domain, unsigned int bus,
>> +			unsigned int devfn, int reg, int len, u32 *val)
>> +{
>> +	return -EINVAL;
>> +}
>> +
>> +int __weak raw_pci_write(unsigned int domain, unsigned int bus,
>> +			unsigned int devfn, int reg, int len, u32 val)
>> +{
>> +	return -EINVAL;
>> +}
> 
> I'd rather not see __weak functions here. Just provide them unconditionally
> so that we can add a proper implementation when needed. You could also
> define these as 'static inline' in a header file to keep them from consuming
> space in the object code.

Ok, I will remove __weak in next version.

> 
>> diff --git a/drivers/acpi/plat/arm-core.c b/drivers/acpi/plat/arm-core.c
>> index 3c8521d..1835b21 100644
>> --- a/drivers/acpi/plat/arm-core.c
>> +++ b/drivers/acpi/plat/arm-core.c
>> @@ -100,6 +100,25 @@ int acpi_gsi_to_irq(u32 gsi, unsigned int *irq)
>>  }
>>  EXPORT_SYMBOL_GPL(acpi_gsi_to_irq);
>>  
>> +int acpi_isa_irq_to_gsi(unsigned isa_irq, u32 *gsi)
>> +{
>> +	return -1;
>> +}
>> +
>> +int acpi_register_ioapic(acpi_handle handle, u64 phys_addr, u32 gsi_base)
>> +{
>> +	/* TBD */
>> +	return -EINVAL;
>> +}
>> +EXPORT_SYMBOL(acpi_register_ioapic);
>> +
>> +int acpi_unregister_ioapic(acpi_handle handle, u32 gsi_base)
>> +{
>> +	/* TBD */
>> +	return -EINVAL;
>> +}
>> +EXPORT_SYMBOL(acpi_unregister_ioapic);
>> +
> 
> My feeling is that these are better handled in the ACPI code by not
> calling them on architectures that have no ISA or no IOAPIC support.
> 
> We have configuration symbols for both, so you don't have to make
> it depend on CONFIG_ARM64 or CONFIG_X86.

Do you mean introduce a stub function when there is no ISA support?

acpi_register_ioapic()/acpi_unregister_ioapic() will be used for IOAPIC
hotplug and GIC distributor is something like IOAPIC on x86, so I think
these two functions can be reserved for future use.

Thanks
Hanjun
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