Re: [PATCH v7 06/17] ARM64 / ACPI: Make PCI optional for ACPI on ARM64

Hanjun Guo
2015-01-20T02:39:41Z

On 2015年01月19日 18:42, Catalin Marinas wrote:
> On Sun, Jan 18, 2015 at 06:25:53AM +0000, Hanjun Guo wrote:
>> On 2015年01月16日 17:49, Catalin Marinas wrote:
>>> On Wed, Jan 14, 2015 at 03:04:54PM +0000, Hanjun Guo wrote:
>>>> --- a/arch/arm64/kernel/pci.c
>>>> +++ b/arch/arm64/kernel/pci.c
>>>> @@ -10,6 +10,7 @@
>>>> *
>>>> */
>>>>
>>>> +#include <linux/acpi.h>
>>>> #include <linux/init.h>
>>>> #include <linux/io.h>
>>>> #include <linux/kernel.h>
>>>> @@ -68,3 +69,30 @@ void pci_bus_assign_domain_nr(struct pci_bus *bus, struct device *parent)
>>>> bus->domain_nr = domain;
>>>> }
>>>> #endif
>>>> +
>>>> +/*
>>>> + * raw_pci_read/write - Platform-specific PCI config space access.
>>>> + *
>>>> + * Default empty implementation. Replace with an architecture-specific setup
>>>> + * routine, if necessary.
>>>> + */
>>>> +int raw_pci_read(unsigned int domain, unsigned int bus,
>>>> + unsigned int devfn, int reg, int len, u32 *val)
>>>> +{
>>>> + return -EINVAL;
>>>> +}
>>>> +
>>>> +int raw_pci_write(unsigned int domain, unsigned int bus,
>>>> + unsigned int devfn, int reg, int len, u32 val)
>>>> +{
>>>> + return -EINVAL;
>>>> +}
>>>> +
>>>> +#ifdef CONFIG_ACPI
>>>> +/* Root bridge scanning */
>>>> +struct pci_bus *pci_acpi_scan_root(struct acpi_pci_root *root)
>>>> +{
>>>> + /* TODO: Should be revisited when implementing PCI on ACPI */
>>>> + return NULL;
>>>> +}
>>>> +#endif
> [...]
>>> When PCI is enabled and the above functions are compiled in, do they
>>> need to return any useful data or just -EINVAL. Are they ever called?
>>
>> They will be called if PCI root bridge is defined in DSDT, should I
>> print some warning message before it is implemented?
>
> My point: do they need to return real data when a PCI root bridge is
> defined in DSDT or you always expect them to always return some -E*? Can
> you explain why?

Not always return -E* or NULL;

For raw_pci_read/write(), they are needed to access the PCI config space
before the PCI root bus is created. so they will return 0 if access to
PCI config space is ok; pci_acpi_scan_root() will return root bus
pointer if it is successfully created.

Thanks
Hanjun
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