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

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Message-ID: <20150119104240.GE11835@e104818-lin.cambridge.arm.com>
Date:	Mon, 19 Jan 2015 10:42:40 +0000
From:	Catalin Marinas <catalin.marinas@....com>
To:	Hanjun Guo <hanjun.guo@...aro.org>
Cc:	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Olof Johansson <olof@...om.net>, Arnd Bergmann <arnd@...db.de>,
	Mark Rutland <Mark.Rutland@....com>,
	"grant.likely@...aro.org" <grant.likely@...aro.org>,
	Will Deacon <Will.Deacon@....com>,
	Lorenzo Pieralisi <Lorenzo.Pieralisi@....com>,
	"graeme.gregory@...aro.org" <graeme.gregory@...aro.org>,
	Sudeep Holla <Sudeep.Holla@....com>,
	"jcm@...hat.com" <jcm@...hat.com>,
	Jason Cooper <jason@...edaemon.net>,
	Marc Zyngier <Marc.Zyngier@....com>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Mark Brown <broonie@...nel.org>, Rob Herring <robh@...nel.org>,
	Robert Richter <rric@...nel.org>,
	Randy Dunlap <rdunlap@...radead.org>,
	Charles Garcia-Tobin <Charles.Garcia-Tobin@....com>,
	"phoenix.liyi@...wei.com" <phoenix.liyi@...wei.com>,
	Timur Tabi <timur@...eaurora.org>,
	"suravee.suthikulpanit@....com" <suravee.suthikulpanit@....com>,
	"wangyijing@...wei.com" <wangyijing@...wei.com>,
	"linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linaro-acpi@...ts.linaro.org" <linaro-acpi@...ts.linaro.org>
Subject: Re: [PATCH v7 06/17] ARM64 / ACPI: Make PCI optional for ACPI on
 ARM64

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?

-- 
Catalin
--
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