On Tue, Jan 20, 2015 at 12:26:57PM +0000, Tomasz Nowicki wrote:

On 20.01.2015 12:00, Catalin Marinas wrote:

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On Tue, Jan 20, 2015 at 02:39:16AM +0000, Hanjun Guo wrote:

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On 2015?01?19? 18:42, Catalin Marinas wrote:

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On Sun, Jan 18, 2015 at 06:25:53AM +0000, Hanjun Guo wrote:

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On 2015?01?16? 17:49, Catalin Marinas wrote:

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On Wed, Jan 14, 2015 at 03:04:54PM +0000, Hanjun Guo wrote:

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--- 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

[...]

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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.

OK. So what's the plan for implementing these functions properly. For
the raw_pci_read/write, the comment states "replace with an
architecture-specific setup routine". What does this mean?

raw_pci_read/write will use MMCONFIG code to access PCI config space. 
Please see my patch set:
http://lkml.iu.edu/hypermail/linux/kernel/1411.2/02753.html
which is going to refactor the x86 specific code so it would be usable 
for ARM64 too.

OK. Thanks for the information.

-- 
Catalin