Originally, cns3xxx used it's own functions for mapping, reading and writing registers.
Commit 802b7c06adc7 ("ARM: cns3xxx: Convert PCI to use generic config accessors") removed the internal PCI config write function in favor of the generic one:
cns3xxx_pci_write_config() --> pci_generic_config_write()
cns3xxx_pci_write_config() expected aligned addresses, being produced by cns3xxx_pci_map_bus() while the generic one pci_generic_config_write() actually expects the real address as both the function and hardware are capable of byte-aligned writes.
This currently leads to pci_generic_config_write() writing to the wrong registers on some ocasions.
First issue seen due to this:
- driver ath9k gets loaded - The driver wants to write value 0xA8 to register PCI_LATENCY_TIMER, located at 0x0D - cns3xxx_pci_map_bus() aligns the address to 0x0C - pci_generic_config_write() effectively writes 0xA8 into register 0x0C (CACHE_LINE_SIZE)
This seems to cause some slight instability when certain PCI devices are used.
Another issue example caused by this this is the PCI bus numbering, where the primary bus is higher than the secondary, which is impossible.
Before:
00:00.0 PCI bridge: Cavium, Inc. Device 3400 (rev 01) (prog-if 00 [Normal decode]) Flags: bus master, fast devsel, latency 0, IRQ 255 Bus: primary=02, secondary=01, subordinate=ff, sec-latency=0
After fix:
00:00.0 PCI bridge: Cavium, Inc. Device 3400 (rev 01) (prog-if 00 [Normal decode]) Flags: bus master, fast devsel, latency 0, IRQ 255 Bus: primary=00, secondary=01, subordinate=02, sec-latency=0
And very likely some more ..
Fix all by omitting the alignment being done in the mapping function.
Fixes: 802b7c06adc7 ("ARM: cns3xxx: Convert PCI to use generic config accessors") Signed-off-by: Koen Vandeputte koen.vandeputte@ncentric.com CC: Arnd Bergmann arnd@arndb.de CC: Bjorn Helgaas bhelgaas@google.com CC: Krzysztof Halasa khalasa@piap.pl CC: Olof Johansson olof@lixom.net CC: Robin Leblon robin.leblon@ncentric.com CC: Rob Herring robh@kernel.org CC: Russell King linux@armlinux.org.uk CC: Tim Harvey tharvey@gateworks.com CC: stable@vger.kernel.org # v4.0+ --- arch/arm/mach-cns3xxx/pcie.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/arm/mach-cns3xxx/pcie.c b/arch/arm/mach-cns3xxx/pcie.c index 318394ed5c7a..5e11ad3164e0 100644 --- a/arch/arm/mach-cns3xxx/pcie.c +++ b/arch/arm/mach-cns3xxx/pcie.c @@ -83,7 +83,7 @@ static void __iomem *cns3xxx_pci_map_bus(struct pci_bus *bus, } else /* remote PCI bus */ base = cnspci->cfg1_regs + ((busno & 0xf) << 20);
- return base + (where & 0xffc) + (devfn << 12); + return base + where + (devfn << 12); }
static int cns3xxx_pci_read_config(struct pci_bus *bus, unsigned int devfn,