[PATCH] ARM: 2752/1: disable ixp2000 PCI I/O software workaround on chips that don't need it

Patch from Lennert Buytenhek

The later ixp2000 models don't need the PCI I/O workaround that we
currently perform.  Add a config option to disable the workaround,
and panic on boot if a kernel without the workaround is booted on a
buggy chip.  As only pre-production ixp2000s need the workaround,
the default is for it not to be configured in.

Signed-off-by: Lennert Buytenhek <buytenh@wantstofly.org>
Signed-off-by: Deepak Saxena
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

2 files changed, 21 insertions, 0 deletions

diff --git a/arch/arm/mach-ixp2000/Kconfig b/arch/arm/mach-ixp2000/Kconfig
index 9361e05f6fa3..ecb58d83478e 100644
--- a/arch/arm/mach-ixp2000/Kconfig
+++ b/arch/arm/mach-ixp2000/Kconfig
@@ -54,6 +54,14 @@ config ARCH_IXDP2X01
         depends on ARCH_IXDP2401 || ARCH_IXDP2801
         default y       
 
+config IXP2000_SUPPORT_BROKEN_PCI_IO
+        bool "Support broken PCI I/O on older IXP2000s"
+        default y
+        help
+          Say 'N' here if you only intend to run your kernel on an
+          IXP2000 B0 or later model and do not need the PCI I/O
+          byteswap workaround.  Say 'Y' otherwise.
+
 endmenu
 
 endif
diff --git a/arch/arm/mach-ixp2000/pci.c b/arch/arm/mach-ixp2000/pci.c
index 5ff2f2718c58..0788fb2b5c10 100644
--- a/arch/arm/mach-ixp2000/pci.c
+++ b/arch/arm/mach-ixp2000/pci.c
@@ -198,6 +198,19 @@ clear_master_aborts(void)
 void __init
 ixp2000_pci_preinit(void)
 {
+#ifndef CONFIG_IXP2000_SUPPORT_BROKEN_PCI_IO
+        /*
+         * Configure the PCI unit to properly byteswap I/O transactions,
+         * and verify that it worked.
+         */
+        ixp2000_reg_write(IXP2000_PCI_CONTROL,
+                          (*IXP2000_PCI_CONTROL | PCI_CONTROL_IEE));
+
+        if ((*IXP2000_PCI_CONTROL & PCI_CONTROL_IEE) == 0)
+                panic("IXP2000: PCI I/O is broken on this ixp model, and "
+                        "the needed workaround has not been configured in");
+#endif
+
         hook_fault_code(16+6, ixp2000_pci_abort_handler, SIGBUS,
                                 "PCI config cycle to non-existent device");
 }