[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>

1 files changed, 14 insertions, 6 deletions

diff --git a/include/asm-arm/arch-ixp2000/io.h b/include/asm-arm/arch-ixp2000/io.h
index 5e56b47446e0..3241cd6f0778 100644
--- a/include/asm-arm/arch-ixp2000/io.h
+++ b/include/asm-arm/arch-ixp2000/io.h
@@ -17,16 +17,21 @@
 
 #define IO_SPACE_LIMIT          0xffffffff
 #define __mem_pci(a)            (a)
-#define ___io(p)                ((void __iomem *)((p)+IXP2000_PCI_IO_VIRT_BASE))
 
 /*
- * The IXP2400 before revision B0 asserts byte lanes for PCI I/O
+ * The A? revisions of the IXP2000s assert byte lanes for PCI I/O
  * transactions the other way round (MEM transactions don't have this
- * issue), so we need to override the standard functions.  B0 and later
- * have a bit that can be set to 1 to get the 'proper' behavior, but
- * since that isn't available on the A? revisions we just keep doing
- * things manually.
+ * issue), so if we want to support those models, we need to override
+ * the standard I/O functions.
+ *
+ * B0 and later have a bit that can be set to 1 to get the proper
+ * behavior for I/O transactions, which then allows us to use the
+ * standard I/O functions.  This is what we do if the user does not
+ * explicitly ask for support for pre-B0.
  */
+#ifdef CONFIG_IXP2000_SUPPORT_BROKEN_PCI_IO
+#define ___io(p)                ((void __iomem *)((p)+IXP2000_PCI_IO_VIRT_BASE))
+
 #define alignb(addr)            (void __iomem *)((unsigned long)(addr) ^ 3)
 #define alignw(addr)            (void __iomem *)((unsigned long)(addr) ^ 2)
 
@@ -119,6 +124,9 @@
 #define ioport_map(port, nr)    ___io(port)
 
 #define ioport_unmap(addr)
+#else
+#define __io(p)                 ((void __iomem *)((p)+IXP2000_PCI_IO_VIRT_BASE))
+#endif
 
 
 #ifdef CONFIG_ARCH_IXDP2X01