x86: EDAC: MCE: Fix MCE decoding callback logic

Make decoding of MCEs happen only on AMD hardware by registering a
non-default callback only on CPU families which support it.

While looking at the interaction of decode_mce() with the other MCE
code i also noticed a few other things and made the following
cleanups/fixes:

 - Fixed the mce_decode() weak alias - a weak alias is really not
   good here, it should be a proper callback. A weak alias will be
   overriden if a piece of code is built into the kernel - not
   good, obviously.

 - The patch initializes the callback on AMD family 10h and 11h.

 - Added the more correct fallback printk of:

	No support for human readable MCE decoding on this CPU type.
	Transcribe the message and run it through 'mcelog --ascii' to decode.

   On CPUs that dont have a decoder.

 - Made the surrounding code more readable.

Note that the callback allows us to have a default fallback -
without having to check the CPU versions during the printout
itself. When an EDAC module registers itself, it can install the
decode-print function.

(there's no unregister needed as this is core code.)

version -v2 by Borislav Petkov:

 - add K8 to the set of supported CPUs

 - always build in edac_mce_amd since we use an early_initcall now

 - fix checkpatch warnings

Signed-off-by: Borislav Petkov <borislav.petkov@amd.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andi Kleen <andi@firstfloor.org>
LKML-Reference: <20091001141432.GA11410@aftab>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

2 files changed, 15 insertions, 2 deletions

diff --git a/drivers/edac/Makefile b/drivers/edac/Makefile
index 7a473bb..8701cd7 100644
--- a/drivers/edac/Makefile
+++ b/drivers/edac/Makefile
@@ -18,7 +18,7 @@ edac_core-objs	+= edac_pci.o edac_pci_sysfs.o
 endif
 
 ifdef CONFIG_CPU_SUP_AMD
-edac_core-objs  += edac_mce_amd.o
+obj-$(CONFIG_X86_MCE)			+= edac_mce_amd.o
 endif
 
 obj-$(CONFIG_EDAC_AMD76X)		+= amd76x_edac.o
diff --git a/drivers/edac/edac_mce_amd.c b/drivers/edac/edac_mce_amd.c
index 0c21c37..83a01a1 100644
--- a/drivers/edac/edac_mce_amd.c
+++ b/drivers/edac/edac_mce_amd.c
@@ -362,7 +362,7 @@ static inline void amd_decode_err_code(unsigned int ec)
 		pr_warning("Huh? Unknown MCE error 0x%x\n", ec);
 }
 
-void decode_mce(struct mce *m)
+static void amd_decode_mce(struct mce *m)
 {
 	struct err_regs regs;
 	int node, ecc;
@@ -420,3 +420,16 @@ void decode_mce(struct mce *m)
 
 	amd_decode_err_code(m->status & 0xffff);
 }
+
+static int __init mce_amd_init(void)
+{
+	/*
+	 * We can decode MCEs for Opteron and later CPUs:
+	 */
+	if ((boot_cpu_data.x86_vendor == X86_VENDOR_AMD) &&
+	    (boot_cpu_data.x86 >= 0xf))
+		x86_mce_decode_callback = amd_decode_mce;
+
+	return 0;
+}
+early_initcall(mce_amd_init);