powerpc: Fixup lwsync at runtime

To allow for a single kernel image on e500 v1/v2/mc we need to fixup lwsync
at runtime.  On e500v1/v2 lwsync causes an illop so we need to patch up
the code.  We default to 'sync' since that is always safe and if the cpu
is capable we will replace 'sync' with 'lwsync'.

We introduce CPU_FTR_LWSYNC as a way to determine at runtime if this is
needed.  This flag could be moved elsewhere since we dont really use it
for the normal CPU_FTR purpose.

Finally we only store the relative offset in the fixup section to keep it
as small as possible rather than using a full fixup_entry.

Signed-off-by: Kumar Gala <galak@kernel.crashing.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>

1 files changed, 36 insertions, 0 deletions

diff --git a/arch/powerpc/lib/feature-fixups.c b/arch/powerpc/lib/feature-fixups.c
index 48e1ed89052d..4e43702b9813 100644
--- a/arch/powerpc/lib/feature-fixups.c
+++ b/arch/powerpc/lib/feature-fixups.c
@@ -110,6 +110,22 @@ void do_feature_fixups(unsigned long value, void *fixup_start, void *fixup_end)
         }
 }
 
+void do_lwsync_fixups(unsigned long value, void *fixup_start, void *fixup_end)
+{
+        unsigned int *start, *end, *dest;
+
+        if (!(value & CPU_FTR_LWSYNC))
+                return ;
+
+        start = fixup_start;
+        end = fixup_end;
+
+        for (; start < end; start++) {
+                dest = (void *)start + *start;
+                patch_instruction(dest, PPC_LWSYNC_INSTR);
+        }
+}
+
 #ifdef CONFIG_FTR_FIXUP_SELFTEST
 
 #define check(x)        \
@@ -295,6 +311,25 @@ static void test_fw_macros(void)
 #endif
 }
 
+static void test_lwsync_macros(void)
+{
+        extern void lwsync_fixup_test;
+        extern void end_lwsync_fixup_test;
+        extern void lwsync_fixup_test_expected_LWSYNC;
+        extern void lwsync_fixup_test_expected_SYNC;
+        unsigned long size = &end_lwsync_fixup_test -
+                             &lwsync_fixup_test;
+
+        /* The fixups have already been done for us during boot */
+        if (cur_cpu_spec->cpu_features & CPU_FTR_LWSYNC) {
+                check(memcmp(&lwsync_fixup_test,
+                             &lwsync_fixup_test_expected_LWSYNC, size) == 0);
+        } else {
+                check(memcmp(&lwsync_fixup_test,
+                             &lwsync_fixup_test_expected_SYNC, size) == 0);
+        }
+}
+
 static int __init test_feature_fixups(void)
 {
         printk(KERN_DEBUG "Running feature fixup self-tests ...\n");
@@ -307,6 +342,7 @@ static int __init test_feature_fixups(void)
         test_alternative_case_with_external_branch();
         test_cpu_macros();
         test_fw_macros();
+        test_lwsync_macros();
 
         return 0;
 }