powerpc/fsl-booke: Work around erratum A-006958

Erratum A-006598 says that 64-bit mftb is not atomic -- it's subject
to a similar race condition as doing mftbu/mftbl on 32-bit.  The lower
half of timebase is updated before the upper half; thus, we can share
the workaround for a similar bug on Cell.  This workaround involves
looping if the lower half of timebase is zero, thus avoiding the need
for a scratch register (other than CR0).  This workaround must be
avoided when the timebase is frozen, such as during the timebase sync
code.

This deals with kernel and vdso accesses, but other userspace accesses
will of course need to be fixed elsewhere.

Signed-off-by: Scott Wood <scottwood@freescale.com>

1 files changed, 7 insertions, 2 deletions

diff --git a/arch/powerpc/include/asm/cputable.h b/arch/powerpc/include/asm/cputable.h
index 6f3887d884d2..0d4939ba48e7 100644
--- a/arch/powerpc/include/asm/cputable.h
+++ b/arch/powerpc/include/asm/cputable.h
@@ -371,14 +371,19 @@ extern const char *powerpc_base_platform;
 #define CPU_FTRS_E500MC (CPU_FTR_USE_TB | CPU_FTR_NODSISRALIGN | \
             CPU_FTR_L2CSR | CPU_FTR_LWSYNC | CPU_FTR_NOEXECUTE | \
             CPU_FTR_DBELL | CPU_FTR_DEBUG_LVL_EXC | CPU_FTR_EMB_HV)
+/*
+ * e5500/e6500 erratum A-006958 is a timebase bug that can use the
+ * same workaround as CPU_FTR_CELL_TB_BUG.
+ */
 #define CPU_FTRS_E5500  (CPU_FTR_USE_TB | CPU_FTR_NODSISRALIGN | \
             CPU_FTR_L2CSR | CPU_FTR_LWSYNC | CPU_FTR_NOEXECUTE | \
             CPU_FTR_DBELL | CPU_FTR_POPCNTB | CPU_FTR_POPCNTD | \
-            CPU_FTR_DEBUG_LVL_EXC | CPU_FTR_EMB_HV)
+            CPU_FTR_DEBUG_LVL_EXC | CPU_FTR_EMB_HV | CPU_FTR_CELL_TB_BUG)
 #define CPU_FTRS_E6500  (CPU_FTR_USE_TB | CPU_FTR_NODSISRALIGN | \
             CPU_FTR_L2CSR | CPU_FTR_LWSYNC | CPU_FTR_NOEXECUTE | \
             CPU_FTR_DBELL | CPU_FTR_POPCNTB | CPU_FTR_POPCNTD | \
-            CPU_FTR_DEBUG_LVL_EXC | CPU_FTR_EMB_HV | CPU_FTR_ALTIVEC_COMP)
+            CPU_FTR_DEBUG_LVL_EXC | CPU_FTR_EMB_HV | CPU_FTR_ALTIVEC_COMP | \
+            CPU_FTR_CELL_TB_BUG)
 #define CPU_FTRS_GENERIC_32     (CPU_FTR_COMMON | CPU_FTR_NODSISRALIGN)
 
 /* 64-bit CPUs */