powerpc/fsl-corenet: work around erratum A004510

Erratum A004510 says that under certain load conditions, modified
cache lines can be discarded, causing data corruption.

To work around this, several CCSR and DCSR register updates need to be
made in a careful manner, so that there is no other transaction in
corenet when the update is made.

The update is made from a locked cacheline, with a delay before to flush
any previous activity, and a delay after to flush the CCSR/DCSR update.
We can't use a readback because that would be another corenet
transaction, which is not allowed.

We lock the subsequent cacheline to prevent it from being fetched while
we're executing the previous cacheline.  It is filled with nops so that a
branch doesn't cause us to fetch another cacheline.

Ordinarily we are running in a cache-inhibited mapping at this point, so
we temporarily change that.  We make it guarded so that we should never
see a speculative load, and we never do an explicit load.  Thus, only the
I-cache should ever fill from this mapping, and we flush/unlock it
afterward.  Thus we should avoid problems from any potential cache
aliasing between inhibited and non-inhibited mappings.

NOTE that if PAMU is used with this patch, it will need to use a
dedicated LAW as described in the erratum.  This is the responsibility
of the OS that sets up PAMU.

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

1 files changed, 2 insertions, 0 deletions

diff --git a/arch/powerpc/include/asm/processor.h b/arch/powerpc/include/asm/processor.h
index c942bec195..a8ffedbc86 100644
--- a/arch/powerpc/include/asm/processor.h
+++ b/arch/powerpc/include/asm/processor.h
@@ -486,11 +486,13 @@
 #define SPRN_L2CFG0	0x207	/* L2 Cache Configuration Register 0 */
 #define SPRN_L1CSR0	0x3f2	/* L1 Data Cache Control and Status Register 0 */
 #define   L1CSR0_CPE		0x00010000	/* Data Cache Parity Enable */
+#define   L1CSR0_CUL		0x00000400	/* (D-)Cache Unable to Lock */
 #define   L1CSR0_DCLFR		0x00000100	/* D-Cache Lock Flash Reset */
 #define   L1CSR0_DCFI		0x00000002	/* Data Cache Flash Invalidate */
 #define   L1CSR0_DCE		0x00000001	/* Data Cache Enable */
 #define SPRN_L1CSR1	0x3f3	/* L1 Instruction Cache Control and Status Register 1 */
 #define   L1CSR1_CPE		0x00010000	/* Instruction Cache Parity Enable */
+#define   L1CSR1_ICUL		0x00000400	/* I-Cache Unable to Lock */
 #define   L1CSR1_ICLFR		0x00000100	/* I-Cache Lock Flash Reset */
 #define   L1CSR1_ICFI		0x00000002	/* Instruction Cache Flash Invalidate */
 #define   L1CSR1_ICE		0x00000001	/* Instruction Cache Enable */