OMAP3: PM: Clear the SCTLR C bit in asm code to prevent data cache allocation

On the newer ARM processors like CortexA8, CortexA9, the caches can be
speculatively loaded while they are getting flushed.

Clear the SCTLR C bit to prevent further data cache allocation as
part of cache clean routine

Signed-off-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
Signed-off-by: Kevin Hilman <khilman@ti.com>

1 files changed, 27 insertions, 0 deletions

diff --git a/arch/arm/mach-omap2/sleep34xx.S b/arch/arm/mach-omap2/sleep34xx.S
index 99e43cc5a503..e60ac1f71bd4 100644
--- a/arch/arm/mach-omap2/sleep34xx.S
+++ b/arch/arm/mach-omap2/sleep34xx.S
@@ -246,6 +246,27 @@ clean_caches:
          *  - it executes in a cached space so is faster than refetch per-block
          *  - should be faster and will change with kernel
          *  - 'might' have to copy address, load and jump to it
+         * Flush all data from the L1 data cache before disabling
+         * SCTLR.C bit.
+         */
+        ldr     r1, kernel_flush
+        mov     lr, pc
+        bx      r1
+
+        /*
+         * Clear the SCTLR.C bit to prevent further data cache
+         * allocation. Clearing SCTLR.C would make all the data accesses
+         * strongly ordered and would not hit the cache.
+         */
+        mrc     p15, 0, r0, c1, c0, 0
+        bic     r0, r0, #(1 << 2)       @ Disable the C bit
+        mcr     p15, 0, r0, c1, c0, 0
+        isb
+
+        /*
+         * Invalidate L1 data cache. Even though only invalidate is
+         * necessary exported flush API is used here. Doing clean
+         * on already clean cache would be almost NOP.
          */
         ldr     r1, kernel_flush
         blx     r1
@@ -295,6 +316,12 @@ omap3_do_wfi:
         nop
         bl wait_sdrc_ok
 
+        mrc     p15, 0, r0, c1, c0, 0
+        tst     r0, #(1 << 2)           @ Check C bit enabled?
+        orreq   r0, r0, #(1 << 2)       @ Enable the C bit if cleared
+        mcreq   p15, 0, r0, c1, c0, 0
+        isb
+
 /*
  * ===================================
  * == Exit point from non-OFF modes ==