[U-Boot] [Patch v2] armv8: Enable CPUECTLR.SMPEN for coherency

[Gong Qianyu]

From: Mingkai Hu <mingkai.hu at nxp.com>

For A53, data coherency is enabled only when the CPUECTLR.SMPEN bit is
set. The SMPEN bit should be set before enabling the data cache.
If not enabled, the cache is not coherent with other cores and
data corruption could occur.

For A57/A72, SMPEN bit enables the processor to receive instruction
cache and TLB maintenance operations broadcast from other processors
in the cluster. This bit should be set before enabling the caches and
MMU, or performing any cache and TLB maintenance operations.

Signed-off-by: Mingkai Hu <mingkai.hu at nxp.com>
Signed-off-by: Gong Qianyu <Qianyu.Gong at nxp.com>
Reviewed-by: Masahiro Yamada <yamada.masahiro at socionext.com>
---
v2:
 - Revise commit message, add for A57/A72 part.
 - Add comments above the code.

 arch/arm/cpu/armv8/start.S | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/arch/arm/cpu/armv8/start.S b/arch/arm/cpu/armv8/start.S
index 670e323..dfce469 100644
--- a/arch/arm/cpu/armv8/start.S
+++ b/arch/arm/cpu/armv8/start.S
@@ -81,6 +81,14 @@ reset:
 	msr	cpacr_el1, x0			/* Enable FP/SIMD */
 0:
 
+	/* Enalbe SMPEN bit for coherency.
+	 * This register is not architectural but at the moment
+	 * this bit should be set for A53/A57/A72.
+	 */
+	mrs     x0, S3_1_c15_c2_1               /* cpuactlr_el1 */
+	orr     x0, x0, #0x40
+	msr     S3_1_c15_c2_1, x0
+
 	/* Apply ARM core specific erratas */
 	bl	apply_core_errata
 
-- 
2.1.0.27.g96db324