[PATCH 1/2] ARM: errata 814220-B-Cache maintenance by set/way operations can execute out of order.

[Benjamin Gaignard]

Description:
The v7 ARM states that all cache and branch predictor maintenance operations
that do not specify an address execute, relative to each other, in program
order. However, because of this erratum, an L2 set/way cache maintenance
operation can overtake an L1 set/way cache maintenance operation, this would
cause the data corruption.

This ERRATA affected the Cortex-A7 and present in r0p2, r0p3, r0p4, r0p5.

This patch is the SW workaround by adding a DSB before changing cache levels as
the ARM ERRATA: ARM/MP: 814220 told in the ARM ERRATA documentation.

Signed-off-by: Jason Liu <r64343@xxxxxxxxxxxxx>
Signed-off-by: Benjamin Gaignard <benjamin.gaignard@xxxxxxxxxx>
---
 arch/arm/Kconfig       | 10 ++++++++++
 arch/arm/mm/cache-v7.S |  3 +++
 2 files changed, 13 insertions(+)

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 664e918e2624..6f608558e22a 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -1227,6 +1227,16 @@ config PCI_HOST_ITE8152
 	default y
 	select DMABOUNCE
 
+config ARM_ERRATA_814220
+	bool "ARM errata: Cache maintenance by set/way operations can execute out of order"
+	depends on CPU_V7
+	help
+	  The v7 ARM states that all cache and branch predictor maintenance operations
+	  that do not specify an address execute, relative to each other, in program order.
+	  However, because of this erratum, an L2 set/way cache maintenance operation can
+	  overtake an L1 set/way cache maintenance operation. This ERRATA only affected the
+	  Cortex-A7 and present in r0p2, r0p3, r0p4, r0p5.
+
 endmenu
 
 menu "Kernel Features"
diff --git a/arch/arm/mm/cache-v7.S b/arch/arm/mm/cache-v7.S
index 2149b47a0c5a..7ff7b4c197cc 100644
--- a/arch/arm/mm/cache-v7.S
+++ b/arch/arm/mm/cache-v7.S
@@ -163,6 +163,9 @@ loop2:
 skip:
 	add	r10, r10, #2			@ increment cache number
 	cmp	r3, r10
+#ifdef CONFIG_ARM_ERRATA_814220
+	dsb
+#endif
 	bgt	flush_levels
 finished:
 	mov	r10, #0				@ switch back to cache level 0
-- 
2.15.0