ARM: 7015/1: ARM errata: Possible cache data corruption with hit-under-miss enabled

This patch is a workaround for the 364296 ARM1136 r0p2 erratum (possible
cache data corruption with hit-under-miss enabled). It sets the
undocumented bit 31 in the auxiliary control register and the FI bit in
the control register, thus disabling hit-under-miss without putting the
processor into full low interrupt latency mode.

Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Tested-by: Siarhei Siamashka <siarhei.siamashka@gmail.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

2 files changed, 28 insertions, 0 deletions

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 5ebc5d922ea..3269576dbfa 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -1271,6 +1271,18 @@ config ARM_ERRATA_754327
           This workaround defines cpu_relax() as smp_mb(), preventing correctly
           written polling loops from denying visibility of updates to memory.
 
+config ARM_ERRATA_364296
+        bool "ARM errata: Possible cache data corruption with hit-under-miss enabled"
+        depends on CPU_V6 && !SMP
+        help
+          This options enables the workaround for the 364296 ARM1136
+          r0p2 erratum (possible cache data corruption with
+          hit-under-miss enabled). It sets the undocumented bit 31 in
+          the auxiliary control register and the FI bit in the control
+          register, thus disabling hit-under-miss without putting the
+          processor into full low interrupt latency mode. ARM11MPCore
+          is not affected.
+
 endmenu
 
 source "arch/arm/common/Kconfig"
diff --git a/arch/arm/mm/proc-v6.S b/arch/arm/mm/proc-v6.S
index 219138d2f15..a923aa0fd00 100644
--- a/arch/arm/mm/proc-v6.S
+++ b/arch/arm/mm/proc-v6.S
@@ -223,6 +223,22 @@ __v6_setup:
         mrc     p15, 0, r0, c1, c0, 0           @ read control register
         bic     r0, r0, r5                      @ clear bits them
         orr     r0, r0, r6                      @ set them
+#ifdef CONFIG_ARM_ERRATA_364296
+        /*
+         * Workaround for the 364296 ARM1136 r0p2 erratum (possible cache data
+         * corruption with hit-under-miss enabled). The conditional code below
+         * (setting the undocumented bit 31 in the auxiliary control register
+         * and the FI bit in the control register) disables hit-under-miss
+         * without putting the processor into full low interrupt latency mode.
+         */
+        ldr     r6, =0x4107b362                 @ id for ARM1136 r0p2
+        mrc     p15, 0, r5, c0, c0, 0           @ get processor id
+        teq     r5, r6                          @ check for the faulty core
+        mrceq   p15, 0, r5, c1, c0, 1           @ load aux control reg
+        orreq   r5, r5, #(1 << 31)              @ set the undocumented bit 31
+        mcreq   p15, 0, r5, c1, c0, 1           @ write aux control reg
+        orreq   r0, r0, #(1 << 21)              @ low interrupt latency configuration
+#endif
         mov     pc, lr                          @ return to head.S:__ret
 
         /*