[PATCH 7/7] arm64: arch_timer: Add workaround for ARM erratum 1188873

[marc.zyngier@arm.com (Marc Zyngier)]

When running on Cortex-A76, a timer access from an AArch32 EL0
task may end up with a corrupted value or register. The workaround for
this is to trap these accesses at EL1/EL2 and execute them there.

This only affects versions r0p0, r1p0 and r2p0 of the CPU.

Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
---
 arch/arm64/Kconfig                   | 12 ++++++++++++
 arch/arm64/include/asm/cpucaps.h     |  3 ++-
 arch/arm64/include/asm/cputype.h     |  2 ++
 arch/arm64/kernel/cpu_errata.c       |  8 ++++++++
 drivers/clocksource/arm_arch_timer.c | 15 +++++++++++++++
 5 files changed, 39 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 1b1a0e95c751..28766066f31b 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -479,6 +479,18 @@ config ARM64_ERRATUM_1024718
 
 	  If unsure, say Y.
 
+config ARM64_ERRATUM_1188873
+	bool "Cortex-A76: MRC read following MRRC read of specific Generic Timer in AArch32 might give incorrect result"
+	default y
+	help
+	  This option adds work arounds for ARM Cortex-A76 erratum 1188873
+
+	  Affected Cortex-A76 cores (r0p0, r1p0, r2p0) could cause
+	  register corruption when accessing the timer registers from
+	  AArch32 userspace.
+
+	  If unsure, say Y.
+
 config CAVIUM_ERRATUM_22375
 	bool "Cavium erratum 22375, 24313"
 	default y
diff --git a/arch/arm64/include/asm/cpucaps.h b/arch/arm64/include/asm/cpucaps.h
index ae1f70450fb2..3575331dea7b 100644
--- a/arch/arm64/include/asm/cpucaps.h
+++ b/arch/arm64/include/asm/cpucaps.h
@@ -51,7 +51,8 @@
 #define ARM64_SSBD				30
 #define ARM64_MISMATCHED_CACHE_TYPE		31
 #define ARM64_HAS_STAGE2_FWB			32
+#define ARM64_WORKAROUND_1188873		33
 
-#define ARM64_NCAPS				33
+#define ARM64_NCAPS				34
 
 #endif /* __ASM_CPUCAPS_H */
diff --git a/arch/arm64/include/asm/cputype.h b/arch/arm64/include/asm/cputype.h
index ea690b3562af..12f93e4d2452 100644
--- a/arch/arm64/include/asm/cputype.h
+++ b/arch/arm64/include/asm/cputype.h
@@ -86,6 +86,7 @@
 #define ARM_CPU_PART_CORTEX_A75		0xD0A
 #define ARM_CPU_PART_CORTEX_A35		0xD04
 #define ARM_CPU_PART_CORTEX_A55		0xD05
+#define ARM_CPU_PART_CORTEX_A76		0xD0B
 
 #define APM_CPU_PART_POTENZA		0x000
 
@@ -110,6 +111,7 @@
 #define MIDR_CORTEX_A75 MIDR_CPU_MODEL(ARM_CPU_IMP_ARM, ARM_CPU_PART_CORTEX_A75)
 #define MIDR_CORTEX_A35 MIDR_CPU_MODEL(ARM_CPU_IMP_ARM, ARM_CPU_PART_CORTEX_A35)
 #define MIDR_CORTEX_A55 MIDR_CPU_MODEL(ARM_CPU_IMP_ARM, ARM_CPU_PART_CORTEX_A55)
+#define MIDR_CORTEX_A76	MIDR_CPU_MODEL(ARM_CPU_IMP_ARM, ARM_CPU_PART_CORTEX_A76)
 #define MIDR_THUNDERX	MIDR_CPU_MODEL(ARM_CPU_IMP_CAVIUM, CAVIUM_CPU_PART_THUNDERX)
 #define MIDR_THUNDERX_81XX MIDR_CPU_MODEL(ARM_CPU_IMP_CAVIUM, CAVIUM_CPU_PART_THUNDERX_81XX)
 #define MIDR_THUNDERX_83XX MIDR_CPU_MODEL(ARM_CPU_IMP_CAVIUM, CAVIUM_CPU_PART_THUNDERX_83XX)
diff --git a/arch/arm64/kernel/cpu_errata.c b/arch/arm64/kernel/cpu_errata.c
index dec10898d688..16c102d96e6d 100644
--- a/arch/arm64/kernel/cpu_errata.c
+++ b/arch/arm64/kernel/cpu_errata.c
@@ -679,6 +679,14 @@ const struct arm64_cpu_capabilities arm64_errata[] = {
 		.type = ARM64_CPUCAP_LOCAL_CPU_ERRATUM,
 		.matches = has_ssbd_mitigation,
 	},
+#endif
+#ifdef CONFIG_ARM64_ERRATUM_1188873
+	{
+		/* Cortex-A76 r0p0 to r2p0 */
+		.desc = "ARM erratum 1188873",
+		.capability = ARM64_WORKAROUND_1188873,
+		ERRATA_MIDR_RANGE(MIDR_CORTEX_A76, 0, 0, 2, 0),
+	},
 #endif
 	{
 	}
diff --git a/drivers/clocksource/arm_arch_timer.c b/drivers/clocksource/arm_arch_timer.c
index d8c7f5750cdb..9a7d4dc00b6e 100644
--- a/drivers/clocksource/arm_arch_timer.c
+++ b/drivers/clocksource/arm_arch_timer.c
@@ -319,6 +319,13 @@ static u64 notrace arm64_858921_read_cntvct_el0(void)
 }
 #endif
 
+#ifdef CONFIG_ARM64_ERRATUM_1188873
+static u64 notrace arm64_1188873_read_cntvct_el0(void)
+{
+	return read_sysreg(cntvct_el0);
+}
+#endif
+
 #ifdef CONFIG_ARM_ARCH_TIMER_OOL_WORKAROUND
 DEFINE_PER_CPU(const struct arch_timer_erratum_workaround *, timer_unstable_counter_workaround);
 EXPORT_SYMBOL_GPL(timer_unstable_counter_workaround);
@@ -408,6 +415,14 @@ static const struct arch_timer_erratum_workaround ool_workarounds[] = {
 		.read_cntvct_el0 = arm64_858921_read_cntvct_el0,
 	},
 #endif
+#ifdef CONFIG_ARM64_ERRATUM_1188873
+	{
+		.match_type = ate_match_local_cap_id,
+		.id = (void *)ARM64_WORKAROUND_1188873,
+		.desc = "ARM erratum 1188873",
+		.read_cntvct_el0 = arm64_1188873_read_cntvct_el0,
+	},
+#endif
 };
 
 typedef bool (*ate_match_fn_t)(const struct arch_timer_erratum_workaround *,
-- 
2.19.0