[PATCH 4/6] arm64: add Cortex-A53 cache errata workaround

[Andre Przywara]

The ARM errata 819472, 826319, 827319 and 824069 define the same
workaround for these hardware issues in certain Cortex-A53 parts.
Use the new alternatives framework and the CPU MIDR detection to
patch "cache clean" into "cache clean and invalidate" instructions if
an affected CPU is detected at runtime.

Signed-off-by: Andre Przywara <andre.przywara at arm.com>
---
 arch/arm64/include/asm/alternative-asm.h |   13 ++++++++++++
 arch/arm64/include/asm/cpufeature.h      |    8 +++++++-
 arch/arm64/include/asm/cputype.h         |    5 +++++
 arch/arm64/kernel/cpu_errata.c           |   32 +++++++++++++++++++++++++++++-
 arch/arm64/mm/cache.S                    |    4 +++-
 5 files changed, 59 insertions(+), 3 deletions(-)

diff --git a/arch/arm64/include/asm/alternative-asm.h b/arch/arm64/include/asm/alternative-asm.h
index 5ee9340..919a678 100644
--- a/arch/arm64/include/asm/alternative-asm.h
+++ b/arch/arm64/include/asm/alternative-asm.h
@@ -11,6 +11,19 @@
 	.byte \alt_len
 .endm
 
+.macro alternative_insn insn1 insn2 cap
+661:	\insn1
+662:	.pushsection .altinstructions, "a"
+	altinstruction_entry 661b, 663f, \cap, 662b-661b, 664f-663f
+	.popsection
+	.pushsection .altinstr_replacement, "ax"
+663:	\insn2
+664:	.popsection
+	.if ((664b-663b) != (662b-661b))
+		.error "Alternatives instruction length mismatch"
+	.endif
+.endm
+
 #endif  /*  __ASSEMBLY__  */
 
 #endif /* __ASM_ALTERNATIVE_ASM_H */
diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h
index 744eaf7..92b6ee4 100644
--- a/arch/arm64/include/asm/cpufeature.h
+++ b/arch/arm64/include/asm/cpufeature.h
@@ -21,7 +21,11 @@
 #define MAX_CPU_FEATURES	(8 * sizeof(elf_hwcap))
 #define cpu_feature(x)		ilog2(HWCAP_ ## x)
 
-#define NCAPS			0
+#define ARM64_WORKAROUND_CLEAN_CACHE	0
+
+#define NCAPS				1
+
+#ifndef __ASSEMBLY__
 
 extern DECLARE_BITMAP(cpu_hwcaps, NCAPS);
 
@@ -48,4 +52,6 @@ static inline void cpus_set_cap(unsigned int num)
 
 void check_local_cpu_errata(void);
 
+#endif /* __ASSEMBLY__ */
+
 #endif
diff --git a/arch/arm64/include/asm/cputype.h b/arch/arm64/include/asm/cputype.h
index 379d0b8..8adb986 100644
--- a/arch/arm64/include/asm/cputype.h
+++ b/arch/arm64/include/asm/cputype.h
@@ -57,6 +57,11 @@
 #define MIDR_IMPLEMENTOR(midr)	\
 	(((midr) & MIDR_IMPLEMENTOR_MASK) >> MIDR_IMPLEMENTOR_SHIFT)
 
+#define MIDR_CPU_PART(imp, partnum) \
+	(((imp)			<< MIDR_IMPLEMENTOR_SHIFT) | \
+	(0xf			<< MIDR_ARCHITECTURE_SHIFT) | \
+	((partnum)		<< MIDR_PARTNUM_SHIFT))
+
 #define ARM_CPU_IMP_ARM		0x41
 #define ARM_CPU_IMP_APM		0x50
 
diff --git a/arch/arm64/kernel/cpu_errata.c b/arch/arm64/kernel/cpu_errata.c
index 9332cf7..875fb2c 100644
--- a/arch/arm64/kernel/cpu_errata.c
+++ b/arch/arm64/kernel/cpu_errata.c
@@ -23,6 +23,8 @@
 #include <asm/cputype.h>
 #include <asm/cpufeature.h>
 
+#define MIDR_CORTEX_A53 MIDR_CPU_PART(ARM_CPU_IMP_ARM, ARM_CPU_PART_CORTEX_A53)
+
 /*
  * Add a struct or another datatype to the union below if you need
  * different means to detect an affected CPU.
@@ -39,8 +41,36 @@ struct arm64_cpu_capabilities {
 	};
 };
 
+#define CPU_MODEL_MASK (MIDR_IMPLEMENTOR_MASK | MIDR_PARTNUM_MASK | \
+			MIDR_ARCHITECTURE_MASK)
+
+static bool is_affected_midr_range(struct arm64_cpu_capabilities *entry)
+{
+	u32 midr = read_cpuid_id();
+
+	if ((midr & CPU_MODEL_MASK) != entry->midr_model)
+		return false;
+
+	midr &= MIDR_REVISION_MASK | MIDR_VARIANT_MASK;
+
+	return (midr >= entry->midr_range_min && midr <= entry->midr_range_max);
+}
+
+#define MIDR_RANGE(model, min, max) \
+	.is_affected = is_affected_midr_range, \
+	.midr_model = model, \
+	.midr_range_min = min, \
+	.midr_range_max = max
+
 struct arm64_cpu_capabilities arm64_errata[] = {
-	{}
+	{
+	/* Cortex-A53 r0p[012] */
+		.desc = "ARM errata 826319, 827319, 824069",
+		.capability = ARM64_WORKAROUND_CLEAN_CACHE,
+		MIDR_RANGE(MIDR_CORTEX_A53, 0x00, 0x02),
+	},
+	{
+	}
 };
 
 void check_local_cpu_errata(void)
diff --git a/arch/arm64/mm/cache.S b/arch/arm64/mm/cache.S
index 2366383..8eaf185 100644
--- a/arch/arm64/mm/cache.S
+++ b/arch/arm64/mm/cache.S
@@ -20,6 +20,8 @@
 #include <linux/linkage.h>
 #include <linux/init.h>
 #include <asm/assembler.h>
+#include <asm/cpufeature.h>
+#include <asm/alternative-asm.h>
 
 #include "proc-macros.S"
 
@@ -210,7 +212,7 @@ __dma_clean_range:
 	dcache_line_size x2, x3
 	sub	x3, x2, #1
 	bic	x0, x0, x3
-1:	dc	cvac, x0			// clean D / U line
+1:	alternative_insn "dc cvac, x0", "dc civac, x0", ARM64_WORKAROUND_CLEAN_CACHE
 	add	x0, x0, x2
 	cmp	x0, x1
 	b.lo	1b
-- 
1.7.9.5