arm64: Add work around for Arm Cortex-A55 Erratum 1024718

BugLink: https://bugs.launchpad.net/bugs/1775477

commit ece1397c upstream.

Some variants of the Arm Cortex-55 cores (r0p0, r0p1, r1p0) suffer
from an erratum 1024718, which causes incorrect updates when DBM/AP
bits in a page table entry is modified without a break-before-make
sequence. The work around is to skip enabling the hardware DBM feature
on the affected cores. The hardware Access Flag management features
is not affected. There are some other cores suffering from this
errata, which could be added to the midr_list to trigger the work
around.

Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: ckadabi@codeaurora.org
Reviewed-by: Dave Martin <dave.martin@arm.com>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>
Acked-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>

arch/arm64/Kconfig

@@ -379,6 +379,20 @@ config ARM64_ERRATUM_843419
 
 	  If unsure, say Y.
 
+config ARM64_ERRATUM_1024718
+	bool "Cortex-A55: 1024718: Update of DBM/AP bits without break before make might result in incorrect update"
+	default y
+	help
+	  This option adds work around for Arm Cortex-A55 Erratum 1024718.
+
+	  Affected Cortex-A55 cores (r0p0, r0p1, r1p0) could cause incorrect
+	  update of the hardware dirty bit when the DBM/AP bits are updated
+	  without a break-before-make. The work around is to disable the usage
+	  of hardware DBM locally on the affected cores. CPUs not affected by
+	  erratum will continue to use the feature.
+
+	  If unsure, say Y.
+
 config CAVIUM_ERRATUM_22375
 	bool "Cavium erratum 22375, 24313"
 	default y

arch/arm64/include/asm/assembler.h

@@ -23,6 +23,7 @@
 #ifndef __ASM_ASSEMBLER_H
 #define __ASM_ASSEMBLER_H
 
+#include <asm/cputype.h>
 #include <asm/ptrace.h>
 #include <asm/thread_info.h>
 
@@ -224,4 +225,43 @@ lr	.req	x30		// link register
 	movk	\reg, :abs_g0_nc:\val
 	.endm
 
+/*
+ * Check the MIDR_EL1 of the current CPU for a given model and a range of
+ * variant/revision. See asm/cputype.h for the macros used below.
+ *
+ *	model:		MIDR_CPU_PART of CPU
+ *	rv_min:		Minimum of MIDR_CPU_VAR_REV()
+ *	rv_max:		Maximum of MIDR_CPU_VAR_REV()
+ *	res:		Result register.
+ *	tmp1, tmp2, tmp3: Temporary registers
+ *
+ * Corrupts: res, tmp1, tmp2, tmp3
+ * Returns:  0, if the CPU id doesn't match. Non-zero otherwise
+ */
+	.macro	cpu_midr_match model, rv_min, rv_max, res, tmp1, tmp2, tmp3
+	mrs		\res, midr_el1
+	mov_q		\tmp1, (MIDR_REVISION_MASK | MIDR_VARIANT_MASK)
+	mov_q		\tmp2, MIDR_CPU_MODEL_MASK
+	and		\tmp3, \res, \tmp2	// Extract model
+	and		\tmp1, \res, \tmp1	// rev & variant
+	mov_q		\tmp2, \model
+	cmp		\tmp3, \tmp2
+	cset		\res, eq
+	cbz		\res, .Ldone\@		// Model matches ?
+
+	.if (\rv_min != 0)			// Skip min check if rv_min == 0
+	mov_q		\tmp3, \rv_min
+	cmp		\tmp1, \tmp3
+	cset		\res, ge
+	.endif					// \rv_min != 0
+	/* Skip rv_max check if rv_min == rv_max && rv_min != 0 */
+	.if ((\rv_min != \rv_max) || \rv_min == 0)
+	mov_q		\tmp2, \rv_max
+	cmp		\tmp1, \tmp2
+	cset		\tmp2, le
+	and		\res, \res, \tmp2
+	.endif
+.Ldone\@:
+	.endm
+
 #endif	/* __ASM_ASSEMBLER_H */

arch/arm64/include/asm/cputype.h

@@ -57,6 +57,9 @@
 #define MIDR_IMPLEMENTOR(midr)	\
 	(((midr) & MIDR_IMPLEMENTOR_MASK) >> MIDR_IMPLEMENTOR_SHIFT)
 
+#define MIDR_CPU_VAR_REV(var, rev) \
+	(((var) << MIDR_VARIANT_SHIFT) | (rev))
+
 #define MIDR_CPU_MODEL(imp, partnum) \
 	(((imp)			<< MIDR_IMPLEMENTOR_SHIFT) | \
 	(0xf			<< MIDR_ARCHITECTURE_SHIFT) | \
@@ -81,13 +84,16 @@
 #define ARM_CPU_PART_FOUNDATION		0xD00
 #define ARM_CPU_PART_CORTEX_A57		0xD07
 #define ARM_CPU_PART_CORTEX_A53		0xD03
+#define ARM_CPU_PART_CORTEX_A55		0xD05
 
 #define APM_CPU_PART_POTENZA		0x000
 
 #define CAVIUM_CPU_PART_THUNDERX	0x0A1
 
+
 #define MIDR_CORTEX_A53 MIDR_CPU_MODEL(ARM_CPU_IMP_ARM, ARM_CPU_PART_CORTEX_A53)
 #define MIDR_CORTEX_A57 MIDR_CPU_MODEL(ARM_CPU_IMP_ARM, ARM_CPU_PART_CORTEX_A57)
+#define MIDR_CORTEX_A55 MIDR_CPU_MODEL(ARM_CPU_IMP_ARM, ARM_CPU_PART_CORTEX_A55)
 #define MIDR_THUNDERX	MIDR_CPU_MODEL(ARM_CPU_IMP_CAVIUM, CAVIUM_CPU_PART_THUNDERX)
 
 #ifndef __ASSEMBLY__

arch/arm64/mm/proc.S

@@ -221,6 +221,11 @@ ENTRY(__cpu_setup)
 	cbz	x9, 2f
 	cmp	x9, #2
 	b.lt	1f
+#ifdef CONFIG_ARM64_ERRATUM_1024718
+	/* Disable hardware DBM on Cortex-A55 r0p0, r0p1 & r1p0 */
+	cpu_midr_match MIDR_CORTEX_A55, MIDR_CPU_VAR_REV(0, 0), MIDR_CPU_VAR_REV(1, 0), x1, x2, x3, x4
+	cbnz	x1, 1f
+#endif
 	orr	x10, x10, #TCR_HD		// hardware Dirty flag update
 1:	orr	x10, x10, #TCR_HA		// hardware Access flag update
 2: