linux-kernel - [PATCH 2/3] arm64: Add assembly helpers for MIDR range check

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Date:   Tue, 16 Jan 2018 10:23:22 +0000
From:   Suzuki K Poulose <suzuki.poulose@....com>
To:     linux-arm-kernel@...ts.infradead.org
Cc:     linux-kernel@...r.kernel.org, catalin.marinas@....com,
        mark.rutland@....com, will.deacon@....com, marc.zyngier@....com,
        Suzuki K Poulose <suzuki.poulose@....com>
Subject: [PATCH 2/3] arm64: Add assembly helpers for MIDR range check

Add a helper to check the MIDR of the running CPU against a given
MODEL and a range of revision and variants (just like we do in
is_affected_midr_range()). This will be useful for early checks
for MIDR to detect CPU errata.

Cc: Mark Rutland <mark.rutland@....com>
Cc: Catalin Marinas <catalin.marinas@....com>
Cc: Will Deacon <will.deacon@....com>
Cc: Marc Zyngier <marc.zyngier@....com>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@....com>
---
 arch/arm64/include/asm/assembler.h | 40 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 40 insertions(+)

diff --git a/arch/arm64/include/asm/assembler.h b/arch/arm64/include/asm/assembler.h
index 5dc4856f3bb9..596b693edb2c 100644
--- a/arch/arm64/include/asm/assembler.h
+++ b/arch/arm64/include/asm/assembler.h
@@ -25,6 +25,7 @@
 
 #include <asm/asm-offsets.h>
 #include <asm/cpufeature.h>
+#include <asm/cputype.h>
 #include <asm/debug-monitors.h>
 #include <asm/page.h>
 #include <asm/pgtable-hwdef.h>
@@ -516,4 +517,43 @@ alternative_endif
 #endif
 	.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_MODEL 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 */
-- 
2.13.6