linux-kernel - [PATCH V4 03/17] arm64/cpufeature: Make doublelock a signed feature in ID

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Message-Id: <1589881254-10082-4-git-send-email-anshuman.khandual@arm.com>
Date:   Tue, 19 May 2020 15:10:40 +0530
From:   Anshuman Khandual <anshuman.khandual@....com>
To:     linux-arm-kernel@...ts.infradead.org
Cc:     catalin.marinas@....com, will@...nel.org, maz@...nel.org,
        mark.rutland@....com, suzuki.poulose@....com,
        Anshuman Khandual <anshuman.khandual@....com>,
        linux-kernel@...r.kernel.org
Subject: [PATCH V4 03/17] arm64/cpufeature: Make doublelock a signed feature in ID_AA64DFR0

Double lock feature can have the following possible values.

0b0000 - Double lock implemented
0b1111 - Double lock not implemented

But in case of a conflict the safe value should be 0b1111. Hence this must
be a signed feature instead. Also change FTR_EXACT to FTR_LOWER_SAFE. While
here, fix the erroneous bit width value from 28 to 4.

Cc: Catalin Marinas <catalin.marinas@....com>
Cc: Will Deacon <will@...nel.org>
Cc: Mark Rutland <mark.rutland@....com>
Cc: Suzuki K Poulose <suzuki.poulose@....com>
Cc: linux-arm-kernel@...ts.infradead.org
Cc: linux-kernel@...r.kernel.org

Suggested-by: Suzuki K Poulose <suzuki.poulose@....com>
Signed-off-by: Anshuman Khandual <anshuman.khandual@....com>
---
 arch/arm64/kernel/cpufeature.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index 425d8ab1eda1..0d2b011c5930 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -343,7 +343,7 @@ static const struct arm64_ftr_bits ftr_id_mmfr0[] = {
 };
 
 static const struct arm64_ftr_bits ftr_id_aa64dfr0[] = {
-	ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_EXACT, 36, 28, 0),
+	S_ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, 36, 4, 0),
 	ARM64_FTR_BITS(FTR_HIDDEN, FTR_NONSTRICT, FTR_LOWER_SAFE, ID_AA64DFR0_PMSVER_SHIFT, 4, 0),
 	ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, ID_AA64DFR0_CTX_CMPS_SHIFT, 4, 0),
 	ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, ID_AA64DFR0_WRPS_SHIFT, 4, 0),
-- 
2.20.1