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authorJoey Gouly <joey.gouly@arm.com>2021-12-10 19:54:32 +0300
committerCatalin Marinas <catalin.marinas@arm.com>2021-12-13 21:53:00 +0300
commit1175011a7d0030d49dc9c10bde36f08f26d0a8ee (patch)
treed4ec5130ec2454c6e8137c1cb2bab1a04f26d01c /Documentation/arm64
parent9e45365f1469ef2b934f9d035975dbc9ad352116 (diff)
downloadlinux-1175011a7d0030d49dc9c10bde36f08f26d0a8ee.tar.xz
arm64: cpufeature: add HWCAP for FEAT_RPRES
Add a new HWCAP to detect the Increased precision of Reciprocal Estimate and Reciprocal Square Root Estimate feature (FEAT_RPRES), introduced in Armv8.7. Also expose this to userspace in the ID_AA64ISAR2_EL1 feature register. Signed-off-by: Joey Gouly <joey.gouly@arm.com> Cc: Will Deacon <will@kernel.org> Cc: Jonathan Corbet <corbet@lwn.net> Acked-by: Marc Zyngier <maz@kernel.org> Link: https://lore.kernel.org/r/20211210165432.8106-4-joey.gouly@arm.com Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Diffstat (limited to 'Documentation/arm64')
-rw-r--r--Documentation/arm64/cpu-feature-registers.rst8
-rw-r--r--Documentation/arm64/elf_hwcaps.rst4
2 files changed, 12 insertions, 0 deletions
diff --git a/Documentation/arm64/cpu-feature-registers.rst b/Documentation/arm64/cpu-feature-registers.rst
index 1b19d20c2dbd..749ae970c319 100644
--- a/Documentation/arm64/cpu-feature-registers.rst
+++ b/Documentation/arm64/cpu-feature-registers.rst
@@ -283,6 +283,14 @@ infrastructure:
| AFP | [47-44] | y |
+------------------------------+---------+---------+
+ 9) ID_AA64ISAR2_EL1 - Instruction set attribute register 2
+
+ +------------------------------+---------+---------+
+ | Name | bits | visible |
+ +------------------------------+---------+---------+
+ | RPRES | [7-4] | y |
+ +------------------------------+---------+---------+
+
Appendix I: Example
-------------------
diff --git a/Documentation/arm64/elf_hwcaps.rst b/Documentation/arm64/elf_hwcaps.rst
index 247728d37911..b72ff17d600a 100644
--- a/Documentation/arm64/elf_hwcaps.rst
+++ b/Documentation/arm64/elf_hwcaps.rst
@@ -255,6 +255,10 @@ HWCAP2_AFP
Functionality implied by ID_AA64MFR1_EL1.AFP == 0b0001.
+HWCAP2_RPRES
+
+ Functionality implied by ID_AA64ISAR2_EL1.RPRES == 0b0001.
+
4. Unused AT_HWCAP bits
-----------------------