arm64: Add compat hwcap ASIMDBF16

This hwcap was added earlier for 32-bit native arm kernel by commit
23b6d4ad ("ARM: 9271/1: vfp: Add hwcap for FEAT_AA32BF16") and hence
the corresponding changes added in 32-bit compat arm64 kernel.

Brain 16-bit floating-point storage format is a feature (FEAT_AA32BF16)
present in AArch32 state for Armv8 and is represented by ISAR6.BF16
identification register. Similar feature (FEAT_BF16) exist for AArch64
state and is already advertised in native arm64 kernel.
Signed-off-by: Amit Daniel Kachhap <amit.kachhap@arm.com>
Reviewed-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20230111053706.13994-5-amit.kachhap@arm.comSigned-off-by: Catalin Marinas <catalin.marinas@arm.com>

arch/arm64/include/asm/hwcap.h

@@ -35,6 +35,7 @@
 #define COMPAT_HWCAP_ASIMDHP	(1 << 23)
 #define COMPAT_HWCAP_ASIMDDP	(1 << 24)
 #define COMPAT_HWCAP_ASIMDFHM	(1 << 25)
+#define COMPAT_HWCAP_ASIMDBF16	(1 << 26)
 
 #define COMPAT_HWCAP2_AES	(1 << 0)
 #define COMPAT_HWCAP2_PMULL	(1 << 1)

arch/arm64/kernel/cpufeature.c

@@ -530,7 +530,7 @@ static const struct arm64_ftr_bits ftr_id_mmfr5[] = {
 
 static const struct arm64_ftr_bits ftr_id_isar6[] = {
 	ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, ID_ISAR6_EL1_I8MM_SHIFT, 4, 0),
-	ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, ID_ISAR6_EL1_BF16_SHIFT, 4, 0),
+	ARM64_FTR_BITS(FTR_VISIBLE, FTR_STRICT, FTR_LOWER_SAFE, ID_ISAR6_EL1_BF16_SHIFT, 4, 0),
 	ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, ID_ISAR6_EL1_SPECRES_SHIFT, 4, 0),
 	ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, ID_ISAR6_EL1_SB_SHIFT, 4, 0),
 	ARM64_FTR_BITS(FTR_VISIBLE, FTR_STRICT, FTR_LOWER_SAFE, ID_ISAR6_EL1_FHM_SHIFT, 4, 0),
@@ -2875,6 +2875,7 @@ static const struct arm64_cpu_capabilities compat_elf_hwcaps[] = {
 	HWCAP_CAP(SYS_ID_ISAR5_EL1, ID_ISAR5_EL1_CRC32_SHIFT, 4, FTR_UNSIGNED, 1, CAP_COMPAT_HWCAP2, COMPAT_HWCAP2_CRC32),
 	HWCAP_CAP(SYS_ID_ISAR6_EL1, ID_ISAR6_EL1_DP_SHIFT, 4, FTR_UNSIGNED, 1, CAP_COMPAT_HWCAP, COMPAT_HWCAP_ASIMDDP),
 	HWCAP_CAP(SYS_ID_ISAR6_EL1, ID_ISAR6_EL1_FHM_SHIFT, 4, FTR_UNSIGNED, 1, CAP_COMPAT_HWCAP, COMPAT_HWCAP_ASIMDFHM),
+	HWCAP_CAP(SYS_ID_ISAR6_EL1, ID_ISAR6_EL1_BF16_SHIFT, 4, FTR_UNSIGNED, 1, CAP_COMPAT_HWCAP, COMPAT_HWCAP_ASIMDBF16),
 #endif
 	{},
 };

arch/arm64/kernel/cpuinfo.c

@@ -150,6 +150,7 @@ static const char *const compat_hwcap_str[] = {
 	[COMPAT_KERNEL_HWCAP(ASIMDHP)]	= "asimdhp",
 	[COMPAT_KERNEL_HWCAP(ASIMDDP)]	= "asimddp",
 	[COMPAT_KERNEL_HWCAP(ASIMDFHM)]	= "asimdfhm",
+	[COMPAT_KERNEL_HWCAP(ASIMDBF16)] = "asimdbf16",
 };
 
 #define COMPAT_KERNEL_HWCAP2(x)	const_ilog2(COMPAT_HWCAP2_ ## x)