ARM: 9270/1: vfp: Add hwcap for FEAT_FHM

Floating-point half-precision multiplication (FHM) is a feature present
in AArch32 state for Armv8 and is represented by ISAR6.FHM identification register.

This feature denotes the presence of VFMAL and VMFSL instructions and
hence adding a hwcap will enable the userspace to check it before
trying to use those instructions.
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Amit Daniel Kachhap <amit.kachhap@arm.com>
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>

arch/arm/include/uapi/asm/hwcap.h

@@ -31,6 +31,7 @@
 #define HWCAP_FPHP	(1 << 22)
 #define HWCAP_ASIMDHP	(1 << 23)
 #define HWCAP_ASIMDDP	(1 << 24)
+#define HWCAP_ASIMDFHM	(1 << 25)
 
 /*
  * HWCAP2 flags - for elf_hwcap2 (in kernel) and AT_HWCAP2

arch/arm/kernel/setup.c

@@ -1252,6 +1252,7 @@ static const char *hwcap_str[] = {
 	"fphp",
 	"asimdhp",
 	"asimddp",
+	"asimdfhm",
 	NULL
 };
 

arch/arm/vfp/vfpmodule.c

@@ -845,6 +845,12 @@ static int __init vfp_init(void)
 		isar6 = read_cpuid_ext(CPUID_EXT_ISAR6);
 		if (cpuid_feature_extract_field(isar6, 4) == 0x1)
 			elf_hwcap |= HWCAP_ASIMDDP;
+		/*
+		 * Check for the presence of Advanced SIMD Floating point
+		 * half-precision multiplication instructions.
+		 */
+		if (cpuid_feature_extract_field(isar6, 8) == 0x1)
+			elf_hwcap |= HWCAP_ASIMDFHM;
 
 	/* Extract the architecture version on pre-cpuid scheme */
 	} else {