ARM: 9269/1: vfp: Add hwcap for FEAT_DotProd

Advanced Dot product is a feature present in AArch32 state for Armv8 and
is represented by ISAR6 identification register.

This feature denotes the presence of UDOT and SDOT 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

@@ -30,6 +30,7 @@
 #define HWCAP_EVTSTRM	(1 << 21)
 #define HWCAP_FPHP	(1 << 22)
 #define HWCAP_ASIMDHP	(1 << 23)
+#define HWCAP_ASIMDDP	(1 << 24)
 
 /*
  * HWCAP2 flags - for elf_hwcap2 (in kernel) and AT_HWCAP2

arch/arm/kernel/setup.c

@@ -1251,6 +1251,7 @@ static const char *hwcap_str[] = {
 	"evtstrm",
 	"fphp",
 	"asimdhp",
+	"asimddp",
 	NULL
 };
 

arch/arm/vfp/vfpmodule.c

@@ -774,6 +774,7 @@ static int __init vfp_init(void)
 {
 	unsigned int vfpsid;
 	unsigned int cpu_arch = cpu_architecture();
+	unsigned int isar6;
 
 	/*
 	 * Enable the access to the VFP on all online CPUs so the
@@ -836,6 +837,15 @@ static int __init vfp_init(void)
 			if (((fmrx(MVFR1) & MVFR1_FPHP_MASK) >> MVFR1_FPHP_BIT) == 0x3)
 				elf_hwcap |= HWCAP_FPHP;
 		}
+
+		/*
+		 * Check for the presence of Advanced SIMD Dot Product
+		 * instructions.
+		 */
+		isar6 = read_cpuid_ext(CPUID_EXT_ISAR6);
+		if (cpuid_feature_extract_field(isar6, 4) == 0x1)
+			elf_hwcap |= HWCAP_ASIMDDP;
+
 	/* Extract the architecture version on pre-cpuid scheme */
 	} else {
 		if (vfpsid & FPSID_NODOUBLE) {