linux-kernel - [PATCH v2] ARM : Support for optional ARMv8.2 half-precision floating point extension

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Date:   Mon, 12 Sep 2022 08:24:58 -0500
From:   george pee <georgepee@...il.com>
To:     unlisted-recipients:; (no To-header on input)
Cc:     george pee <georgepee@...il.com>,
        Russell King <linux@...linux.org.uk>,
        Ard Biesheuvel <ardb@...nel.org>,
        "Russell King (Oracle)" <rmk+kernel@...linux.org.uk>,
        Linus Walleij <linus.walleij@...aro.org>,
        Nicolas Pitre <nico@...xnic.net>,
        Keith Packard <keithpac@...zon.com>,
        Austin Kim <austindh.kim@...il.com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: [PATCH v2] ARM : Support for optional ARMv8.2 half-precision floating point extension

Report feature /proc/cpuinfo as fphp to be consistent with arm64

Signed-off-by: george pee <georgepee@...il.com>
---
 arch/arm/include/uapi/asm/hwcap.h | 1 +
 arch/arm/kernel/entry-armv.S      | 3 ++-
 arch/arm/kernel/setup.c           | 1 +
 arch/arm/vfp/vfpmodule.c          | 2 ++
 4 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/arch/arm/include/uapi/asm/hwcap.h b/arch/arm/include/uapi/asm/hwcap.h
index 990199d8b7c6..5d635dce8853 100644
--- a/arch/arm/include/uapi/asm/hwcap.h
+++ b/arch/arm/include/uapi/asm/hwcap.h
@@ -37,5 +37,6 @@
 #define HWCAP2_SHA1	(1 << 2)
 #define HWCAP2_SHA2	(1 << 3)
 #define HWCAP2_CRC32	(1 << 4)
+#define HWCAP2_FPHP	(1 << 5)
 
 #endif /* _UAPI__ASMARM_HWCAP_H */
diff --git a/arch/arm/kernel/entry-armv.S b/arch/arm/kernel/entry-armv.S
index c39303e5c234..161f8df852e1 100644
--- a/arch/arm/kernel/entry-armv.S
+++ b/arch/arm/kernel/entry-armv.S
@@ -625,11 +625,12 @@ call_fpe:
 	ret.w	lr				@ CP#6
 	ret.w	lr				@ CP#7
 	ret.w	lr				@ CP#8
-	ret.w	lr				@ CP#9
 #ifdef CONFIG_VFP
+	W(b)	do_vfp				@ CP#9  (VFP/FP16)
 	W(b)	do_vfp				@ CP#10 (VFP)
 	W(b)	do_vfp				@ CP#11 (VFP)
 #else
+	ret.w	lr				@ CP#9
 	ret.w	lr				@ CP#10 (VFP)
 	ret.w	lr				@ CP#11 (VFP)
 #endif
diff --git a/arch/arm/kernel/setup.c b/arch/arm/kernel/setup.c
index 1e8a50a97edf..8887d0f447d6 100644
--- a/arch/arm/kernel/setup.c
+++ b/arch/arm/kernel/setup.c
@@ -1258,6 +1258,7 @@ static const char *hwcap2_str[] = {
 	"sha1",
 	"sha2",
 	"crc32",
+	"fphp",
 	NULL
 };
 
diff --git a/arch/arm/vfp/vfpmodule.c b/arch/arm/vfp/vfpmodule.c
index 2cb355c1b5b7..0806b0b1f2c7 100644
--- a/arch/arm/vfp/vfpmodule.c
+++ b/arch/arm/vfp/vfpmodule.c
@@ -831,6 +831,8 @@ static int __init vfp_init(void)
 
 			if ((fmrx(MVFR1) & 0xf0000000) == 0x10000000)
 				elf_hwcap |= HWCAP_VFPv4;
+			if ((fmrx(MVFR1) & 0x0f000000) == 0x03000000)
+				elf_hwcap2 |= HWCAP2_FPHP;
 		}
 	/* Extract the architecture version on pre-cpuid scheme */
 	} else {
-- 
2.37.3