[PATCH 2/3] RISC-V: Add T-Head 0.7.1 vector extension to hwprobe

[Charlie Jenkins]

Using vendor extensions in hwprobe, add the ability to query if the
0.7.1 vector extension is available. It is determined to be available
only if the kernel is compiled with vector support, and the user is
using the c906.

Signed-off-by: Charlie Jenkins <charlie at rivosinc.com>
---
 arch/riscv/Kconfig.vendor                       | 11 +++++++++++
 arch/riscv/include/asm/extensions.h             | 16 ++++++++++++++++
 arch/riscv/kernel/sys_riscv.c                   | 20 ++++++++++++++++++++
 arch/riscv/vendor_extensions/Makefile           |  2 ++
 arch/riscv/vendor_extensions/thead/Makefile     |  8 ++++++++
 arch/riscv/vendor_extensions/thead/extensions.c | 24 ++++++++++++++++++++++++
 6 files changed, 81 insertions(+)

diff --git a/arch/riscv/Kconfig.vendor b/arch/riscv/Kconfig.vendor
index 213ac3e6fed5..b8b9d15153eb 100644
--- a/arch/riscv/Kconfig.vendor
+++ b/arch/riscv/Kconfig.vendor
@@ -1,3 +1,14 @@
 menu "Vendor extensions selection"
 
+config VENDOR_EXTENSIONS_THEAD
+	bool "T-HEAD vendor extensions"
+	depends on RISCV_ALTERNATIVE
+	default n
+	help
+	  All T-HEAD vendor extensions Kconfig depend on this Kconfig. Disabling
+	  this Kconfig will disable all T-HEAD vendor extensions. Please say "Y"
+	  here if your platform uses T-HEAD vendor extensions.
+
+	  Otherwise, please say "N" here to avoid unnecessary overhead.
+
 endmenu # "Vendor extensions selection"
diff --git a/arch/riscv/include/asm/extensions.h b/arch/riscv/include/asm/extensions.h
new file mode 100644
index 000000000000..27ce294a3d65
--- /dev/null
+++ b/arch/riscv/include/asm/extensions.h
@@ -0,0 +1,16 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (C) 2023 by Rivos Inc.
+ */
+#ifndef __ASM_EXTENSIONS_H
+#define __ASM_EXTENSIONS_H
+
+#include <asm/hwprobe.h>
+#include <linux/cpumask.h>
+
+#define THEAD_ISA_EXT0 (RISCV_HWPROBE_VENDOR_EXTENSION_SPACE)
+#define THEAD_ISA_EXT0_V0_7_1 (1 << 0)
+
+int hwprobe_thead(__u64 marchid, __u64 mimpid, struct riscv_hwprobe *pair,
+		  const struct cpumask *cpus);
+#endif
diff --git a/arch/riscv/kernel/sys_riscv.c b/arch/riscv/kernel/sys_riscv.c
index 2351a5f7b8b1..58b12eaeaf46 100644
--- a/arch/riscv/kernel/sys_riscv.c
+++ b/arch/riscv/kernel/sys_riscv.c
@@ -13,6 +13,7 @@
 #include <asm/vector.h>
 #include <asm/switch_to.h>
 #include <asm/uaccess.h>
+#include <asm/extensions.h>
 #include <asm/unistd.h>
 #include <asm-generic/mman-common.h>
 #include <vdso/vsyscall.h>
@@ -192,6 +193,25 @@ static int hwprobe_vendor(__u64 mvendorid, struct riscv_hwprobe *pair,
 			 const struct cpumask *cpus)
 {
 	switch (mvendorid) {
+#ifdef CONFIG_VENDOR_EXTENSIONS_THEAD
+	case THEAD_VENDOR_ID:
+		struct riscv_hwprobe marchid = {
+			.key = RISCV_HWPROBE_KEY_MARCHID,
+			.value = 0
+		};
+		struct riscv_hwprobe mimpid = {
+			.key = RISCV_HWPROBE_KEY_MIMPID,
+			.value = 0
+		};
+
+		hwprobe_arch_id(&marchid, cpus);
+		hwprobe_arch_id(&mimpid, cpus);
+		if (marchid.value != -1ULL && mimpid.value != -1ULL)
+			hwprobe_thead(marchid.value, mimpid.value, pair, cpus);
+		else
+			return -1;
+		break;
+#endif
 	default:
 		return -1;
 	}
diff --git a/arch/riscv/vendor_extensions/Makefile b/arch/riscv/vendor_extensions/Makefile
index e815895e9372..38c3e80469fd 100644
--- a/arch/riscv/vendor_extensions/Makefile
+++ b/arch/riscv/vendor_extensions/Makefile
@@ -1,3 +1,5 @@
 ifdef CONFIG_RELOCATABLE
 KBUILD_CFLAGS += -fno-pie
 endif
+
+obj-$(CONFIG_VENDOR_EXTENSIONS_THEAD) += thead/
diff --git a/arch/riscv/vendor_extensions/thead/Makefile b/arch/riscv/vendor_extensions/thead/Makefile
new file mode 100644
index 000000000000..7cf43c629b66
--- /dev/null
+++ b/arch/riscv/vendor_extensions/thead/Makefile
@@ -0,0 +1,8 @@
+ifdef CONFIG_FTRACE
+CFLAGS_REMOVE_extensions.o = $(CC_FLAGS_FTRACE)
+endif
+ifdef CONFIG_KASAN
+KASAN_SANITIZE_extensions.o := n
+endif
+
+obj-y += extensions.o
diff --git a/arch/riscv/vendor_extensions/thead/extensions.c b/arch/riscv/vendor_extensions/thead/extensions.c
new file mode 100644
index 000000000000..a177501bc99c
--- /dev/null
+++ b/arch/riscv/vendor_extensions/thead/extensions.c
@@ -0,0 +1,24 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2023 by Rivos Inc.
+ */
+
+#include <asm/extensions.h>
+
+int hwprobe_thead(__u64 marchid, __u64 mimpid, struct riscv_hwprobe *pair,
+		  const struct cpumask *cpus)
+{
+	pair->value = 0;
+	switch (pair->key) {
+	case THEAD_ISA_EXT0:
+#ifdef CONFIG_RISCV_ISA_V
+		if (marchid == 0 && mimpid == 0)
+			pair->value |= THEAD_ISA_EXT0_V0_7_1;
+#endif
+		break;
+	default:
+		return -1;
+	}
+
+	return 0;
+}

-- 
2.41.0