[PATCH -next v17 07/20] riscv: Introduce riscv_v_vsize to record size of Vector context

[Andy Chiu <andy.chiu@xxxxxxxxxx>]

From: Greentime Hu <greentime.hu@xxxxxxxxxx>

This patch is used to detect the size of CPU vector registers and use
riscv_v_vsize to save the size of all the vector registers. It assumes all
harts has the same capabilities in a SMP system.

Co-developed-by: Guo Ren <guoren@xxxxxxxxxxxxxxxxx>
Signed-off-by: Guo Ren <guoren@xxxxxxxxxxxxxxxxx>
Co-developed-by: Vincent Chen <vincent.chen@xxxxxxxxxx>
Signed-off-by: Vincent Chen <vincent.chen@xxxxxxxxxx>
Signed-off-by: Greentime Hu <greentime.hu@xxxxxxxxxx>
Signed-off-by: Andy Chiu <andy.chiu@xxxxxxxxxx>
Reviewed-by: Conor Dooley <conor.dooley@xxxxxxxxxxxxx>
---
 arch/riscv/include/asm/vector.h |  5 +++++
 arch/riscv/kernel/Makefile      |  1 +
 arch/riscv/kernel/cpufeature.c  |  2 ++
 arch/riscv/kernel/vector.c      | 20 ++++++++++++++++++++
 4 files changed, 28 insertions(+)
 create mode 100644 arch/riscv/kernel/vector.c

diff --git a/arch/riscv/include/asm/vector.h b/arch/riscv/include/asm/vector.h
index dfe5a321b2b4..e433ba3cd4da 100644
--- a/arch/riscv/include/asm/vector.h
+++ b/arch/riscv/include/asm/vector.h
@@ -13,6 +13,9 @@
 #include <asm/hwcap.h>
 #include <asm/csr.h>
 
+extern unsigned long riscv_v_vsize;
+void riscv_v_setup_vsize(void);
+
 static __always_inline bool has_vector(void)
 {
 	return riscv_has_extension_likely(RISCV_ISA_EXT_v);
@@ -31,6 +34,8 @@ static __always_inline void riscv_v_disable(void)
 #else /* ! CONFIG_RISCV_ISA_V  */
 
 static __always_inline bool has_vector(void) { return false; }
+#define riscv_v_vsize (0)
+#define riscv_v_setup_vsize()			do {} while (0)
 
 #endif /* CONFIG_RISCV_ISA_V */
 
diff --git a/arch/riscv/kernel/Makefile b/arch/riscv/kernel/Makefile
index 392fa6e35d4a..be23a021ec32 100644
--- a/arch/riscv/kernel/Makefile
+++ b/arch/riscv/kernel/Makefile
@@ -55,6 +55,7 @@ obj-$(CONFIG_MMU) += vdso.o vdso/
 
 obj-$(CONFIG_RISCV_M_MODE)	+= traps_misaligned.o
 obj-$(CONFIG_FPU)		+= fpu.o
+obj-$(CONFIG_RISCV_ISA_V)	+= vector.o
 obj-$(CONFIG_SMP)		+= smpboot.o
 obj-$(CONFIG_SMP)		+= smp.o
 obj-$(CONFIG_SMP)		+= cpu_ops.o
diff --git a/arch/riscv/kernel/cpufeature.c b/arch/riscv/kernel/cpufeature.c
index 923ca75f2192..267070f3cc9e 100644
--- a/arch/riscv/kernel/cpufeature.c
+++ b/arch/riscv/kernel/cpufeature.c
@@ -17,6 +17,7 @@
 #include <asm/hwcap.h>
 #include <asm/patch.h>
 #include <asm/processor.h>
+#include <asm/vector.h>
 
 #define NUM_ALPHA_EXTS ('z' - 'a' + 1)
 
@@ -263,6 +264,7 @@ void __init riscv_fill_hwcap(void)
 	}
 
 	if (elf_hwcap & COMPAT_HWCAP_ISA_V) {
+		riscv_v_setup_vsize();
 		/*
 		 * ISA string in device tree might have 'v' flag, but
 		 * CONFIG_RISCV_ISA_V is disabled in kernel.
diff --git a/arch/riscv/kernel/vector.c b/arch/riscv/kernel/vector.c
new file mode 100644
index 000000000000..03582e2ade83
--- /dev/null
+++ b/arch/riscv/kernel/vector.c
@@ -0,0 +1,20 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (C) 2023 SiFive
+ * Author: Andy Chiu <andy.chiu@xxxxxxxxxx>
+ */
+#include <linux/export.h>
+
+#include <asm/vector.h>
+#include <asm/csr.h>
+
+unsigned long riscv_v_vsize __read_mostly;
+EXPORT_SYMBOL_GPL(riscv_v_vsize);
+
+void riscv_v_setup_vsize(void)
+{
+	/* There are 32 vector registers with vlenb length. */
+	riscv_v_enable();
+	riscv_v_vsize = csr_read(CSR_VLENB) * 32;
+	riscv_v_disable();
+}
-- 
2.17.1