[PATCH v4 6/6] RISC-V: Improve /proc/cpuinfo output for ISA extensions

[Atish Patra]

Currently, the /proc/cpuinfo outputs the entire riscv,isa string which
is not ideal when we have multiple ISA extensions present in the ISA
string. Some of them may not be enabled in kernel as well.

Parse only the enabled ISA extension and print them in a separate row.

Signed-off-by: Atish Patra <atishp at rivosinc.com>
---
 arch/riscv/include/asm/hwcap.h |  7 ++++++
 arch/riscv/kernel/cpu.c        | 44 ++++++++++++++++++++++++++++++++--
 2 files changed, 49 insertions(+), 2 deletions(-)

diff --git a/arch/riscv/include/asm/hwcap.h b/arch/riscv/include/asm/hwcap.h
index 170bd80da520..691fc9c8099b 100644
--- a/arch/riscv/include/asm/hwcap.h
+++ b/arch/riscv/include/asm/hwcap.h
@@ -54,6 +54,13 @@ enum riscv_isa_ext_id {
 	RISCV_ISA_EXT_ID_MAX = RISCV_ISA_EXT_MAX,
 };
 
+struct riscv_isa_ext_data {
+	/* Name of the extension displayed to userspace via /proc/cpuinfo */
+	char uprop[RISCV_ISA_EXT_NAME_LEN_MAX];
+	/* The logical ISA extension ID */
+	unsigned int isa_ext_id;
+};
+
 unsigned long riscv_isa_extension_base(const unsigned long *isa_bitmap);
 
 #define riscv_isa_extension_mask(ext) BIT_MASK(RISCV_ISA_EXT_##ext)
diff --git a/arch/riscv/kernel/cpu.c b/arch/riscv/kernel/cpu.c
index ad0a7e9f828b..ced7e5be8641 100644
--- a/arch/riscv/kernel/cpu.c
+++ b/arch/riscv/kernel/cpu.c
@@ -6,6 +6,7 @@
 #include <linux/init.h>
 #include <linux/seq_file.h>
 #include <linux/of.h>
+#include <asm/hwcap.h>
 #include <asm/smp.h>
 #include <asm/pgtable.h>
 
@@ -63,12 +64,50 @@ int riscv_of_parent_hartid(struct device_node *node)
 }
 
 #ifdef CONFIG_PROC_FS
+#define __RISCV_ISA_EXT_DATA(UPROP, EXTID) \
+	{							\
+		.uprop = #UPROP,				\
+		.isa_ext_id = EXTID,				\
+	}
+
+static struct riscv_isa_ext_data isa_ext_arr[] = {
+	__RISCV_ISA_EXT_DATA("", RISCV_ISA_EXT_MAX),
+};
+
+static void print_isa_ext(struct seq_file *f)
+{
+	struct riscv_isa_ext_data *edata;
+	int i = 0, arr_sz;
+
+	arr_sz = ARRAY_SIZE(isa_ext_arr) - 1;
+
+	/* No extension support available */
+	if (arr_sz <= 0)
+		return;
+
+	seq_puts(f, "isa-ext\t\t: ");
+	for (i = 0; i <= arr_sz; i++) {
+		edata = &isa_ext_arr[i];
+		if (!__riscv_isa_extension_available(NULL, edata->isa_ext_id))
+			continue;
+		seq_printf(f, "%s ", edata->uprop);
+	}
+	seq_puts(f, "\n");
+}
 
 static void print_isa(struct seq_file *f, const char *isa)
 {
-	/* Print the entire ISA as it is */
+	char *ext_start;
+	int isa_len = strlen(isa);
+	int base_isa_len = isa_len;
+
+	ext_start = strnchr(isa, isa_len, '_');
+	if (ext_start)
+		base_isa_len = isa_len - strlen(ext_start);
+
+	/* Print only the base ISA as it is */
 	seq_puts(f, "isa\t\t: ");
-	seq_write(f, isa, strlen(isa));
+	seq_write(f, isa, base_isa_len);
 	seq_puts(f, "\n");
 }
 
@@ -115,6 +154,7 @@ static int c_show(struct seq_file *m, void *v)
 	seq_printf(m, "hart\t\t: %lu\n", cpuid_to_hartid_map(cpu_id));
 	if (!of_property_read_string(node, "riscv,isa", &isa))
 		print_isa(m, isa);
+	print_isa_ext(m);
 	print_mmu(m);
 	if (!of_property_read_string(node, "compatible", &compat)
 	    && strcmp(compat, "riscv"))
-- 
2.30.2