RISC-V: Improve /proc/cpuinfo output for ISA extensions

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.
Same goes for the single letter extensions as well which prints the
entire ISA string. Some of they may not be valid ISA extensions as
well (e.g 'su')

Parse only the valid & enabled ISA extension and print them.

Tested-by: Heiko Stuebner <heiko@sntech.de>
Signed-off-by: Atish Patra <atishp@rivosinc.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

diff --git a/arch/riscv/include/asm/hwcap.h b/arch/riscv/include/asm/hwcap.h
index 170bd80da520544b7c32a9429605e6701e3d15d2..691fc9c8099b6f6150d3f65578d1522ea518f4b4 100644 (file)
--- 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 ad0a7e9f828bef4806febe956ba3ef3875486722..fc115e307ef57f60fbd1df6980226c0f9f82cfd1 100644 (file)
--- 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 +64,72 @@ 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,                            \
+       }
+/**
+ * Here are the ordering rules of extension naming defined by RISC-V
+ * specification :
+ * 1. All extensions should be separated from other multi-letter extensions
+ *    from other multi-letter extensions by an underscore.
+ * 2. The first letter following the 'Z' conventionally indicates the most
+ *    closely related alphabetical extension category, IMAFDQLCBKJTPVH.
+ *    If multiple 'Z' extensions are named, they should be ordered first
+ *    by category, then alphabetically within a category.
+ * 3. Standard supervisor-level extensions (starts with 'S') should be
+ *    listed after standard unprivileged extensions.  If multiple
+ *    supervisor-level extensions are listed, they should be ordered
+ *    alphabetically.
+ * 4. Non-standard extensions (starts with 'X') must be listed after all
+ *    standard extensions. They must be separated from other multi-letter
+ *    extensions by an underscore.
+ */
+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;
+
+       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);
+       }
+}
+
+/**
+ * These are the only valid base (single letter) ISA extensions as per the spec.
+ * It also specifies the canonical order in which it appears in the spec.
+ * Some of the extension may just be a place holder for now (B, K, P, J).
+ * This should be updated once corresponding extensions are ratified.
+ */
+static const char base_riscv_exts[13] = "imafdqcbkjpvh";
 
 static void print_isa(struct seq_file *f, const char *isa)
 {
-       /* Print the entire ISA as it is */
+       int i;
+
        seq_puts(f, "isa\t\t: ");
-       seq_write(f, isa, strlen(isa));
+       /* Print the rv[64/32] part */
+       seq_write(f, isa, 4);
+       for (i = 0; i < sizeof(base_riscv_exts); i++) {
+               if (__riscv_isa_extension_available(NULL, base_riscv_exts[i] - 'a'))
+                       /* Print only enabled the base ISA extensions */
+                       seq_write(f, &base_riscv_exts[i], 1);
+       }
+       print_isa_ext(f);
        seq_puts(f, "\n");
 }