lib: utils/fdt: Add support for parsing riscv,isa-extensions

A new property has been added, with an extensive rationale at [1], that
can be used in place of "riscv,isa" to indicate what extensions are
supported by a given platform that is a list of strings rather than a
single string. There are some differences between the new property,
"riscv,isa-extensions" and the incumbent "riscv,isa" - chief among them
for the sake of parsing being the list of strings, as opposed to a
string. Another advantage is strictly defined meanings for each string
in a dt-binding, rather than deriving meaning from RVI standards. This
may likely to some divergence over time, but, at least for now, there's
no relevant differences between the two for an M-Mode program.

Add support for the new property in OpenSBI, prioritising it, before
falling back to the, now deprecated, "riscv,isa" property if it is not
present.

Link: https://lore.kernel.org/all/20230702-eats-scorebook-c951f170d29f@spud/ [1]
Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
Reviewed-by: Anup Patel <anup@brainfault.org>

1 files changed, 23 insertions, 4 deletions

diff --git a/lib/utils/fdt/fdt_helper.c b/lib/utils/fdt/fdt_helper.c
index 9a945af..b7f7e07 100644
--- a/lib/utils/fdt/fdt_helper.c
+++ b/lib/utils/fdt/fdt_helper.c
@@ -411,6 +411,18 @@ static int fdt_parse_isa_one_hart(const char *isa, unsigned long *extensions)
 	return 0;
 }
 
+static void fdt_parse_isa_extensions_one_hart(const char *isa,
+					      unsigned long *extensions,
+					      int len)
+{
+	size_t i;
+
+	for (i = 0; i < SBI_HART_EXT_MAX; i++) {
+		if (fdt_stringlist_contains(isa, len, sbi_hart_ext[i].name))
+			__set_bit(sbi_hart_ext[i].id, extensions);
+	}
+}
+
 static int fdt_parse_isa_all_harts(void *fdt)
 {
 	u32 hartid;
@@ -434,10 +446,6 @@ static int fdt_parse_isa_all_harts(void *fdt)
 		if (!fdt_node_is_enabled(fdt, cpu_offset))
 			continue;
 
-		val = fdt_getprop(fdt, cpu_offset, "riscv,isa", &len);
-		if (!val || len <= 0)
-			return SBI_ENOENT;
-
 		scratch = sbi_hartid_to_scratch(hartid);
 		if (!scratch)
 			return SBI_ENOENT;
@@ -445,6 +453,17 @@ static int fdt_parse_isa_all_harts(void *fdt)
 		hart_exts = sbi_scratch_offset_ptr(scratch,
 						   fdt_isa_bitmap_offset);
 
+		val = fdt_getprop(fdt, cpu_offset, "riscv,isa-extensions", &len);
+		if (val && len > 0) {
+			fdt_parse_isa_extensions_one_hart((const char *)val,
+							  hart_exts, len);
+			continue;
+		}
+
+		val = fdt_getprop(fdt, cpu_offset, "riscv,isa", &len);
+		if (!val || len <= 0)
+			return SBI_ENOENT;
+
 		err = fdt_parse_isa_one_hart((const char *)val, hart_exts);
 		if (err)
 			return err;