riscv: allow case-insensitive ISA string parsing

According to RISC-V Hart Capabilities Table (RHCT) description in UEFI
Forum ECR, the format of the ISA string is defined in the RISC-V
unprivileged specification which is case-insensitive. However, the
current ISA string parser in the kernel does not support ISA strings
with uppercase letters.

This patch modifies the ISA string parser in the kernel to support
case-insensitive ISA string parsing.

Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Signed-off-by: Yangyu Chen <cyy@cyyself.name>
Link: https://lore.kernel.org/r/tencent_B30EED51C7235CA1988890E5C658BE35C107@qq.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

Author: cyyself

arch/riscv/kernel/cpu.c

@@ -4,6 +4,7 @@
  */
 
 #include <linux/cpu.h>
+#include <linux/ctype.h>
 #include <linux/init.h>
 #include <linux/seq_file.h>
 #include <linux/of.h>
@@ -42,7 +43,7 @@ int riscv_of_processor_hartid(struct device_node *node, unsigned long *hart)
 		pr_warn("CPU with hartid=%lu has no \"riscv,isa\" property\n", *hart);
 		return -ENODEV;
 	}
-	if (isa[0] != 'r' || isa[1] != 'v') {
+	if (tolower(isa[0]) != 'r' || tolower(isa[1]) != 'v') {
 		pr_warn("CPU with hartid=%lu has an invalid ISA of \"%s\"\n", *hart, isa);
 		return -ENODEV;
 	}

arch/riscv/kernel/cpufeature.c

@@ -127,13 +127,10 @@ void __init riscv_fill_hwcap(void)
 		}
 
 		temp = isa;
-#if IS_ENABLED(CONFIG_32BIT)
-		if (!strncmp(isa, "rv32", 4))
+		if (IS_ENABLED(CONFIG_32BIT) && !strncasecmp(isa, "rv32", 4))
 			isa += 4;
-#elif IS_ENABLED(CONFIG_64BIT)
-		if (!strncmp(isa, "rv64", 4))
+		else if (IS_ENABLED(CONFIG_64BIT) && !strncasecmp(isa, "rv64", 4))
 			isa += 4;
-#endif
 		/* The riscv,isa DT property must start with rv64 or rv32 */
 		if (temp == isa)
 			continue;
@@ -157,13 +154,15 @@ void __init riscv_fill_hwcap(void)
 					break;
 				}
 				fallthrough;
+			case 'S':
 			case 'x':
+			case 'X':
 			case 'z':
+			case 'Z':
 				ext_long = true;
 				/* Multi-letter extension must be delimited */
 				for (; *isa && *isa != '_'; ++isa)
-					if (unlikely(!islower(*isa)
-						     && !isdigit(*isa)))
+					if (unlikely(!isalnum(*isa)))
 						ext_err = true;
 				/* Parse backwards */
 				ext_end = isa;
@@ -174,7 +173,7 @@ void __init riscv_fill_hwcap(void)
 				/* Skip the minor version */
 				while (isdigit(*--ext_end))
 					;
-				if (ext_end[0] != 'p'
+				if (tolower(ext_end[0]) != 'p'
 				    || !isdigit(ext_end[-1])) {
 					/* Advance it to offset the pre-decrement */
 					++ext_end;
@@ -186,7 +185,7 @@ void __init riscv_fill_hwcap(void)
 				++ext_end;
 				break;
 			default:
-				if (unlikely(!islower(*ext))) {
+				if (unlikely(!isalpha(*ext))) {
 					ext_err = true;
 					break;
 				}
@@ -196,7 +195,7 @@ void __init riscv_fill_hwcap(void)
 				/* Skip the minor version */
 				while (isdigit(*++isa))
 					;
-				if (*isa != 'p')
+				if (tolower(*isa) != 'p')
 					break;
 				if (!isdigit(*++isa)) {
 					--isa;
@@ -210,18 +209,18 @@ void __init riscv_fill_hwcap(void)
 			if (*isa != '_')
 				--isa;
 
-#define SET_ISA_EXT_MAP(name, bit)						\
-			do {							\
-				if ((ext_end - ext == sizeof(name) - 1) &&	\
-				     !memcmp(ext, name, sizeof(name) - 1) &&	\
-				     riscv_isa_extension_check(bit))		\
-					set_bit(bit, this_isa);			\
-			} while (false)						\
+#define SET_ISA_EXT_MAP(name, bit)							\
+			do {								\
+				if ((ext_end - ext == sizeof(name) - 1) &&		\
+				     !strncasecmp(ext, name, sizeof(name) - 1) &&	\
+				     riscv_isa_extension_check(bit))			\
+					set_bit(bit, this_isa);				\
+			} while (false)							\
 
 			if (unlikely(ext_err))
 				continue;
 			if (!ext_long) {
-				int nr = *ext - 'a';
+				int nr = tolower(*ext) - 'a';
 
 				if (riscv_isa_extension_check(nr)) {
 					this_hwcap |= isa2hwcap[nr];