Merge patch series "riscv: allow case-insensitive ISA string parsing"

Yangyu Chen <cyy@cyyself.name> says:

This patchset allows case-insensitive ISA string parsing, which is
needed in the ACPI environment. As the RISC-V Hart Capabilities Table
(RHCT) description in UEFI Forum ECR[1] shows the format of the ISA
string is defined in the RISC-V unprivileged specification[2]. However,
the RISC-V unprivileged specification defines the ISA naming strings are
case-insensitive while the current ISA string parser in the kernel only
accepts lowercase letters. In this case, the kernel should allow
case-insensitive ISA string parsing. Moreover, this reason has been
discussed in Conor's patch[3]. And I have also checked the current ISA
string parsing in the recent ACPI support patch[4] will also call
`riscv_fill_hwcap` function as DT we use now.

The original motivation for my patch v1[5] is that some SoC generators
will provide generated DT with illegal ISA string in dt-binding such as
rocket-chip, which will even cause kernel panic in some cases as I
mentioned in v1[5]. Now, the rocket-chip has been fixed in PR #3333[6].
However, when using some specific version of rocket-chip with
illegal ISA string in DT, this patchset will also work for parsing
uppercase letters correctly in DT, thus will have better compatibility.

In summary, this patch not only works for case-insensitive ISA string
parsing to meet the requirements in ECR[1] but also can be a workaround
for some specific versions of rocket-chip.

* b4-shazam-merge:
  dt-bindings: riscv: drop invalid comment about riscv,isa lower-case reasoning
  riscv: allow case-insensitive ISA string parsing

Link: https://lore.kernel.org/r/tencent_E6911C8D71F5624E432A1AFDF86804C3B509@qq.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

1 files changed, 2 insertions, 1 deletions

diff --git a/arch/riscv/kernel/cpu.c b/arch/riscv/kernel/cpu.c
index 5de6fb703cc2..637263f9a7b9 100644
--- a/arch/riscv/kernel/cpu.c
+++ b/arch/riscv/kernel/cpu.c
@@ -5,6 +5,7 @@
 
 #include <linux/acpi.h>
 #include <linux/cpu.h>
+#include <linux/ctype.h>
 #include <linux/init.h>
 #include <linux/seq_file.h>
 #include <linux/of.h>
@@ -44,7 +45,7 @@ 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;
 	}