[PATCH v2 4/8] RISC-V: validate riscv,isa at boot, not during ISA string parsing

[Conor Dooley <conor@kernel.org>]

From: Conor Dooley <conor.dooley@microchip.com>

Since riscv_fill_hwcap() now only iterates over possible cpus, the
basic validation of whether riscv,isa contains "rv<width>" can be moved
to riscv_early_of_processor_hartid().

Further, "ima" support is required by the kernel, so reject any CPU not
fitting the bill.

Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
---
 arch/riscv/kernel/cpu.c        |  8 +++++---
 arch/riscv/kernel/cpufeature.c | 12 ++++++------
 2 files changed, 11 insertions(+), 9 deletions(-)

diff --git a/arch/riscv/kernel/cpu.c b/arch/riscv/kernel/cpu.c
index 7030a5004f8e..b0c3ec0f2f5b 100644
--- a/arch/riscv/kernel/cpu.c
+++ b/arch/riscv/kernel/cpu.c
@@ -63,10 +63,12 @@ int riscv_early_of_processor_hartid(struct device_node *node, unsigned long *har
 		pr_warn("CPU with hartid=%lu has no \"riscv,isa\" property\n", *hart);
 		return -ENODEV;
 	}
-	if (tolower(isa[0]) != 'r' || tolower(isa[1]) != 'v') {
-		pr_warn("CPU with hartid=%lu has an invalid ISA of \"%s\"\n", *hart, isa);
+
+	if (IS_ENABLED(CONFIG_32BIT) && strncasecmp(isa, "rv32ima", 7))
+		return -ENODEV;
+
+	if (IS_ENABLED(CONFIG_64BIT) && strncasecmp(isa, "rv64ima", 7))
 		return -ENODEV;
-	}
 
 	return 0;
 }
diff --git a/arch/riscv/kernel/cpufeature.c b/arch/riscv/kernel/cpufeature.c
index 3ae456413f79..a79c5c52a174 100644
--- a/arch/riscv/kernel/cpufeature.c
+++ b/arch/riscv/kernel/cpufeature.c
@@ -130,12 +130,12 @@ void __init riscv_fill_hwcap(void)
 			continue;
 		}
 
-		if (IS_ENABLED(CONFIG_32BIT) && strncasecmp(isa, "rv32", 4))
-			continue;
-
-		if (IS_ENABLED(CONFIG_64BIT) && strncasecmp(isa, "rv64", 4))
-			continue;
-
+		/*
+		 * For all possible cpus, we have already validated in
+		 * the boot process that they at least contain "rv" and
+		 * whichever of "32"/"64" this kernel supports, and so this
+		 * section can be skipped.
+		 */
 		isa += 4;
 
 		bitmap_zero(this_isa, RISCV_ISA_EXT_MAX);
-- 
2.39.2