RISC-V: split early & late of_node to hartid mapping

Some back and forth with Drew [1] about riscv_fill_hwcap() resulted in
the realisation that it is not very useful to parse the DT & perform
validation of riscv,isa every time we would like to get the id for a
hart.

Although it is no longer called in riscv_fill_hwcap(),
riscv_of_processor_hartid() is called in several other places.
Notably in setup_smp() it forms part of the logic for filling the mask
of possible CPUs. Since a possible CPU must have passed this basic
validation of riscv,isa, a repeat validation is not required.

Rename riscv_of_processor_id() to riscv_early_of_processor_id(),
which will be called from setup_smp() & introduce a new
riscv_of_processor_id() which makes use of the pre-populated mask of
possible cpus.

Link: https://lore.kernel.org/linux-riscv/xvdswl3iyikwvamny7ikrxo2ncuixshtg3f6uucjahpe3xpc5c@ud4cz4fkg5dj/ [1]
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
Reviewed-by: Sunil V L <sunilvl@ventanamicro.com>
Link: https://lore.kernel.org/r/20230607-glade-pastel-d8cbd9d9f3c6@spud
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

1 files changed, 21 insertions, 1 deletions

diff --git a/arch/riscv/kernel/cpu.c b/arch/riscv/kernel/cpu.c
index 637263f9a7b9..8025de06edb7 100644
--- a/arch/riscv/kernel/cpu.c
+++ b/arch/riscv/kernel/cpu.c
@@ -23,6 +23,26 @@
  */
 int riscv_of_processor_hartid(struct device_node *node, unsigned long *hart)
 {
+	int cpu;
+
+	*hart = (unsigned long)of_get_cpu_hwid(node, 0);
+	if (*hart == ~0UL) {
+		pr_warn("Found CPU without hart ID\n");
+		return -ENODEV;
+	}
+
+	cpu = riscv_hartid_to_cpuid(*hart);
+	if (cpu < 0)
+		return cpu;
+
+	if (!cpu_possible(cpu))
+		return -ENODEV;
+
+	return 0;
+}
+
+int riscv_early_of_processor_hartid(struct device_node *node, unsigned long *hart)
+{
 	const char *isa;
 
 	if (!of_device_is_compatible(node, "riscv")) {
@@ -30,7 +50,7 @@ int riscv_of_processor_hartid(struct device_node *node, unsigned long *hart)
 		return -ENODEV;
 	}
 
-	*hart = (unsigned long) of_get_cpu_hwid(node, 0);
+	*hart = (unsigned long)of_get_cpu_hwid(node, 0);
 	if (*hart == ~0UL) {
 		pr_warn("Found CPU without hart ID\n");
 		return -ENODEV;