riscv: Prevent a bad reference count on CPU nodes

When populating cache leaves we previously fetched the CPU device node
at the very beginning. But when ACPI is enabled we go through a
specific branch which returns early and does not call 'of_node_put' for
the node that was acquired.

Since we are not using a CPU device node for the ACPI code anyways, we
can simply move the initialization of it just passed the ACPI block, and
we are guaranteed to have an 'of_node_put' call for the acquired node.
This prevents a bad reference count of the CPU device node.

Moreover, the previous function did not check for errors when acquiring
the device node, so a return -ENOENT has been added for that case.

Signed-off-by: Miquel Sabaté Solà <mikisabate@gmail.com>
Reviewed-by: Sudeep Holla <sudeep.holla@arm.com>
Reviewed-by: Sunil V L <sunilvl@ventanamicro.com>
Reviewed-by: Alexandre Ghiti <alexghiti@rivosinc.com>
Fixes: 604f32e ("riscv: cacheinfo: initialize cacheinfo's level and  type from ACPI PPTT")
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20240913080053.36636-1-mikisabate@gmail.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

Author: mssola

arch/riscv/kernel/cacheinfo.c

@@ -80,8 +80,7 @@ int populate_cache_leaves(unsigned int cpu)
 {
 	struct cpu_cacheinfo *this_cpu_ci = get_cpu_cacheinfo(cpu);
 	struct cacheinfo *this_leaf = this_cpu_ci->info_list;
-	struct device_node *np = of_cpu_device_node_get(cpu);
-	struct device_node *prev = NULL;
+	struct device_node *np, *prev;
 	int levels = 1, level = 1;
 
 	if (!acpi_disabled) {
@@ -105,6 +104,10 @@ int populate_cache_leaves(unsigned int cpu)
 		return 0;
 	}
 
+	np = of_cpu_device_node_get(cpu);
+	if (!np)
+		return -ENOENT;
+
 	if (of_property_read_bool(np, "cache-size"))
 		ci_leaf_init(this_leaf++, CACHE_TYPE_UNIFIED, level);
 	if (of_property_read_bool(np, "i-cache-size"))