psci: Support psci_ops.get_version for v0.1

KVM's host PSCI SMC filter needs to be aware of the PSCI version of the
system but currently it is impossible to distinguish between v0.1 and
PSCI disabled because both have get_version == NULL.

Populate get_version for v0.1 with a function that returns a constant.

psci_opt.get_version is currently unused so this has no effect on
existing functionality.
Signed-off-by: David Brazdil <dbrazdil@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Link: https://lore.kernel.org/r/20201202184122.26046-4-dbrazdil@google.com

drivers/firmware/psci/psci.c

@@ -146,7 +146,12 @@ static int psci_to_linux_errno(int errno)
 	return -EINVAL;
 }
 
-static u32 psci_get_version(void)
+static u32 psci_0_1_get_version(void)
+{
+	return PSCI_VERSION(0, 1);
+}
+
+static u32 psci_0_2_get_version(void)
 {
 	return invoke_psci_fn(PSCI_0_2_FN_PSCI_VERSION, 0, 0, 0);
 }
@@ -421,7 +426,7 @@ static void __init psci_init_smccc(void)
 static void __init psci_0_2_set_functions(void)
 {
 	pr_info("Using standard PSCI v0.2 function IDs\n");
-	psci_ops.get_version = psci_get_version;
+	psci_ops.get_version = psci_0_2_get_version;
 
 	psci_function_id[PSCI_FN_CPU_SUSPEND] =
 					PSCI_FN_NATIVE(0_2, CPU_SUSPEND);
@@ -450,7 +455,7 @@ static void __init psci_0_2_set_functions(void)
  */
 static int __init psci_probe(void)
 {
-	u32 ver = psci_get_version();
+	u32 ver = psci_0_2_get_version();
 
 	pr_info("PSCIv%d.%d detected in firmware.\n",
 			PSCI_VERSION_MAJOR(ver),
@@ -514,6 +519,8 @@ static int __init psci_0_1_init(struct device_node *np)
 
 	pr_info("Using PSCI v0.1 Function IDs from DT\n");
 
+	psci_ops.get_version = psci_0_1_get_version;
+
 	if (!of_property_read_u32(np, "cpu_suspend", &id)) {
 		psci_function_id[PSCI_FN_CPU_SUSPEND] = id;
 		psci_ops.cpu_suspend = psci_cpu_suspend;