firmware: psci: Export functions to manage the OSI mode

To allow subsequent changes to implement support for OSI mode through the
cpuidle-psci driver, export the existing psci_has_osi_support(). Export
also a new function, psci_set_osi_mode(), that allows its caller to enable
the OS-initiated CPU-suspend mode in the PSCI FW.

To deal with backwards compatibility for a kernel started through a kexec
call, default to set the CPU-suspend mode to the Platform Coordinated mode
during boot.
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Reviewed-by: Sudeep Holla <sudeep.holla@arm.com>

drivers/firmware/psci/psci.c

@@ -97,7 +97,7 @@ static inline bool psci_has_ext_power_state(void)
 				PSCI_1_0_FEATURES_CPU_SUSPEND_PF_MASK;
 }
 
-static inline bool psci_has_osi_support(void)
+bool psci_has_osi_support(void)
 {
 	return psci_cpu_suspend_feature & PSCI_1_0_OS_INITIATED;
 }
@@ -162,6 +162,15 @@ static u32 psci_get_version(void)
 	return invoke_psci_fn(PSCI_0_2_FN_PSCI_VERSION, 0, 0, 0);
 }
 
+int psci_set_osi_mode(void)
+{
+	int err;
+
+	err = invoke_psci_fn(PSCI_1_0_FN_SET_SUSPEND_MODE,
+			     PSCI_1_0_SUSPEND_MODE_OSI, 0, 0);
+	return psci_to_linux_errno(err);
+}
+
 static int psci_cpu_suspend(u32 state, unsigned long entry_point)
 {
 	int err;
@@ -544,9 +553,14 @@ static int __init psci_1_0_init(struct device_node *np)
 	if (err)
 		return err;
 
-	if (psci_has_osi_support())
+	if (psci_has_osi_support()) {
 		pr_info("OSI mode supported.\n");
 
+		/* Default to PC mode. */
+		invoke_psci_fn(PSCI_1_0_FN_SET_SUSPEND_MODE,
+			       PSCI_1_0_SUSPEND_MODE_PC, 0, 0);
+	}
+
 	return 0;
 }
 

include/linux/psci.h

@@ -18,6 +18,8 @@ bool psci_tos_resident_on(int cpu);
 
 int psci_cpu_suspend_enter(u32 state);
 bool psci_power_state_is_valid(u32 state);
+int psci_set_osi_mode(void);
+bool psci_has_osi_support(void);
 
 enum smccc_version {
 	SMCCC_VERSION_1_0,