firmware: psci: Set pm_set_resume/suspend_via_firmware() for SYSTEM_SUSPEND

PSCI specification defines the SYSTEM_SUSPEND feature which enables the
firmware to implement the suspend to RAM (S2RAM) functionality by
transitioning the system to a deeper low power state. When the system
enters such state, the power to the peripheral devices might be removed. So
the respective device drivers must prepare for the possible removal of the
power by performing actions such as shutting down or resetting the device
in their system suspend callbacks.

The Linux PM framework allows the platform drivers to convey this info to
device drivers by calling the pm_set_suspend_via_firmware() and
pm_set_resume_via_firmware() APIs.

Hence, if the PSCI firmware supports SYSTEM_SUSPEND feature, call the above
mentioned APIs in the psci_system_suspend_begin() and
psci_system_suspend_enter() callbacks.

Signed-off-by: Konrad Dybcio <konrad.dybcio@linaro.org>
Reviewed-by: Sudeep Holla <sudeep.holla@arm.com>
[mani: reworded the description to be more elaborative]
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@oss.qualcomm.com>
Tested-by: Jon Hunter <jonathanh@nvidia.com>
Acked-by: Jon Hunter <jonathanh@nvidia.com>
Acked-by: Lorenzo Pieralisi <lpieralisi@kernel.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

Author: konradybcio

drivers/firmware/psci/psci.c

@@ -539,12 +539,22 @@ static int psci_system_suspend(unsigned long unused)
 
 static int psci_system_suspend_enter(suspend_state_t state)
 {
+	pm_set_resume_via_firmware();
+
 	return cpu_suspend(0, psci_system_suspend);
 }
 
+static int psci_system_suspend_begin(suspend_state_t state)
+{
+	pm_set_suspend_via_firmware();
+
+	return 0;
+}
+
 static const struct platform_suspend_ops psci_suspend_ops = {
 	.valid          = suspend_valid_only_mem,
 	.enter          = psci_system_suspend_enter,
+	.begin          = psci_system_suspend_begin,
 };
 
 static void __init psci_init_system_reset2(void)