feat(allwinner): use reset through scpi for warm/soft reset

On systems with SCP (running crust) scpi_system_reboot action
performs board-level (PMIC) reboot. This doesn't preserve RAM content
on A64 PinePhone at least.

warm/soft system reset without RAM reset is required to get
pstore (persistent storage) in RAM working with Linux kernel. That is
very useful for oops/panic logging for post mortem analysis.

scpi_system_reset action performs reset via SoC reset (using watchdog)
and RAM content is preserved in this case. Linux kernel detects
system_reset2 support and uses it for warm reset automatically.

Change-Id: I1c21aa8f27c8e0395e2326034788693b59b80bc4
Signed-off-by: Andrey Skvortsov <andrej.skvortzov@gmail.com>

plat/allwinner/common/sunxi_scpi_pm.c

@@ -125,6 +125,32 @@ static void __dead2 sunxi_system_reset(void)
 	psci_power_down_wfi();
 }
 
+static int sunxi_system_reset2(int is_vendor, int reset_type, u_register_t cookie)
+{
+	uint32_t ret;
+
+	if (is_vendor || (reset_type != PSCI_RESET2_SYSTEM_WARM_RESET))
+		return PSCI_E_NOT_SUPPORTED;
+
+	gicv2_cpuif_disable();
+
+	/* Send the system reset request to the SCP. */
+	ret = scpi_sys_power_state(scpi_system_reset);
+	if (ret != SCP_OK) {
+		ERROR("PSCI: SCPI %s failed: %d\n", "reset", ret);
+		return PSCI_E_INVALID_PARAMS;
+	}
+
+	psci_power_down_wfi();
+
+	/*
+	 * Should not reach here.
+	 * However sunxi_system_reset2 has to return some value
+	 * according to PSCI v1.1 spec.
+	 */
+	return PSCI_E_SUCCESS;
+}
+
 static int sunxi_validate_power_state(unsigned int power_state,
 				      psci_power_state_t *req_state)
 {
@@ -177,6 +203,7 @@ static const plat_psci_ops_t sunxi_scpi_psci_ops = {
 	.pwr_domain_suspend_finish	= sunxi_pwr_domain_on_finish,
 	.system_off			= sunxi_system_off,
 	.system_reset			= sunxi_system_reset,
+	.system_reset2			= sunxi_system_reset2,
 	.validate_power_state		= sunxi_validate_power_state,
 	.validate_ns_entrypoint		= sunxi_validate_ns_entrypoint,
 	.get_sys_suspend_power_state	= sunxi_get_sys_suspend_power_state,