Tegra: PM: soc-specific system off handler

This patch introduces a power down handler which can be overriden
by SoCs to customise the power down process. The current SoCs do
not have a way of powering down the entire system as external PMIC
chips are involved in the process.

But future SoCs will have a way to power off the entire system
without talking to an external PMIC.

Change-Id: Ie7750714141a29cb0a1a616fafc531c4f11d0985
Signed-off-by: Varun Wadekar <vwadekar@nvidia.com>

plat/nvidia/tegra/common/tegra_pm.c

@@ -55,6 +55,7 @@ extern uint64_t tegra_sec_entry_point;
 #pragma weak tegra_soc_pwr_domain_off
 #pragma weak tegra_soc_pwr_domain_on_finish
 #pragma weak tegra_soc_prepare_system_reset
+#pragma weak tegra_soc_prepare_system_off
 
 int tegra_soc_pwr_domain_suspend(const psci_power_state_t *target_state)
 {
@@ -81,6 +82,12 @@ int tegra_soc_prepare_system_reset(void)
 	return PSCI_E_SUCCESS;
 }
 
+__dead2 void tegra_soc_prepare_system_off(void)
+{
+	ERROR("Tegra System Off: operation not handled.\n");
+	panic();
+}
+
 /*******************************************************************************
  * This handler is called by the PSCI implementation during the `SYSTEM_SUSPEND`
  * call to get the `power_state` parameter. This allows the platform to encode
@@ -199,8 +206,9 @@ void tegra_pwr_domain_suspend_finish(const psci_power_state_t *target_state)
  ******************************************************************************/
 __dead2 void tegra_system_off(void)
 {
-	ERROR("Tegra System Off: operation not handled.\n");
-	panic();
+	INFO("Powering down system...\n");
+
+	tegra_soc_prepare_system_off();
 }
 
 /*******************************************************************************
@@ -208,6 +216,8 @@ __dead2 void tegra_system_off(void)
  ******************************************************************************/
 __dead2 void tegra_system_reset(void)
 {
+	INFO("Restarting system...\n");
+
 	/* per-SoC system reset handler */
 	tegra_soc_prepare_system_reset();