Tegra210: toggle ring oscillator across cluster idle

This patch toggles the ring oscillator state across cluster idle
as DFLL loses its state. We dont want garbage values being written
to the pmic when we enter cluster idle state, so enable "open loop"
when we enter CC6 and restore the state to "closed loop" on exit.

Change-Id: I56f4649f57bcc651d6c415a6dcdc978e9444c97b
Signed-off-by: Varun Wadekar <vwadekar@nvidia.com>

plat/nvidia/tegra/soc/t210/plat_psci_handlers.c

@@ -119,6 +119,13 @@ plat_local_state_t tegra_soc_get_target_pwr_state(unsigned int lvl,
 		ret = tegra_bpmp_init();
 		if (ret != 0U) {
 
+			/*
+			 * flag to indicate that BPMP firmware is not
+			 * available and the CPU has to handle entry/exit
+			 * for all power states
+			 */
+			tegra_bpmp_available = false;
+
 			/* Cluster idle not allowed */
 			target = PSCI_LOCAL_STATE_RUN;
 
@@ -130,13 +137,6 @@ plat_local_state_t tegra_soc_get_target_pwr_state(unsigned int lvl,
 			/* check if cluster idle state has been enabled */
 			val = mmio_read_32(TEGRA_CL_DVFS_BASE + DVFS_DFLL_CTRL);
 			if (val == ENABLE_CLOSED_LOOP) {
-				/*
-				 * flag to indicate that BPMP firmware is not
-				 * available and the CPU has to handle entry/exit
-				 * for all power states
-				 */
-				tegra_bpmp_available = false;
-
 				/*
 				 * Acquire the cluster idle lock to stop
 				 * other CPUs from powering up.
@@ -217,6 +217,15 @@ int tegra_soc_pwr_domain_suspend(const psci_power_state_t *target_state)
 
 		if (!tegra_bpmp_available) {
 
+			/*
+			 * When disabled, DFLL loses its state. Enable
+			 * open loop state for the DFLL as we dont want
+			 * garbage values being written to the pmic
+			 * when we enter cluster idle state.
+			 */
+			mmio_write_32(TEGRA_CL_DVFS_BASE + DVFS_DFLL_CTRL,
+				      ENABLE_OPEN_LOOP);
+
 			/* Find if the platform uses OVR2/MAX77621 PMIC */
 			cfg = mmio_read_32(TEGRA_CL_DVFS_BASE + DVFS_DFLL_OUTPUT_CFG);
 			if (cfg & DFLL_OUTPUT_CFG_CLK_EN_BIT) {
@@ -481,8 +490,19 @@ int tegra_soc_pwr_domain_on_finish(const psci_power_state_t *target_state)
 				val = mmio_read_32(TEGRA_MISC_BASE + PINMUX_AUX_DVFS_PWM);
 				val &= ~PINMUX_PWM_TRISTATE;
 				mmio_write_32(TEGRA_MISC_BASE + PINMUX_AUX_DVFS_PWM, val);
+
+				/* make sure the setting took effect */
+				val = mmio_read_32(TEGRA_MISC_BASE + PINMUX_AUX_DVFS_PWM);
+				assert((val & PINMUX_PWM_TRISTATE) == 0U);
 			}
 
+			/*
+			 * Restore operation mode for the DFLL ring
+			 * oscillator
+			 */
+			mmio_write_32(TEGRA_CL_DVFS_BASE + DVFS_DFLL_CTRL,
+				      ENABLE_CLOSED_LOOP);
+
 			/* release cluster idle lock */
 			tegra_fc_ccplex_pgexit_unlock();
 		}