[PATCH v6 10/18] arm: tegra20: cpuidle: Handle case where secondary CPU hangs on entering LP2

[Dmitry Osipenko <digetx@gmail.com>]

It is possible that something may go wrong with the secondary CPU, in that
case it is much nicer to get a dump of the flow-controller state before
hanging machine.

Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
---
 arch/arm/mach-tegra/cpuidle-tegra20.c | 46 +++++++++++++++++++++++++--
 1 file changed, 44 insertions(+), 2 deletions(-)

diff --git a/arch/arm/mach-tegra/cpuidle-tegra20.c b/arch/arm/mach-tegra/cpuidle-tegra20.c
index 77702dd42479..bc5873e92af5 100644
--- a/arch/arm/mach-tegra/cpuidle-tegra20.c
+++ b/arch/arm/mach-tegra/cpuidle-tegra20.c
@@ -83,14 +83,56 @@ static inline void tegra20_wake_cpu1_from_reset(void)
 }
 #endif
 
+static void tegra20_report_cpus_state(void)
+{
+	unsigned int cpu, lcpu;
+
+	pr_err("secondary CPU taking too long to park\n");
+
+	for_each_cpu(lcpu, cpu_possible_mask) {
+		cpu = cpu_logical_map(lcpu);
+
+		pr_err("cpu%u: online=%d flowctrl_csr=0x%08x\n",
+		       cpu, cpu_online(lcpu), flowctrl_read_cpu_csr(cpu));
+	}
+}
+
+static int tegra20_wait_for_secondary_cpu_parking(void)
+{
+	unsigned int retries = 3;
+
+	while (retries--) {
+		ktime_t timeout = ktime_add_ms(ktime_get(), 500);
+
+		/*
+		 * The primary CPU0 core shall wait for the secondaries
+		 * shutdown in order to power-off CPU's cluster safely.
+		 * The timeout value depends on the current CPU frequency,
+		 * it takes about 40-150us  in average and over 1000us in
+		 * a worst case scenario.
+		 */
+		do {
+			if (tegra_cpu_rail_off_ready())
+				return 0;
+
+		} while (ktime_before(ktime_get(), timeout));
+
+		tegra20_report_cpus_state();
+	}
+
+	pr_err("timed out waiting secondaries to park\n");
+
+	return -ETIMEDOUT;
+}
+
 static bool tegra20_cpu_cluster_power_down(struct cpuidle_device *dev,
 					   struct cpuidle_driver *drv,
 					   int index)
 {
 	bool ret;
 
-	while (!tegra_cpu_rail_off_ready())
-		cpu_relax();
+	if (tegra20_wait_for_secondary_cpu_parking())
+		return false;
 
 	ret = !tegra_pm_enter_lp2();
 
-- 
2.23.0