Turned out that WFI doesn't work reliably on Tegra30 as a trigger for
the power-gating, it causes CPU hang under some circumstances like having
memory controller running of PLLP. The TRM doc states that WFI should be
used for the Big-Little "Cluster Switch", while WFE for the power-gating.
Hence let's use the WFE for CPU0 power-gating, like it is done for the
power-gating of a secondary cores. This fixes CPU hang after entering LP2
with memory running off PLLP.
Signed-off-by: Dmitry Osipenko <digetx@xxxxxxxxx>
---
arch/arm/mach-tegra/sleep-tegra30.S | 4 +++-
drivers/soc/tegra/flowctrl.c | 19 +++++++++++++++++--
2 files changed, 20 insertions(+), 3 deletions(-)
diff --git a/arch/arm/mach-tegra/sleep-tegra30.S b/arch/arm/mach-tegra/sleep-tegra30.S
index e95e46d65e8c..2e42f2bc0630 100644
--- a/arch/arm/mach-tegra/sleep-tegra30.S
+++ b/arch/arm/mach-tegra/sleep-tegra30.S
@@ -683,10 +683,12 @@ tegra30_enter_sleep:
dsb
ldr r0, [r6, r2] /* memory barrier */
+ cmp r10, #TEGRA30
halted:
isb
dsb
- wfi /* CPU should be power gated here */
+ wfine /* CPU should be power gated here */
+ wfeeq
/* !!!FIXME!!! Implement halt failure handler */
b halted
diff --git a/drivers/soc/tegra/flowctrl.c b/drivers/soc/tegra/flowctrl.c
index b6bdeef33db1..b62ff4c1b997 100644
--- a/drivers/soc/tegra/flowctrl.c
+++ b/drivers/soc/tegra/flowctrl.c
@@ -91,8 +91,23 @@ void flowctrl_cpu_suspend_enter(unsigned int cpuid)
reg &= ~TEGRA30_FLOW_CTRL_CSR_WFE_BITMAP;
/* clear wfi bitmap */
reg &= ~TEGRA30_FLOW_CTRL_CSR_WFI_BITMAP;
- /* pwr gating on wfi */
- reg |= TEGRA30_FLOW_CTRL_CSR_WFI_CPU0 << cpuid;
+
+ if (tegra_get_chip_id() == TEGRA30) {
+ /*
+ * The wfi doesn't work well on Tegra30 because
+ * CPU hangs under some odd circumstances after
+ * power-gating (like memory running off PLLP),
+ * hence use wfe that is working perfectly well.
+ * Note that Tegra30 TRM doc clearly stands that
+ * wfi should be used for "Cluster Switching",
+ * while wfe for the power-gating just like it is
+ * done on Tegra20.
+ */
+ reg |= TEGRA20_FLOW_CTRL_CSR_WFE_CPU0 << cpuid;
+ } else {
+ /* pwr gating on wfi */
+ reg |= TEGRA30_FLOW_CTRL_CSR_WFI_CPU0 << cpuid;
+ }
break;
}
reg |= FLOW_CTRL_CSR_INTR_FLAG; /* clear intr flag */
--
2.22.0
