ARM: 8441/2: twd: Don't set CLOCK_EVT_FEAT_C3STOP unconditionally
In 5388a6b266 ("ARM: SMP: Always enable clock event broadcast support")
Russell noted that "the TWD local timers are unable to wake up the CPU
when it is placed into a low power mode".
However, some platforms do not stop the TWD block in low-power mode,
and can thus use the TWD timer in one-shot mode, without setting up
a broadcast device.
Make the driver check for the "always-on" boolean property, and set
the CLOCK_EVT_FEAT_C3STOP flag accordingly.
Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Marc Gonzalez <marc_gonzalez@sigmadesigns.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
diff --git a/Documentation/devicetree/bindings/arm/twd.txt b/Documentation/devicetree/bindings/arm/twd.txt
index 75b8610..383ea19 100644
--- a/Documentation/devicetree/bindings/arm/twd.txt
+++ b/Documentation/devicetree/bindings/arm/twd.txt
@@ -19,6 +19,11 @@
- reg : Specify the base address and the size of the TWD timer
register window.
+Optional
+
+- always-on : a boolean property. If present, the timer is powered through
+ an always-on power domain, therefore it never loses context.
+
Example:
twd-timer@2c000600 {
diff --git a/arch/arm/kernel/smp_twd.c b/arch/arm/kernel/smp_twd.c
index 662ed88..4c1aa61 100644
--- a/arch/arm/kernel/smp_twd.c
+++ b/arch/arm/kernel/smp_twd.c
@@ -33,6 +33,7 @@
static DEFINE_PER_CPU(bool, percpu_setup_called);
static struct clock_event_device __percpu *twd_evt;
+static int feat_c3stop;
static int twd_ppi;
static int twd_shutdown(struct clock_event_device *clk)
@@ -294,7 +295,7 @@
clk->name = "local_timer";
clk->features = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT |
- CLOCK_EVT_FEAT_C3STOP;
+ feat_c3stop;
clk->rating = 350;
clk->set_state_shutdown = twd_shutdown;
clk->set_state_periodic = twd_set_periodic;
@@ -349,6 +350,8 @@
goto out_irq;
twd_get_clock(np);
+ if (!of_property_read_bool(np, "always-on"))
+ feat_c3stop = CLOCK_EVT_FEAT_C3STOP;
/*
* Immediately configure the timer on the boot CPU, unless we need