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ARM: 8441/2: twd: Don't set CLOCK_EVT_FEAT_C3STOP unconditionally

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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>
This commit is contained in:
Marc Gonzalez 2015-10-09 10:20:47 +01:00 committed by Russell King
parent ff5138f3af
commit 194444c52e
2 changed files with 9 additions and 1 deletions
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5
Documentation/devicetree/bindings/arm/twd.txt
View File

@ -19,6 +19,11 @@ interrupts.
- 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 {

5
arch/arm/kernel/smp_twd.c
View File

@ -33,6 +33,7 @@ static unsigned long twd_timer_rate;
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 @@ static void twd_timer_setup(void)
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 @@ static int __init twd_local_timer_common_register(struct device_node *np)
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