From mboxrd@z Thu Jan 1 00:00:00 1970 From: mark.rutland@arm.com (Mark Rutland) Date: Thu, 8 Oct 2015 18:16:16 +0100 Subject: [PATCH v4] twd: Don't set CLOCK_EVT_FEAT_C3STOP unconditionally In-Reply-To: <5612649C.5020401@sigmadesigns.com> References: <56123BD0.8010005@sigmadesigns.com> <56124035.6080107@sigmadesigns.com> <561247DF.1000308@sigmadesigns.com> <20151005103539.GC19064@leverpostej> <5612649C.5020401@sigmadesigns.com> Message-ID: <20151008171616.GG7275@leverpostej> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Mon, Oct 05, 2015 at 01:53:00PM +0200, Marc Gonzalez wrote: > 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 "twd-never-stops" boolean property, > and set the CLOCK_EVT_FEAT_C3STOP flag accordingly. > > Signed-off-by: Marc Gonzalez > --- > Documentation/devicetree/bindings/arm/twd.txt | 4 ++++ > arch/arm/kernel/smp_twd.c | 5 ++++- > 2 files changed, 8 insertions(+), 1 deletion(-) > > diff --git a/Documentation/devicetree/bindings/arm/twd.txt b/Documentation/devicetree/bindings/arm/twd.txt > index 75b8610939fa..700a517b000e 100644 > --- a/Documentation/devicetree/bindings/arm/twd.txt > +++ b/Documentation/devicetree/bindings/arm/twd.txt > @@ -19,6 +19,10 @@ interrupts. > - reg : Specify the base address and the size of the TWD timer > register window. > > +Optional > +- twd-never-stops : boolean property. If present, TWD timers are expected > + to keep generating interrupts, even when the CPU is in low-power mode. Sorry for the last minute bikeshed, but it would be better if we could align this with the ARM generic timer binding, both in naming and description: - always-on : a boolean property. If present, the timer is powered through an always-on power domain, therefore it never loses context. Otherwise this looks ok. If you can respin with the above wording, and s/twd-never-stops/always-on/ in the patch, you can add: Acked-by: Mark Rutland Thanks, Mark. > + > Example: > > twd-timer at 2c000600 { > diff --git a/arch/arm/kernel/smp_twd.c b/arch/arm/kernel/smp_twd.c > index e8f6d241881f..79298d4fb41f 100644 > --- a/arch/arm/kernel/smp_twd.c > +++ b/arch/arm/kernel/smp_twd.c > @@ -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 void twd_set_mode(enum clock_event_mode mode, > @@ -293,7 +294,7 @@ 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_mode = twd_set_mode; > clk->set_next_event = twd_set_next_event; > @@ -345,6 +346,8 @@ 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, "twd-never-stops")) > + feat_c3stop = CLOCK_EVT_FEAT_C3STOP; > > /* > * Immediately configure the timer on the boot CPU, unless we need > -- > 2.4.5 >