From: slash.tmp@free•fr (Mason)
To: linux-arm-kernel@lists•infradead.org
Subject: schedule_timeout sleeps too long after dividing CPU frequency
Date: Thu, 21 May 2015 14:35:42 +0200 [thread overview]
Message-ID: <555DD11E.7080302@free.fr> (raw)
In-Reply-To: <2681862.SyQNaSxams@wuerfel>
On 21/05/2015 00:18, Arnd Bergmann wrote:
> On Wednesday 20 May 2015 23:56:31 Mason wrote:
>
>> Or perhaps the other way around?
>> i.e. feat_c3stop initialized to 0 (thus in the bss section)
>> and set to FEAT_C3STOP if "twd_never_stops" doesn't exist...
>
> yes.
IIUC, something along these lines:
diff --git a/arch/arm/kernel/smp_twd.c b/arch/arm/kernel/smp_twd.c
index 172c6a05..e10a388 100644
--- a/arch/arm/kernel/smp_twd.c
+++ b/arch/arm/kernel/smp_twd.c
@@ -34,6 +34,7 @@ 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,
@@ -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_mode = twd_set_mode;
clk->set_next_event = twd_set_next_event;
@@ -346,6 +347,8 @@ 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
>> Russell, when you added the FEAT_C3STOP flag unconditionally in
>> commit 5388a6b266, didn't that potentially break platforms that
>> didn't expect the flag to be set?
>
> To take a step back, you should first figure out whether clearing
> this flag is actually the correct behavior for your hardware, or
> just happens to work by accident.
According to my (limited) understanding of the clockevents core,
a "broadcast device" is required if and only if the local timers
have CLOCK_EVT_FEAT_C3STOP. I could be wrong.
Additional reference:
https://lwn.net/Articles/574962/
Regards.
next prev parent reply other threads:[~2015-05-21 12:35 UTC|newest]
Thread overview: 46+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-05-12 14:32 schedule_timeout sleeps too long after dividing CPU frequency Mason
2015-05-12 14:46 ` Viresh Kumar
2015-05-12 15:14 ` Mason
2015-05-12 15:50 ` Russell King - ARM Linux
2015-05-12 16:14 ` Mason
2015-05-13 16:51 ` Mason
2015-05-14 2:13 ` Viresh Kumar
2015-05-14 11:22 ` Mason
2015-05-14 11:54 ` Viresh Kumar
2015-05-14 13:06 ` Mason
2015-05-14 13:53 ` Russell King - ARM Linux
2015-05-14 14:51 ` Mason
2015-05-14 13:59 ` Viresh Kumar
2015-05-14 14:38 ` Viresh Kumar
2015-05-14 14:42 ` Russell King - ARM Linux
2015-05-15 9:29 ` Mason
2015-05-15 9:51 ` Russell King - ARM Linux
2015-05-15 10:01 ` Viresh Kumar
2015-05-15 10:36 ` Mason
2015-05-15 11:58 ` Russell King - ARM Linux
2015-05-15 12:45 ` Mason
2015-05-15 13:15 ` Russell King - ARM Linux
2015-05-15 13:58 ` Mason
2015-05-15 18:35 ` Mason
2015-05-18 11:24 ` Mason
2015-05-18 11:54 ` Russell King - ARM Linux
2015-05-20 16:21 ` Mason
2015-05-20 18:50 ` Arnd Bergmann
2015-05-20 19:34 ` Mason
2015-05-20 20:14 ` Russell King - ARM Linux
2015-05-20 20:41 ` Mason
2015-05-20 20:52 ` Arnd Bergmann
2015-05-20 21:56 ` Mason
2015-05-20 22:18 ` Arnd Bergmann
2015-05-21 12:35 ` Mason [this message]
2015-05-20 23:14 ` Russell King - ARM Linux
2015-05-21 9:56 ` Mason
2015-05-21 10:20 ` Russell King - ARM Linux
2015-05-14 14:48 ` Mason
2015-05-15 4:16 ` Viresh Kumar
2015-05-15 5:07 ` Viresh Kumar
2015-05-15 9:00 ` Russell King - ARM Linux
2015-05-15 9:21 ` Mason
2015-05-15 10:11 ` Mason
2015-05-12 15:23 ` Russell King - ARM Linux
2015-05-12 16:03 ` Mason
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