On Tue, 2013-06-18 at 18:07 +0100, Sudeep KarkadaNagesha wrote:
> From: Sudeep KarkadaNagesha <[email protected]>
>
> Few control settings done in architected timer as part of initialisation
> are lost when CPU enters deeper power states. They need to be re-initialised
> when the CPU is (warm)reset again.
>
> This patch moves all such initialisation into separate function that can
> be used both in cold and warm CPU reset paths. It also adds CPU PM
> notifiers to do the timer initialisation on warm resets.
>
> Signed-off-by: Sudeep KarkadaNagesha <[email protected]>
> Reviewed-by: Lorenzo Pieralisi <[email protected]>
> Reviewed-by: Will Deacon <[email protected]>
> ---
> drivers/clocksource/arm_arch_timer.c | 51
> +++++++++++++++++++++++++++++++-----
> 1 file changed, 44 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/clocksource/arm_arch_timer.c
> b/drivers/clocksource/arm_arch_timer.c
> index 11aaf06..1c691b1 100644
> --- a/drivers/clocksource/arm_arch_timer.c
> +++ b/drivers/clocksource/arm_arch_timer.c
> @@ -13,6 +13,7 @@
> #include <linux/device.h>
> #include <linux/smp.h>
> #include <linux/cpu.h>
> +#include <linux/cpu_pm.h>
> #include <linux/clockchips.h>
> #include <linux/interrupt.h>
> #include <linux/of_irq.h>
> @@ -123,10 +124,20 @@ static int arch_timer_set_next_event_phys(unsigned long
> evt,
> return 0;
> }
>
> -static int __cpuinit arch_timer_setup(struct clock_event_device *clk)
> +static void arch_timer_initialise(void)
> {
> int evt_stream_div, pos;
>
> + /* Find the closest power of two to the divisor */
> + evt_stream_div = arch_timer_rate / ARCH_TIMER_EVT_STREAM_FREQ;
> + pos = fls(evt_stream_div);
> + if (pos > 1 && !(evt_stream_div & (1 << (pos - 2))))
> + pos--;
> + arch_counter_set_user_access(min(pos, 15));
Would it not be good to calculate the value once in arch_timer_setup
rather than repeatedly in this function? The calculations aren't that
expensive, but when I gave these patches a spin on TC2 I noticed that
this function gets called >500 times a second, so it seems a bit
wasteful.
> +}
> +
> +static int __cpuinit arch_timer_setup(struct clock_event_device *clk)
> +{
> clk->features = CLOCK_EVT_FEAT_ONESHOT | CLOCK_EVT_FEAT_C3STOP;
> clk->name = "arch_sys_timer";
> clk->rating = 450;
> @@ -155,12 +166,7 @@ static int __cpuinit arch_timer_setup(struct
> clock_event_device *clk)
> enable_percpu_irq(arch_timer_ppi[PHYS_NONSECURE_PPI],
> 0);
> }
>
> - /* Find the closest power of two to the divisor */
> - evt_stream_div = arch_timer_rate / ARCH_TIMER_EVT_STREAM_FREQ;
> - pos = fls(evt_stream_div);
> - if (pos > 1 && !(evt_stream_div & (1 << (pos - 2))))
> - pos--;
> - arch_counter_set_user_access(min(pos, 15));
> + arch_timer_initialise();
>
> return 0;
> }
> @@ -267,6 +273,31 @@ static struct notifier_block arch_timer_cpu_nb
> __cpuinitdata = {
> .notifier_call = arch_timer_cpu_notify,
> };
>
> +#ifdef CONFIG_CPU_PM
> +static int arch_timer_cpu_pm_notify(struct notifier_block *self,
> + unsigned long action, void *hcpu)
> +{
> + if (action == CPU_PM_EXIT)
> + arch_timer_initialise();
> +
> + return NOTIFY_OK;
> +}
> +
> +static struct notifier_block arch_timer_cpu_pm_notifier = {
> + .notifier_call = arch_timer_cpu_pm_notify,
> +};
> +
> +static int __init arch_timer_cpu_pm_init(void)
> +{
> + return cpu_pm_register_notifier(&arch_timer_cpu_pm_notifier);
> +}
> +#else
> +static int __init arch_timer_cpu_pm_init(void)
> +{
> + return 0;
> +}
> +#endif
> +
> static int __init arch_timer_register(void)
> {
> int err;
> @@ -316,11 +347,17 @@ static int __init arch_timer_register(void)
> if (err)
> goto out_free_irq;
>
> + err = arch_timer_cpu_pm_init();
> + if (err)
> + goto out_unreg_notify;
> +
> /* Immediately configure the timer on the boot CPU */
> arch_timer_setup(this_cpu_ptr(arch_timer_evt));
>
> return 0;
>
> +out_unreg_notify:
> + unregister_cpu_notifier(&arch_timer_cpu_nb);
> out_free_irq:
> if (arch_timer_use_virtual)
> free_percpu_irq(arch_timer_ppi[VIRT_PPI], arch_timer_evt);
--
Tixy
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
