diff options
| author | Martin Persson <martin.persson@stericsson.com> | 2010-12-21 08:30:18 +0100 |
|---|---|---|
| committer | Ulf Hansson <ulf.hansson@stericsson.com> | 2011-09-19 15:14:34 +0200 |
| commit | 433955b4c2b9ce6ff3d2459d9e4c87b913ab4583 (patch) | |
| tree | e86d5250d78800c34b7ee1e25340cb697c4b5526 /arch/arm/include/asm | |
| parent | 02b40de1867fb2b6bdbc6004b8cfcae7310a6ce0 (diff) | |
ARM: twd: Adjust localtimer frequency with cpufreq notifiers
The clock to the ARM TWD local timer scales with the cpu
frequency. To allow the cpu frequency to change while
maintaining a constant TWD frequency, pick a lower target
frequency for the TWD and use the prescaler to divide down
to the closest lower frequency.
This patch provides a new initialization function that takes
a target TWD frequency and the ratio between the cpu
clock and the TWD clock, specified as an integer divider >= 2
in the Cortex A9 MPCore TRM, and 2 in the ARM11 MPCore TRM.
It also registers a cpufreq notifier that adjusts the
prescaler when the cpu frequency changes.
ST-Ericsson Linux next: Colin is driving this
ST-Ericsson ID: 279802
ST-Ericsson FOSS-OUT ID: Trivial
Change-Id: Ieec17963da8d7d37d935782633406bc1a0484dc9
Signed-off-by: Colin Cross <ccross@android.com>
Reviewed-on: http://gerrit.lud.stericsson.com/gerrit/11532
Tested-by: Martin PERSSON <martin.persson@stericsson.com>
Reviewed-by: QATOOLS
Reviewed-by: Jonas ABERG <jonas.aberg@stericsson.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Diffstat (limited to 'arch/arm/include/asm')
| -rw-r--r-- | arch/arm/include/asm/smp_twd.h | 11 |
1 files changed, 11 insertions, 0 deletions
diff --git a/arch/arm/include/asm/smp_twd.h b/arch/arm/include/asm/smp_twd.h index fed9981fba0..859be20c38b 100644 --- a/arch/arm/include/asm/smp_twd.h +++ b/arch/arm/include/asm/smp_twd.h @@ -17,6 +17,7 @@ #define TWD_TIMER_CONTROL_ONESHOT (0 << 1) #define TWD_TIMER_CONTROL_PERIODIC (1 << 1) #define TWD_TIMER_CONTROL_IT_ENABLE (1 << 2) +#define TWD_TIMER_CONTROL_PRESCALE_MASK (0xFF << 8) struct clock_event_device; @@ -25,4 +26,14 @@ extern void __iomem *twd_base; int twd_timer_ack(void); void twd_timer_setup(struct clock_event_device *); +/* + * Use this setup function on systems that support cpufreq. + * periphclk_prescaler is the fixed divider value between the cpu + * clock and the PERIPHCLK clock that feeds the TWD. target_rate should be + * low enough that the prescaler can accurately reach the target rate from the + * lowest cpu frequency, but high enough to give a reasonable timer accuracy. + */ +void twd_timer_setup_scalable(struct clock_event_device *, + unsigned long target_rate, unsigned int periphclk_prescaler); + #endif |