shinys000114/linux
1
0
Fork 0
mirror of https://github.com/hardkernel/linux.git synced 2026-06-10 21:07:02 +09:00
Code Issues Packages Projects Releases Wiki Activity

ARM: smp_twd: Avoid recalibrating local timer

Browse Source 
Change-Id: I10af3139ecd0dc1ef54e7a8e5258ee6fb29bfb0c
Signed-off-by: Colin Cross <ccross@android.com>
This commit is contained in:
Colin Cross
2010-12-29 19:51:35 -08:00
parent 85d90d7d61
commit e5603f1350
1 changed files with 45 additions and 32 deletions
Download Patch File Download Diff File Expand all files Collapse all files

77
arch/arm/kernel/smp_twd.c
View File

@@ -26,7 +26,7 @@ void __iomem *twd_base;
static unsigned long twd_timer_rate;
static unsigned long twd_periphclk_prescaler;
static unsigned long twd_target_rate;
static unsigned long twd_cpu_rate;
static void twd_set_mode(enum clock_event_mode mode,
struct clock_event_device *clk)
@@ -82,6 +82,12 @@ int twd_timer_ack(void)
return 0;
}
/*
* Recalculate the twd prescaler value when the cpu frequency changes. To
* prevent early timer interrupts, must be called before changing the cpu
* frequency if the frequency is increasing, or after if the frequency is
* decreasing.
*/
void twd_recalc_prescaler(unsigned long new_rate)
{
u32 ctrl;
@@ -90,6 +96,8 @@ void twd_recalc_prescaler(unsigned long new_rate)
BUG_ON(twd_periphclk_prescaler == 0 || twd_timer_rate == 0);
twd_cpu_rate = new_rate;
periphclk_rate = new_rate / twd_periphclk_prescaler;
prescaler = DIV_ROUND_UP(periphclk_rate, twd_timer_rate);
@@ -106,55 +114,60 @@ static void __cpuinit twd_calibrate_rate(unsigned long target_rate,
{
unsigned long load, count;
u64 waitjiffies;
unsigned long cpu_rate;
/*
* If this is the first time round, we need to work out how fast
* the timer ticks
*/
printk(KERN_INFO "Calibrating local timer... ");
if (twd_timer_rate == 0) {
printk(KERN_INFO "Calibrating local timer... ");
/* Wait for a tick to start */
waitjiffies = get_jiffies_64() + 1;
/* Wait for a tick to start */
waitjiffies = get_jiffies_64() + 1;
while (get_jiffies_64() < waitjiffies)
udelay(10);
while (get_jiffies_64() < waitjiffies)
udelay(10);
/* OK, now the tick has started, let's get the timer going */
waitjiffies += 5;
/* OK, now the tick has started, let's get the timer going */
waitjiffies += 5;
/* enable, no interrupt or reload */
__raw_writel(0x1, twd_base + TWD_TIMER_CONTROL);
/* enable, no interrupt or reload */
__raw_writel(0x1, twd_base + TWD_TIMER_CONTROL);
/* maximum value */
__raw_writel(0xFFFFFFFFU, twd_base + TWD_TIMER_COUNTER);
/* maximum value */
__raw_writel(0xFFFFFFFFU, twd_base + TWD_TIMER_COUNTER);
while (get_jiffies_64() < waitjiffies)
udelay(10);
while (get_jiffies_64() < waitjiffies)
udelay(10);
count = __raw_readl(twd_base + TWD_TIMER_COUNTER);
count = __raw_readl(twd_base + TWD_TIMER_COUNTER);
twd_timer_rate = (0xFFFFFFFFU - count) * (HZ / 5);
twd_timer_rate = (0xFFFFFFFFU - count) * (HZ / 5);
/*
* If a target rate has been requested, adjust the TWD prescaler
* to get the closest lower frequency.
*/
if (target_rate) {
twd_periphclk_prescaler = periphclk_prescaler;
twd_target_rate = target_rate;
/*
* If a target rate has been requested, adjust the TWD prescaler
* to get the closest lower frequency.
*/
if (target_rate) {
twd_periphclk_prescaler = periphclk_prescaler;
printk("%lu.%02luMHz, setting to ",
twd_timer_rate / 1000000,
printk("%lu.%02luMHz, setting to ",
twd_timer_rate / 1000000,
(twd_timer_rate / 10000) % 100);
twd_cpu_rate = twd_timer_rate * periphclk_prescaler;
twd_timer_rate = target_rate;
twd_recalc_prescaler(twd_cpu_rate);
}
printk("%lu.%02luMHz.\n", twd_timer_rate / 1000000,
(twd_timer_rate / 10000) % 100);
cpu_rate = twd_timer_rate * periphclk_prescaler;
twd_timer_rate = twd_target_rate;
twd_recalc_prescaler(cpu_rate);
} else {
if (target_rate) {
BUG_ON(target_rate != twd_timer_rate);
twd_recalc_prescaler(twd_cpu_rate);
}
}
printk("%lu.%02luMHz.\n", twd_timer_rate / 1000000,
(twd_timer_rate / 10000) % 100);
load = twd_timer_rate / HZ;
__raw_writel(load, twd_base + TWD_TIMER_LOAD);