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alpha: Allow HZ to be configured

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With the 1024Hz default, we spend 50% of QEMU emulation
processing timer interrupts.

Signed-off-by: Richard Henderson <rth@twiddle.net>
This commit is contained in:
Richard Henderson
2013-07-12 16:15:56 -07:00
committed by Matt Turner
parent 994dcf7055
commit fddd87d6e1
3 changed files with 59 additions and 11 deletions
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24
arch/alpha/kernel/time.c
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@@ -201,16 +201,26 @@ irqreturn_t timer_interrupt(int irq, void *dev)
void __init
common_init_rtc(void)
{
unsigned char x;
unsigned char x, sel = 0;
/* Reset periodic interrupt frequency. */
x = CMOS_READ(RTC_FREQ_SELECT) & 0x3f;
/* Test includes known working values on various platforms
where 0x26 is wrong; we refuse to change those. */
if (x != 0x26 && x != 0x25 && x != 0x19 && x != 0x06) {
printk("Setting RTC_FREQ to 1024 Hz (%x)\n", x);
CMOS_WRITE(0x26, RTC_FREQ_SELECT);
#if CONFIG_HZ == 1024 || CONFIG_HZ == 1200
x = CMOS_READ(RTC_FREQ_SELECT) & 0x3f;
/* Test includes known working values on various platforms
where 0x26 is wrong; we refuse to change those. */
if (x != 0x26 && x != 0x25 && x != 0x19 && x != 0x06) {
sel = RTC_REF_CLCK_32KHZ + 6;
}
#elif CONFIG_HZ == 256 || CONFIG_HZ == 128 || CONFIG_HZ == 64 || CONFIG_HZ == 32
sel = RTC_REF_CLCK_32KHZ + __builtin_ffs(32768 / CONFIG_HZ);
#else
# error "Unknown HZ from arch/alpha/Kconfig"
#endif
if (sel) {
printk(KERN_INFO "Setting RTC_FREQ to %d Hz (%x)\n",
CONFIG_HZ, sel);
CMOS_WRITE(sel, RTC_FREQ_SELECT);
}
/* Turn on periodic interrupts. */
x = CMOS_READ(RTC_CONTROL);