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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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36
arch/alpha/Kconfig
View File

@ -627,9 +627,41 @@ config VERBOSE_MCHECK_ON
Take the default (1) unless you want more control or more info.
choice
prompt "Timer interrupt frequency (HZ)?"
default HZ_128 if ALPHA_QEMU
default HZ_1200 if ALPHA_RAWHIDE
default HZ_1024
---help---
The frequency at which timer interrupts occur. A high frequency
minimizes latency, whereas a low frequency minimizes overhead of
process accounting. The later effect is especially significant
when being run under QEMU.
Note that some Alpha hardware cannot change the interrupt frequency
of the timer. If unsure, say 1024 (or 1200 for Rawhide).
config HZ_32
bool "32 Hz"
config HZ_64
bool "64 Hz"
config HZ_128
bool "128 Hz"
config HZ_256
bool "256 Hz"
config HZ_1024
bool "1024 Hz"
config HZ_1200
bool "1200 Hz"
endchoice
config HZ
int
default 1200 if ALPHA_RAWHIDE
int
default 32 if HZ_32
default 64 if HZ_64
default 128 if HZ_128
default 256 if HZ_256
default 1200 if HZ_1200
default 1024
source "drivers/pci/Kconfig"

10
arch/alpha/kernel/setup.c
View File

@ -1218,6 +1218,7 @@ show_cpuinfo(struct seq_file *f, void *slot)
char *systype_name;
char *sysvariation_name;
int nr_processors;
unsigned long timer_freq;
cpu_index = (unsigned) (cpu->type - 1);
cpu_name = "Unknown";
@ -1229,6 +1230,12 @@ show_cpuinfo(struct seq_file *f, void *slot)
nr_processors = get_nr_processors(cpu, hwrpb->nr_processors);
#if CONFIG_HZ == 1024 || CONFIG_HZ == 1200
timer_freq = (100UL * hwrpb->intr_freq) / 4096;
#else
timer_freq = 100UL * CONFIG_HZ;
#endif
seq_printf(f, "cpu\t\t\t: Alpha\n"
"cpu model\t\t: %s\n"
"cpu variation\t\t: %ld\n"
@ -1254,8 +1261,7 @@ show_cpuinfo(struct seq_file *f, void *slot)
(char*)hwrpb->ssn,
est_cycle_freq ? : hwrpb->cycle_freq,
est_cycle_freq ? "est." : "",
hwrpb->intr_freq / 4096,
(100 * hwrpb->intr_freq / 4096) % 100,
timer_freq / 100, timer_freq % 100,
hwrpb->pagesize,
hwrpb->pa_bits,
hwrpb->max_asn,

24
arch/alpha/kernel/time.c
View File

@ -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);