Commit fddd87d6 authored by Richard Henderson's avatar Richard Henderson Committed by Matt Turner
Browse files

alpha: Allow HZ to be configured 



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

Signed-off-by: default avatarRichard Henderson <rth@twiddle.net>
parent 994dcf70

arch/alpha/Kconfig

+34 −2
Original line number Diff line number Diff line
@@ -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

	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"

arch/alpha/kernel/setup.c

+8 −2
Original line number Diff line number Diff line
@@ -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,

arch/alpha/kernel/time.c

+17 −7
Original line number Diff line number Diff line
@@ -201,15 +201,25 @@ 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.  */

#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) {

		printk("Setting RTC_FREQ to 1024 Hz (%x)\n", x);

		CMOS_WRITE(0x26, RTC_FREQ_SELECT);

		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.  */