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cpufreq: pmac64: speed up frequency switch 

Some functions on switch path use msleep() which is inaccurate, and
depends on HZ. With HZ=100 msleep(1) takes actually over ten times longer.
Using usleep_range() we get more accurate sleeps.

I measured the "pfunc_slewing_done" polling to take 300us at max (on
2.3GHz dual-processor Xserve G5), so using 500us sleep there should
be fine.

With the patch, g5_switch_freq() duration drops from ~50ms to ~10ms on
Xserve with HZ=100.

Signed-off-by: Aaro Koskinen <aaro.koskinen@iki.fi>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
This commit is contained in:
Aaro Koskinen 2013-09-30 23:44:31 +03:00 committed by Rafael J. Wysocki
parent fbbc5bfb44
commit 45a428ebbf
1 changed files with 3 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

6
drivers/cpufreq/pmac64-cpufreq.c
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@ -137,7 +137,7 @@ static void g5_vdnap_switch_volt(int speed_mode)
pmf_call_one(pfunc_vdnap0_complete, &args);
if (done)
break;
msleep(1);
usleep_range(1000, 1000);
}
if (done == 0)
printk(KERN_WARNING "cpufreq: Timeout in clock slewing !\n");
@ -236,7 +236,7 @@ static void g5_pfunc_switch_volt(int speed_mode)
if (pfunc_cpu1_volt_low)
pmf_call_one(pfunc_cpu1_volt_low, NULL);
}
msleep(10); /* should be faster , to fix */
usleep_range(10000, 10000); /* should be faster , to fix */
}
/*
@ -281,7 +281,7 @@ static int g5_pfunc_switch_freq(int speed_mode)
pmf_call_one(pfunc_slewing_done, &args);
if (done)
break;
msleep(1);
usleep_range(500, 500);
}
if (done == 0)
printk(KERN_WARNING "cpufreq: Timeout in clock slewing !\n");