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>

diff --git a/drivers/cpufreq/pmac64-cpufreq.c b/drivers/cpufreq/pmac64-cpufreq.c
index b977b9aa408e28caf7524a99f006bff390f556e6..889c0d5535722f23b395225be8731ee77ca0ea67 100644 (file)
--- a/drivers/cpufreq/pmac64-cpufreq.c
+++ b/drivers/cpufreq/pmac64-cpufreq.c
@@ -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");