From: Peter Barada <peterb@logicpd.com>
To: linux-omap <linux-omap@vger.kernel.org>
Subject: hrtimer_nanosleep() weirdness...
Date: Fri, 16 Oct 2009 15:37:47 -0400 [thread overview]
Message-ID: <1255721867.19793.311.camel@blitz> (raw)
I'm using an hrtimer in my tsc2004 touch driver to sleep between samples
for 7.5mSec. Here's the essence of the inner loop that grabs samples:
for (;;) {
// Get a point, pass it to input_report_abs...
pen_is_down = tsc2004_get_point(d);
// If pen is up up, then break out
if (!pen_is_down || signal_pending(tsk))
break;
{
struct timespec timeout;
// sleep for 7.5 mSec (giving max 133 touch/sec)
timeout = ns_to_timespec(75 * 100 * 1000);
hrtimer_nanosleep(&timeout, NULL, HRTIMER_MODE_REL, CLOCK_MONOTONIC);
}
}
What's really strange is when I use ts_test to measure sample rate, I
see:
OMAP-Torpedo# export TSLIB_TSDEVICE=/dev/input/event0
OMAP-Torpedo# export TSLIB_CONSOLEDEVICE=none
OMAP-Torpedo# ts_test
717.804687: 176 161 234
717.813446: 176 161 234
717.822265: 176 160 234
717.993255: 178 159 234
718.002014: 179 158 234
718.188537: 180 158 234
719.015441: 181 157 234
719.165100: 181 157 234
719.360412: 182 157 234
719.369079: 182 157 234
719.438537: 182 156 234
719.555725: 182 156 234
719.564392: 182 156 234
719.751037: 180 155 234
719.768432: 179 155 234
719.777099: 178 154 234
719.946350: 174 150 234
720.000976: 175 144 234
720.141662: 184 140 234
720.336975: 189 138 234
720.490722: 195 137 234
720.499420: 198 138 234
720.858123: 198 139 234
720.922912: 198 139 234
721.126922: 198 139 234
721.135620: 198 139 234
721.144317: 198 139 234
721.152984: 198 139 234
721.161682: 198 139 234
721.313537: 198 139 234
721.438537: 198 138 0
Which shows over 3.63 seconds 33 samples, or only 9.08 samples/second,
including a max delay of .827 seconds (719.015441 - 718.188537).
But if I "ifup eth0" to bring the networking up (and nothing else is
running), I get:
OMAP-Torpedo# ifup eth0
[sleeping 5s]...net eth0: SMSC911x/921x identified at 0xc8858000, IRQ:
289
eth0: link down
eth0: link up, 100Mbps, full-duplex
udhcpc (v1.15.1) started
Sending discover...
Sending select for 192.168.3.151...
Lease of 192.168.3.151 obtained, lease time 86400
deleting routers
route: SIOCDELRT: No such process
adding dns 192.168.3.1
OMAP-Torpedo# ts_test
735.615905: 263 140 234
735.615905: 263 140 234
735.625152: 261 141 234
735.634277: 260 141 234
735.643463: 260 141 234
735.652648: 260 142 234
735.661865: 261 142 234
735.671081: 262 141 234
735.680267: 263 141 234
735.689453: 264 140 234
735.698669: 265 139 234
735.707885: 266 139 234
735.717102: 267 138 234
735.726318: 268 138 234
735.735534: 268 138 234
735.744751: 269 137 234
735.762725: 269 137 234
735.771942: 270 137 234
735.790344: 270 136 234
735.799560: 270 136 234
735.808746: 270 136 234
735.817962: 270 136 234
735.845611: 270 136 234
735.910217: 270 136 234
735.919403: 270 136 234
735.928588: 271 136 234
735.937866: 271 136 234
735.947082: 271 136 234
735.955871: 271 136 234
735.974334: 271 136 234
735.983551: 270 136 234
736.001220: 270 136 234
736.010467: 270 136 234
736.047302: 270 136 234
736.056488: 270 136 234
736.074951: 270 137 234
736.093383: 269 137 234
736.102600: 269 137 0
Or 36 samples in 0.486695 seconds -> ~74 samples per second with an
average/deviation that is much more acceptable.
This is completely reproducible.
Any ideas why firing up the SMSC911x driver would cause
hrtimer_nanosleep() to be much more predictable?
--
Peter Barada <peterb@logicpd.com>
Logic Product Development, Inc.
next reply other threads:[~2009-10-16 19:32 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-10-16 19:37 Peter Barada [this message]
2009-10-17 7:53 ` hrtimer_nanosleep() weirdness michael
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