Date: Wed, 06 Feb 2013 08:16:29 +0000 From: Iain Young <iain@g7iii.net> To: Ian Lepore <ian@FreeBSD.org> Cc: freebsd-arm@FreeBSD.org Subject: Re: SD card -image- for the beaglebone Message-ID: <5112115D.5040709@g7iii.net> In-Reply-To: <1360124308.93359.557.camel@revolution.hippie.lan> References: <510A4F5B.7000407@g7iii.net> <1359646574.93359.327.camel@revolution.hippie.lan> <510AE1D6.8010203@g7iii.net> <1360124308.93359.557.camel@revolution.hippie.lan>
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On 06/02/13 04:18, Ian Lepore wrote: > Check out what I taught my beaglebone to do today... > > root@bb:/ # ntpq -p > remote refid st t when poll reach delay offset jitter > ========================================================================== > oPPS(0) .PPS. 0 l 4 16 377 0.000 0.399 0.008 > +dvb.hippie.lan .GPS. 1 u 55 64 377 1.411 0.666 0.126 > +tflex.hippie.la .GPS. 1 u 15 64 377 0.901 1.867 0.904 > +paranoia.hippie .PPS. 1 u 61 64 377 0.396 0.426 0.025 > xutcnist2.colora .ACTS. 1 u 71 64 376 34.136 -11.277 4.656 > xnist1.symmetric .ACTS. 1 u 63 64 377 59.880 12.327 2.113 > -ntp.your.org .CDMA. 1 u 4 64 377 51.185 -4.212 4.215 > xntp1.conectiv.c .IRIG. 1 u 51 64 377 99.067 17.784 3.445 > > It turns out the chip has nice timer hardware that can latch the > freeruning timercounter in response to the PPS signal. That allows for > a PPS driver that doesn't use interrupts at all. The timecounter code > has a specific interface for such hardware, but there isn't much example > code in the base for how to use it. Soon there'll be more. :) > > I'll attach a patch in case anyone else wants to play with this. To use > it, apply the patch, add "options PPS_SYNC" to the kernel config, and > choose which timer pin you want to put the pps on. The attached patch > uses the timer4 pin, which is exposed on the P8 connector as pin #7. > You can use any of the timer4-timer7 pins, just set the one you want to > use to "input" in the dts and the driver will use it. Thanks for that, looks great, and very interesting. I'll do more than play with it (well when the 8 Gig card arrives anyway!) First thought, extending for multiple PPS :) [Because I can :P] Hopefully come the weekend I can rebuild the kernel using Tim's 8 Gig image, with this patch, and some more bits in the dts. Oh, and test with PHKs ntpns on DCF-77, assuming that module arrives as well. All the Best Iain
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