Date: Tue, 25 Nov 2014 09:52:41 +0100 From: =?utf-8?Q?Dag-Erling_Sm=C3=B8rgrav?= <des@des.no> To: Mark R V Murray <mark@grondar.org> Cc: arch@freebsd.org, Ian Lepore <ian@FreeBSD.org> Subject: Re: svn commit: r274739 - head/sys/mips/conf Message-ID: <8661e3wtk6.fsf@nine.des.no> In-Reply-To: <F60907B5-433F-4800-82B4-5D882AF0B3BB@grondar.org> (Mark R. V. Murray's message of "Tue, 25 Nov 2014 07:53:51 %2B0000") References: <201411200552.sAK5qnXP063073@svn.freebsd.org> <20141120084832.GE24601@funkthat.com> <AE8F2D30-7F91-4C90-B79A-D99857D8AED8@grondar.org> <20141121092245.GI99957@funkthat.com> <1416582989.1147.250.camel@revolution.hippie.lan> <026FEB8A-CA8C-472F-A8E4-DA3D0AC44B34@grondar.org> <1416596266.1147.290.camel@revolution.hippie.lan> <F017033A-B761-4435-A7F8-264D2F4662A0@grondar.org> <1416598889.1147.297.camel@revolution.hippie.lan> <86egsvueqk.fsf@nine.des.no> <1416691274.1147.339.camel@revolution.hippie.lan> <398A380D-49AF-480C-8842-8835F81EF641@grondar.org> <1416806894.1147.362.camel@revolution.hippie.lan> <18B8A926-59C0-49B4-ADA3-A11688609852@grondar.org> <1416841268.1147.386.camel@revolution.hippie.lan> <CC6B67E1-55A2-4952-AB43-5F6C787F629B@grondar.org> <86wq6k9okk.fsf@nine.des.no> <F60907B5-433F-4800-82B4-5D882AF0B3BB@grondar.org>
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Mark R V Murray <mark@grondar.org> writes:
> How two consecutive calls to get_cyclecount() can repeatedly return
> such massive numbers is an indication that something has gone badly
> wrong.
No, wait. I looked at the code. The most likely explanation is that it
is falling through to this:
binuptime(&bt);
return ((uint64_t)bt.sec << 56 | bt.frac >> 8);
so the top 8 bits are seconds (meaning that get_cyclecount wraps around
every 256 seconds) and the bottom 64 are the base 2 fractional part. At
first glance, Ian's number seem to be identical from one run to the
next, but they're not - there seems to be a small amount of variation.
But I'm still very suspicious of at91_st0, which is constant, and
nexus0, at91_aic0 and at91_pmc0, which are constant *and* identical.
DES
--=20
Dag-Erling Sm=C3=B8rgrav - des@des.no
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