Date: Mon, 05 May 2014 09:35:57 -0600 From: Ian Lepore <ian@FreeBSD.org> To: Adrian Chadd <adrian@FreeBSD.org> Cc: "freebsd-arm@freebsd.org" <freebsd-arm@FreeBSD.org> Subject: Re: USB isochronous traffic with Rasberry Pi [WAS: Re: USB audio device on Raspberry Pi] Message-ID: <1399304157.22079.243.camel@revolution.hippie.lan> In-Reply-To: <1399303695.22079.239.camel@revolution.hippie.lan> References: <20140425154430.GA76168@utility-01.thismonkey.com> <535A8AEA.1000100@selasky.org> <20140425204134.GA458@cicely7.cicely.de> <20140430091411.GA45015@utility-01.thismonkey.com> <5360C0A7.9010407@selasky.org> <1398867266.22079.51.camel@revolution.hippie.lan> <CAGW5k5bZ_bTQUXuzNm=tbwx3npz1_HoOR3vM8TBRVFs8zWCq-w@mail.gmail.com> <5362638B.1080104@selasky.org> <5363C133.2000304@selasky.org> <53677CB8.5000800@selasky.org> <CAJ-Vmo=XmH-RX6_i13NuAXhq-jTC%2BWedGiyOMJaPO4r014DSgw@mail.gmail.com> <1399303695.22079.239.camel@revolution.hippie.lan>
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On Mon, 2014-05-05 at 09:28 -0600, Ian Lepore wrote: > On Mon, 2014-05-05 at 08:18 -0700, Adrian Chadd wrote: > > evil idea: > > > > #define DELAY(ms) _DELAY(ms, __FILE__, __LINE__) > > > > .. then modify the relevant arm delay function to take FILE/LINE and > > KTR log it. :-) > > > > > > -a > > Except some uart console output routines are structured like > > while (!readreg(STATUS) & TXRDY) > DELAY(n); > > I don't know why people think that calling delay in busy loops like that > has any value, considering that DELAY is almost always implemented as > some form of > > while (readreg(COUNTER) < target_count) > ; > > I guess maybe it has value only in that it helps you find busy-loops. > I'd rather that we had a function just for that purpose, like > > while (readreg(COUNTER) < target_count) > cpu_busy_loop(); > > (We have something like that that's x86-specific, iirc). > > -- Ian Oh never mind, I just noticed you said KTR, not printf. -- Ian
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