Date: Mon, 05 May 2014 09:28:15 -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: <1399303695.22079.239.camel@revolution.hippie.lan> In-Reply-To: <CAJ-Vmo=XmH-RX6_i13NuAXhq-jTC%2BWedGiyOMJaPO4r014DSgw@mail.gmail.com> 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>
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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
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