Date: Sun, 18 Dec 2011 02:11:55 -0800 From: Adrian Chadd <adrian@freebsd.org> To: Stefan Bethke <stb@lassitu.de>, Oleksandr Tymoshenko <gonzo@freebsd.org> Cc: "freebsd-embedded@freebsd.org" <freebsd-embedded@freebsd.org> Subject: Re: Updated switch/glue patch? Message-ID: <CAJ-VmokQxQs2DUKL=ONyxnnS7Q28ytmwZJ_thqvc4SvMkmS=cQ@mail.gmail.com> In-Reply-To: <CAJ-VmonvpnaS1rAO%2BsDRh1E5WfsrZTYE297Kc96prhfKjrM89Q@mail.gmail.com> References: <CAJ-Vmon8%2BOXQ4g752zZEB-O0BR0sFWO0QUvw--xp2jsBDkx6tQ@mail.gmail.com> <0F6CC18F-6973-42A2-AC03-F01BF59458AE@lassitu.de> <CAJ-Vmo=Y8pp4iFnw%2B1hcPae6QXFboz=a7puwgC1kVSZ3JwMgPQ@mail.gmail.com> <1100F70E-9DA9-4163-AC9A-423ECE5AA9A3@lassitu.de> <CAJ-VmonrnJ7cC6u2LsL9AGusz_%2BkSwY62Rr1__sg5U_NynJ1SQ@mail.gmail.com> <CAJ-Vmo=WSN1oLM=B2HqSHrWyOaOD9BSwwu8=1Wys0CLRJ_N-TA@mail.gmail.com> <C637C171-A1A2-4296-84FA-6DE97137DC42@lassitu.de> <CAJ-Vmon2boy7OCh_4O0MeCi0yCdZu0OYb5dxHCEK=-%2B46zBGtg@mail.gmail.com> <CAJ-Vmoku5eLEYi5_DXVxK=0=4Ewn2aGepv3YUw4ApuVh_7y2%2Bw@mail.gmail.com> <CAJ-VmonvpnaS1rAO%2BsDRh1E5WfsrZTYE297Kc96prhfKjrM89Q@mail.gmail.com>
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On 18 December 2011 01:54, Adrian Chadd <adrian@freebsd.org> wrote: > Just as a side note - reducing the udelay value from 10 to 1 in my git > tree doesn't stop the huge CPU use. I'm going to next try removing the > locking, as I note that each GPIO access involves a mutex lock and I > bet the witness code is taking a freaking beating here. .. yup. Not compiling in witness helps hugely. I wish I had PMC working at this point - I bet lots of lock overhead would creep up. Basically, a lock is acquired for each GPIO pin set, clear and reconfigure. The gpiobus code itself doesn't do this - that's what gpiobus_lock_bus and gpiobus_unlock_bus is for - but the ar71xx gpio code however does. And so does the gpioiic code - it's locking and unlocking the bus for each scl/sda line operation. Erm, surely that's a bit ridiculous.. surely the locking doesn't need to be that fine grained _and_ multi-levelled. There has to be a better way to do this. :) Adrian
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