Date: Tue, 2 Apr 1996 05:06:24 +1000 From: Bruce Evans <bde@zeta.org.au> To: Brett_Glass@ccgate.infoworld.com, freebsd-hackers@freebsd.org, freebsd-hardware@freebsd.org Subject: Re: Hacked kernel with option to disable "green" mode Message-ID: <199604011906.FAA00611@godzilla.zeta.org.au>
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>ftp://ftp.seagate.com/techsuppt/misc/no_idle.zip >on Seagate's Web site. Essentially, to turn off the "green mode" >inactivity timer, one issues controller command 0xFB for the relevant >drive, with a 0 in the controller's sector count register, during >initialization. (A number larger than zero sets the timer to that number of >milliseconds.) 0xFB is vendor specific according to the (old) ata-r4c draft. That standard has a lot about sleep, standby and idle modes, but only host- controlled modes. >I'm not a UNIX kernel hacker (or I wasn't, anyway), and was utterly >unfamiliar with all the conventions used in FreeBSD, so the source in >wd.c took quite a while to analyze. (It's much more complex than it needs >to be, and uses -- Aargh! -- uninterruptible busy-waits at the kernel >level. THIS is why the entire OS freezes for seconds at a time.) After It's much less complex than it needs to be :-). >[Aside: Maybe, at the same time, someone could tell me what the SLEEPHACK >configuration bit does. It looks as if it's supposed to make the driver >more tolerant of drive spindowns on laptops, but I'm not sure that it will >work as advertised. On this machine, the unwedge() function, which it >calls, also complains when the disk spins down.] It just forces a wdunwedge() call if the drive is unexpectedly busy in wdcommand(). wdunwedge() might fail because TIMEOUT is too short. It should be at least 31000000 (31 seconds). Bruce
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