slow probe for ata channel with only an atapi master on it

[Bruce Evans]

[Private reply]

[I wrote]
> The other drive is undead.  It seems to fail to spin up sometimes, but
> works perfectly if its probe succeeds and I start accessing it immediately,
> but tends to fail if I don't access it for a while.  It now always fails
> overnight.  I'm wondering if it spins down and then the spin up doesn't
> work, and plan to try putting it in sleep modes intentionally.  The

I tried your "atacontrol sleep" command.  It broke the drive in much the
same way as not using it overnight, except the BIOS was able to wake
it up correctly :-).  "atacontrol standby" doesn't break it.

> driver handles its failure poorly.  The failure is usually hard (takes
> several power cycles to recover from), to it gets "removed from
> configuration" after several seconds or minutes of the system being
> unusable because it is blocked on Giant.  Then removal usually causes
> a null pointer panic.

"atacontrol detach" also puts the drive too sleep, and it works much
better than shooting an active drive.  It also works to help wake up the
drive: the drive works right after "atacontrol sleep; atacontrol detach;
atacontrol attach", except it takes about 5 seconds to wake up after
the first i/o command (attach apparently doesn't wake it up).

Bruce