Re: [PATCH] 2.5.24 IDE 95 (fwd)

[Bartlomiej Zolnierkiewicz]

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I hope you dont mind Petr.

---------- Forwarded message ----------
Date: Sun, 30 Jun 2002 18:20:03 +0200 (MET DST)
From: Bartlomiej Zolnierkiewicz <[e-mail]>
To: Petr Vandrovec <[e-mail]>
Subject: Re: [PATCH] 2.5.24 IDE 95

Hi!

On Sun, 30 Jun 2002, Petr Vandrovec wrote:

> On Sun, Jun 30, 2002 at 12:53:57AM +0200, Bartlomiej Zolnierkiewicz wrote:
> >
> > Hi Petr!
> >
> > On Sun, 30 Jun 2002, Petr Vandrovec wrote:
> >
> > > Hi,
> > >   I know that IDE95 is broken when it comes to IDE, but... not only
>
> Oops. It should read ... when it comes to CD, ...
> Thanks for your updates, applying them just now.
> 							Petr
>
> P.S.: Locking looks suspicious too. On other side, if hardware is broken
> and requires large data transfers during interrupt, why we should
> bother? ne2000 driver always required disabling interrupts for up to 1.6ms...

1.6ms really bad, masked PIO is about 2ms, this can affect audio etc.,
Legacy/special/broken hardware does only PIO, but most of it do not
require transfers with IRQs disabled (thats why ch->unmask flag).

Even with new locking (ch->lock for everything) we don't have to disable
IRQs completly, we can mask our IRQ and enable rest, but it is not
possible to i.e. share IRQ with audio (because we disable our IRQ).
It was (at least in theory) possible with old locking.

Old locking is that ch->lock spinlock protects access to IDE_BUSY bit in
ch->active, ch->handler and ch->timer. IDE_BUSY protects hardware access,
if it is set we do not enter start_request() in do_request(). When we start
request block layer sets RQ_STARTED flag on request so it is protected
from block layer side. Thats almost all about locking.

Hope this clarifies some things, also old akpm's note about IDE
unmaskirqs attached....

Greets.
--
Bartlomiej

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