Re: Linux 2.4.21-pre3-ac4

From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Alan Cox <alan@redhat.com>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: Linux 2.4.21-pre3-ac4
Date: 12 Jan 2003 20:51:14 +0100	[thread overview]
Message-ID: <1042401074.525.219.camel@zion.wanadoo.fr> (raw)
In-Reply-To: <1042403235.16288.14.camel@irongate.swansea.linux.org.uk>

On Sun, 2003-01-12 at 21:27, Alan Cox wrote:

> which currently has two problems Ross found
> 
> 1.  The processors or so fast we have to enforce the 400nS delay nowdays

What about PCI write posting ? How can we enforce the 400ns delay here ?
I suspect we can't read back from the taskfile registers after writing
the command. Especially when using DMA, I think I remember Andre telling
me even tapping alt status might not be safe... So we need to issue
a read from the same bus path, but not on any taskfile register from
this channel... hrm... any idea ?

> 2.  The code is racey in some situations with a shared IRQ because we
> may get an IRQ after we set the handler but before we send the command,
> or implemnted the other way the command can complete before we set the
> handler.

Yup, that's an old problem indeed.

Ben.