[lkml]   [2003]   [Feb]   [16]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: [0/4][via-rhine] Improvements
> On Sat, 15 Feb 2003, Roger Luethi wrote:
> >
> > Thanks for raising that issue. It is my understanding that PIO ops are
> > synchronous (on IA-32). If that is correct, problems should only occur if
> > the driver is built with MMIO support, no?
> No, even PIO ops are asynchronous. They are _more_ synchronous than the
> MMIO ones (I think the CPU waits until they hit the bus, and most bridges

Hmmm... A recent thread on PCI write posting seemed to confirm my view [1].
What am I missing here?

------------------------------ cut here -----------------------------------
From: Alan Cox <>
Subject: Re: Linux 2.4.21-pre3-ac4
Date: 12 Jan 2003 20:40:54 +0000

On Sun, 2003-01-12 at 19:51, Benjamin Herrenschmidt wrote:
> What about PCI write posting ? How can we enforce the 400ns delay here ?

For i/o space it is ok as in*/out* are synchronous. For mmio right now I
don't know. I need to talk to Andre about that for SATA. I guess for the
PPC its going to be fun

------------------------------ cut here -----------------------------------

> don't need a IO read to force it out. But considering the wide variety of
> PCI bridges out there I bet there are some that will post even PIO writes
> and might hold on to them for some time, especially if other activity like
> DMA keeps the bus busy.

There was some talking about hwif->IOSYNC() (for IDE). That might be
interesting for other devices, too. It could resolve to a nop for
synchronous operations, and say a read* for MMIO. IMHO it shouldn't be up
to a driver maintainer to figure out what sync op some arch the driver may
run on needs. What a maintainer typically _can_ provide is type of
operation (MMIO/PIO) and a register that is considered safe for a sync


To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to
More majordomo info at
Please read the FAQ at

 \ /
  Last update: 2005-03-22 13:33    [W:0.039 / U:24.236 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site