Re: PCI Burst

[Robert Hancock]

Two things that I'd check, that the memory range shows up as prefetchable 
(i.e. in lspci) and also that the memory region is mapped with ioremap and 
not ioremap_nocache. Also, what's the region defined as in /proc/mtrr? I 
think it has to be mapped as write-back for burst reads to work. When the 
CPU reads in a cache line in that memory range from the bus, that should 
hopefully get passed through as a burst read on the PCI bus, but that may be 
chipset-dependent.

Getting PIO-mode PCI reads and writes like this to work efficiently seems a 
rather difficult thing to do..


----- Original Message ----- 
From: "Brian McGrew" <Brian@xxxxxxxxxxxxxxxxxxx>
Newsgroups: fa.linux.kernel
To: <linux-kernel@xxxxxxxxxxxxxxx>
Sent: Thursday, September 23, 2004 7:22 PM
Subject: PCI Burst


> Running RedHat 7.3 with the 2.4.20 kernel.
>
> How do I enable PCI burst mode for reading and writing on the PCI bus?  We 
> mmap 128MB per board that we install and now that we've added our 
> addressing to the /proc/mtrr file, we can burst on write but we're not 
> seeing any burst on the read.
>
> Any ideas?
>
> -brian
>
> Brian D. McGrew {brian@xxxxxxxxxxxxxxxxxxx || pacemakertaker@xxxxxxxx }
> ---
> > Failure is not an option; it is included with every Microsoft product.
>
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