Re: PCI Burst

[Robert Hancock <hancockr@shaw.ca>]

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@doubledimension.com>
Newsgroups: fa.linux.kernel
To: <linux-kernel@vger.kernel.org>
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@doubledimension.com || pacemakertaker@rock.com }
> ---
>> Failure is not an option; it is included with every Microsoft product.
>
> -
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at  http://www.tux.org/lkml/