linux-kernel - Re: PCI Bursting with PIO

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Message-ID: <4779de450802151000o2c06df0fq6d0daa22c43b935b@mail.gmail.com>
Date:	Fri, 15 Feb 2008 10:00:28 -0800
From:	"Dan Gora" <dan.gora@...il.com>
To:	linux-kernel@...r.kernel.org
Subject: Re: PCI Bursting with PIO

On Fri, Feb 15, 2008 at 5:02 AM, Alan Cox <alan@...rguk.ukuu.org.uk> wrote:
> > Is there any way to get PIO to burst over the PCI bus in the read and
>  > write direction?  My device has 4 BAR registers, but the area where I
>
>  I think you are doign about as well as the X folks did when they spent
>  time on trying to optimise pio transfers to and from graphics card RAM.
>

That's good to know.  Do you have a link or anything to their
discussion or some key words that I could hunt it down?

>
>  > Any ideas would be really appreciated,
>
>  Put a DMA controller on it ;)

Ugh.. sadly that's what's coming.  I really don't get why the
northbridge cannot burst however.  If the memory is mapped
prefetchable and you have to do a PCI read through 3 PCIe bridges to
finally get to your device it seems like it would _really_ behoove the
bridge to do a Memory read multiple and get the whole cache line.  I
have searched around a lot and there doesn't seem to be any info at
all on how you can persuade these bridges to do different PCI commands
or burst.  I don't know why....

thanks again for your help,

dan
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