Subject: Re: [PATCH] fsldma: use PCI Read Multiple command

From: Timur Tabi <[email-masked]>
Date: Mon, 27 Apr 2009 15:26:36 -0500

David Hawkins wrote:

> PRC_RM - PCI read multiple
>    The default PCI read command used by the DMA controller is
>    PCI Read (PCI command 6h). When the burst length is 32-bytes
>    or longer, PCI Read Line (PCI command Eh) is used (undocumented
>    feature of the controller). Using PCI read multiple
>    (PCI command Ch) results in high-performance across PCI
>    bridges. DMA transfers to non-prefetchable PCI registers
>    should not result in prefetched reads, even when using
>    the PCI read multiple command.

I was thinking more along the lines of:

"This driver tells the DMA controller to use the PCI Read Multiple
command, instead of the PCI Read Line command, for PCI read operations.
 Please be aware that this setting may result in read pre-fetching on
some platforms."

-- 
Timur Tabi
Linux kernel developer at Freescale