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

From: David Hawkins
Date: Mon Apr 27 2009 - 16:41:51 EST


Hi Timur,

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."

Ok, thanks.

Ira will add your comment to the body of the code near
the PRC_RM command and submit a new patch.

Cheers,
Dave

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