Re: problem with blk_queue_bounce_limit()

Russell King
2003-06-07T09:31:13Z

On Sat, Jun 07, 2003 at 12:20:46AM -0700, David Mosberger wrote:
> ./include/asm-arm/pci.h:#define PCI_DMA_BUS_IS_PHYS (0)

I suspect we probably set this incorrectly; we have some platforms where
there is merely an offset between the phys address and the bus address.
For these, I think we want to set this to 1.

Other platforms require the dma functions to allocate a new buffer
and copy the data to work around buggy "wont fix" errata (eg, new buffer
below 1MB) and for these I think we want to leave this at 0.

It is rather unfortunate that this got called "PCI_xxx" since it has
been used in a non pci-bus manner in (eg) the scsi layer.

Also note that I have platforms where the dma_mask is a real mask not
"a set of zeros followed by a set of ones from MSB to LSB." I can
see this breaking the block layer if PCI_DMA_BUS_IS_PHYS is defined
to one. 8/

--
Russell King (rmk@arm.linux.org.uk) The developer of ARM Linux