linux-kernel - Re: dma_alloc_coherent() on PPC32: physical addresses above 2G possible?

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Date:	Sun, 20 Jul 2008 21:25:51 +0200
From:	Stefan Richter <stefanr@...6.in-berlin.de>
To:	Arjan van de Ven <arjan@...radead.org>
CC:	linuxppc-dev@...abs.org, linux-kernel@...r.kernel.org
Subject: Re: dma_alloc_coherent() on PPC32: physical addresses above 2G possible?

Arjan van de Ven wrote:
> On Sun, 20 Jul 2008 20:36:23 +0200
> Stefan Richter <stefanr@...6.in-berlin.de> wrote:
> 
>> PS:  I don't want to set the DMA mask of this device to
>> DMA_31BIT_MASK because that would be detrimental to other functions
>> of the device. It's a TI TSB43AB22A FireWire controller.
> 
> Hi,
> 
> just want to mention that you can set the coherent mask separately from
> the generic mask... is that sufficient for your load?
> (you can even set it just for this allocation..)

Hmm.  Would that be done this way?
During probe:

	if (chip_is_tsb43ab22a) {
		if (dma_supported(dev, DMA_31BIT_MASK))
			chip->needs_dma_mask_workaround = 1;
		else
			chip->needs_some_other_workaround = 1;
	}

Later on:

	if (dev->needs_dma_mask_workaround)
		pci_set_consistent_dma_mask(pdev, DMA_31BIT_MASK);
	allocate_something_special;
	if (dev->needs_dma_mask_workaround)
		pci_set_consistent_dma_mask(pdev, DMA_32BIT_MASK);

Or is there a variant of dma_alloc_coherent() which directly accepts a
mask argument?
-- 
Stefan Richter
-=====-==--- -=== =-=--
http://arcgraph.de/sr/
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