From mboxrd@z Thu Jan  1 00:00:00 1970
From: joro@8bytes.org ('Joerg Roedel')
Date: Fri, 29 Jul 2011 11:35:55 +0200
Subject: [RFC] ARM: dma_map|unmap_sg plus iommu
In-Reply-To: <000301cc4dc4$31b53630$951fa290$%szyprowski@samsung.com>
References: <CAB-zwWjb+2ExjNDB3OtHmRmgaHMnO-VgEe9VZk_wU=ryrq_AGw@mail.gmail.com>
	<000301cc4dc4$31b53630$951fa290$%szyprowski@samsung.com>
Message-ID: <20110729093555.GA13522@8bytes.org>
To: linux-arm-kernel@lists.infradead.org
List-Id: linux-arm-kernel.lists.infradead.org

On Fri, Jul 29, 2011 at 09:50:32AM +0200, Marek Szyprowski wrote:
> On Thursday, July 28, 2011 11:10 PM Ramirez Luna, Omar wrote:

> > 2. tidspbridge driver sometimes needs to map a physical address into a
> > fixed virtual address (i.e. the start of a firmware section is expected to
> > be at dsp va 0x20000000), there is no straight forward way to do this with
> > the dma api given that it only expects to receive a cpu_addr, a sg or a
> > page, by adding iov_address I could pass phys and iov addresses in a sg
> > and overcome this limitation, but, these addresses belong to:
> 
> We also encountered the problem of fixed firmware address. We addressed is by
> setting io address space start to this address and letting device driver to
> rely on the fact that the first call to dma_alloc() will match this address.

This sounds rather hacky. How about partitioning the address space for
the device and give the dma-api only a part of it. The other parts can
be directly mapped using the iommu-api then.

Regards,

	Joerg
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