RE: [PATCH v2 7/9] dpaa_eth: fix iova handling for contiguous frames

[Laurentiu Tudor]

> -----Original Message-----
> From: Christoph Hellwig <hch@xxxxxxxxxxxxx>
> Sent: Saturday, April 27, 2019 7:46 PM
> 
> On Sat, Apr 27, 2019 at 10:10:29AM +0300, laurentiu.tudor@xxxxxxx wrote:
> > From: Laurentiu Tudor <laurentiu.tudor@xxxxxxx>
> >
> > The driver relies on the no longer valid assumption that dma addresses
> > (iovas) are identical to physical addressees and uses phys_to_virt() to
> > make iova -> vaddr conversions. Fix this by adding a function that does
> > proper iova -> phys conversions using the iommu api and update the code
> > to use it.
> > Also, a dma_unmap_single() call had to be moved further down the code
> > because iova -> vaddr conversions were required before the unmap.
> > For now only the contiguous frame case is handled and the SG case is
> > split in a following patch.
> > While at it, clean-up a redundant dpaa_bpid2pool() and pass the bp
> > as parameter.
> 
> Err, this is broken.  A driver using the DMA API has no business
> call IOMMU APIs.  Just save the _virtual_ address used for the mapping
> away and use that again.  We should not go through crazy gymnastics
> like this.

I think that due to the particularity of this hardware we don't have a way of saving the VA, but I'd let my colleagues maintaining this driver to comment more on why we need to do this.

---
Best Regards, Laurentiu