[PATCH] iommu/dma: Map scatterlists more parsimoniously

[Daniel Kurtz]

On Thu, Dec 10, 2015 at 8:49 PM, Daniel Kurtz <djkurtz at chromium.org> wrote:
> On Thu, Nov 12, 2015 at 1:47 PM, Yong Wu <yong.wu at mediatek.com> wrote:
>> On Wed, 2015-11-11 at 14:54 +0000, Robin Murphy wrote:
>>> Whilst blindly assuming the worst case for segment boundaries and
>>> aligning every segment individually is safe from the point of view
>>> of respecting the device's parameters, it is also undeniably a waste
>>> of IOVA space. Futhermore, the knock-on effects of more pages than
>
> "Furthermore" (checkpatch actually caught this, not me ;-) )
>
>>> necessary being exposed to device access, additional overhead in page
>>> table updates and TLB invalidations, etc., are even more undesirable.
>>>
>>> Improve matters by taking the actual boundary mask into account to
>>> actively detect the cases in which we really do need to adjust a
>>> segment, and avoid wasting space in the remainder.
>>>
>>> Signed-off-by: Robin Murphy <robin.murphy at arm.com>
>>> ---
>>>
>>> Hi all,
>>>
>>> I've given this some brief testing on Juno with USB and (via magic
>>> PCI hacks) SATA to confirm that all the +1s and -1s at least seem to
>>> be in the right places, so I'm throwing it out now for a head-start on
>>> checking whether it also helps the media folks with the v4l portability
>>> issues they're up against (I'm confident it should). If all goes well I
>>> figure I'll repost next week based on rc1 instead of some random local
>>> development commit.
>>>
>>> Robin.
>>
>> It works well on MT8173. containing
>> VDA/VEA(VideoDecodeAccelerator/VideoEncodeAccelerator) unit test.
>>
>> Tested-by: Yong Wu <yong.wu at mediatek.com>
>
> Reviewed-by: Daniel Kurtz <djkurtz at chromium.org>


Did this patch get lost?
Can we pick it up as a fix for v4.5?