Re: [PATCH 2/3] ARM: qcom_defconfig: enable MSM IOMMU for display

[Rob Clark]

On Mon, Nov 27, 2017 at 9:34 AM, Jonathan NeuschÃfer
<j.neuschaefer@xxxxxxx> wrote:
> Hi,
>
> On Mon, Nov 27, 2017 at 11:44:57AM +0000, srinivas.kandagatla@xxxxxxxxxx wrote:
>> From: Srinivas Kandagatla <srinivas.kandagatla@xxxxxxxxxx>
>>
>> MSM IOMMU is required for apq8064 display, so enable it by default.
>
> What exactly do you mean by "display"? Which ip block requires IOMMU
> support?
>

display block in apq8064 is mdp4 (drivers/gpu/drm/msm/mdp/mdp4)..
technically it can use iommu in bypass mode w/ physically contiguous
memory, but no one wants to do that, if they don't have to.  The gpu
does have a hard requirement on iommu.

BR,
-R