Re: [PATCH 2/8] drm/tegra: Allocate BOs from lower 4G when without IOMMU

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On 05.12.2016 20:39, Thierry Reding wrote:
On Thu, Nov 10, 2016 at 08:23:39PM +0200, Mikko Perttunen wrote:
On 64-bit Tegras, buffer object memory allocation may
return memory above 4G that units behind Host1x cannot
access. Add the GFP_DMA flag to these allocation when
IOMMU is not enabled to ensure units can always access
BO memory.

I don't think that's entirely true. The display controller can address
more than 32 bits. It's perhaps slightly different from other units that
are behind host1x, but maybe we need a special case here to allow frame-
buffers to reside in higher memory?

I checked and looks like all (or at least most) units can actually address 34 bits /almost always/. The thing that tripped me up was that apparently the firmware for VIC still needs be in the lower 32 bits. So we should be able to drop this patch.


Thierry


Thanks,
Mikko.
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