Hi,

On Thu, 2018-11-15 at 23:35 +0800, Chen-Yu Tsai wrote:

On Thu, Nov 15, 2018 at 10:51 PM Paul Kocialkowski
[off-list ref] wrote:

quoted

This adds nodes for the Video Engine and the associated reserved memory
for the H5. Up to 96 MiB of memory are dedicated to the CMA pool.

The pool is located at the end of the first 256 MiB of RAM so that the
VPU can access it. It is unclear whether this is still a hard
requirement for this platform, but it seems safer that way.

I think we can actually test this. You could move the reserved memory
pool beyond 256 MiB, and have cedrus decode stuff, and try to display
the results. If it's gibberish, or the system crashes, it's likely the
memory access wrapped around at 256 MiB.

What do you think?

I did the test on various platforms and found that starting with the
A33, the VPU can map any address in RAM! SO we shouldn't need reserved
memory nodes for these devices after all.

Cheers,

Paul

-- 
Paul Kocialkowski, Bootlin (formerly Free Electrons)
Embedded Linux and kernel engineering
https://bootlin.com