On 10/11/2021 10:29, Ivaylo Dimitrov wrote:
Hi,
On 9.11.21 г. 11:22 ч., Tomi Valkeinen wrote:
Hi,
On 08/11/2021 19:43, Ivaylo Dimitrov wrote:
Sorry, mail was sent to the old Tomi's address.
On 8.11.21 г. 19:05 ч., Ivaylo Dimitrov wrote:
Hi,
Currently omapdrm supports TILER rotation only, which excludes omap3
and earlier SoCs. I have the hardware (N900/N950), time and will to
implement VRFB rotation support in omapdrm driver, however, I'll
appreciate some hints. Or, if there is already something ready,
please point me to it so I can take it from where it is.
Besides partially reverting 517a8a9564c0dea98e6d4e2c7f0fe4cbb9b8c9ba
and copying VRFB code from omapfb, is there anything else I shall
take in consideration? Or, VRFB driver should not be a part of
omapdrm, but a standalone one?
We already have DMM driver in the omapdrm module, and I think VRFB
fits along just fine. I don't think there ever has been any other
users for VRFB than DSS, and as it's such an old IP, I don't think
there ever will.
Ok, I guess if a need appears, it can always be moved out of omapdrm.
The same applies to DMM/TILER code I guess.
Yes.
I don't have any particular hints in mind.
Do you have omap4/5 so you can test that DMM still works after your
changes?
So, first, a few clarifications about DMM/TILER. There are two somewhat
separate things. I'm not sure what are the exactly correct words for
these, but these are the terms I've used:
- DMM (sometimes called wrongly TILER 1D), which acts as a basic iommu.
It doesn't do rotation, just mapping scattered pages to a contiguous
memory view.
- TILER (or TILER 2D) which on top of the above, adds support for rotation.
Yes, I have motorola droid4 (4430/sgx540) to test with. Which brings
another issue on the table - I was not able to find a way to allocate a
TILER dma_buf. The only way seems to be by using omap_bo_xxx functions,
which is a 'vendor' API. Do I miss something or omapdrm is lacks
Yes, omap_bo_xxx is omap specific API. But I don't understand your
question about omapdrm. omap_bo functions use omapdrm's API. The
userspace can skip libdrm and just call the ioctls directly if they so want.
functionality? Also, is there any particular reason why TILER is not
enabled by default for dma_buf BOs? Is it a limited resource (like,
there is a finite number of BOs that can use TILER) or there is some
Yes, TILER is a limited resource, there's a maximum size for the
currently mapped memory. Going through TILER is also slower, and while
for 0 degree rotation the diff probably isn't much, it's still there.
Also TILER is not really quite supported, as I never got it working with
all the YUV modes, and also because there's a HW issue, which may cause
the device to lock up in some rare cases. And last, TILER creates such a
memory layout that it's not possible to share it safely with dmabuf, as
dmabuf lacks the features to properly describe the layout.
All that said, I think TILER should mostly work in upstream.
However, DMM is supported, and used by default. If you allocate a dumb
buffer, it uses DMM by default.
other reason. Also, is it possible to 'migrate' non-TILER BO to a TILER
one? The same issue will arise with VRFB (with its 12 contexts on omap3)
as well.
No, not possible to migrate.
So, in short:
- omap3: VRFB driver to be added to omapdrm.
- omap3/omap4/omap5: dma_buf lacks TILER/VRFB support
Can you elaborate on what's missing?
Adding VRFB should be trivial, but I am more concerned about how to
rotate dma_buf buffers. I imagine something like - on setting the plane
"rotate" property, migrate physical address from 'normal' CMA memory to
a TILER/VRFB one. Is that possible? What if we already have that bo
mmap-ed? What if SGX MMU is already set up to access the memory? Or, is
it possible to use TILER for read access, the same way VRFB can be
set-up, so instead of writing through TILER/VRFB, DSS to be set-up to
read FB memory through TILER/VRFB thus avoiding the need to migrate SG
and/or page tables?
I have to say I don't quite remember how VRFB works. But for TILER, we
have to specifically allocate a TILER buffer. And then everyone else
uses TILER 0 degree view, but DSS can use 0/90/180/270 view when showing
it on the display.
But I think the case is the same for VRFB too: if you want to use VRFB,
all access has to go through VRFB, as the pixels are written to memory
in a special way.
Tomi
