śr., 13 lut 2019 o 07:36 H. Nikolaus Schaller <hns@xxxxxxxxxxxxx
<mailto:hns@xxxxxxxxxxxxx>> napisał(a):
Hi Tony,
> Am 13.02.2019 um 01:41 schrieb Tony Lindgren <tony@xxxxxxxxxxx
<mailto:tony@xxxxxxxxxxx>>:
>
> Hi,
>
> * Philipp Rossak <embed3d@xxxxxxxxx <mailto:embed3d@xxxxxxxxx>>
[190212 22:25]:
>> I'm looking now into that PVR SGX driver since a while. I
already reworked
>> that old "opensource" driver to work with a quite new kernel
(4.16 or 4.17)
>> [But that code got lost].
>> For the sunxi devices this was only a short coding session to
get that
>> running. For OMAP this might be easier/faster since the general
linux
>> situation is better.
>
> So a git repo that works for omaps and sunxi would be a good
> start then :)
>
>> I'm not sure if we are able to provide a generic driver since
there are
>> different userspace versions that are only compatible with
their own kernel
>> driver. Not all compile flags for the kernel driver work with
all userspace
>> lib versions, at least on sunxi. Be aware that there are also
different
>> versions of those GPU ip cores and all have different features
and bug
>> fixes.
>
> No doubt it's a mess.. I'm only suggesting a generic driver that
> manages standard Linux resources like regulators, clocks and
> interrupts and provides 2d acceleration for sgx540 based on what
> we already have at drivers/gpu/drm/gma500/accel_2d.c. The idea
> being that it might then also make dealing with the rest of the
> sgx blobs a bit easier hopefully.
Well, ok.
So you suggest that we e.g. take the omap SoC support in
http://git.goldelico.com/?p=letux-kernel.git;a=tree;f=drivers/staging/pvr/1.14.3699939/eurasia_km/services4/system/omap;h=09ff9c9112dd7e8f7316ba5f1e022dcb824c2ce4;hb=1d5b6a91eca80168c37ecb66157e675d28666652
and make an "eurasia_km / services4 / system / generic" out of
it using the 2d functions?
Please take a look into especially sysconfig.c and SysInitialise()
which does the lion's share of initialization if it can be rewritten
to become generic.
>
>> If you reach a good state with that driver, I can try to port
that to sunxi.
>> Is there any good/cheap OMAP4/5 Devboard you can recommend?
>
> Hmm so the n900 folks have the sgx blobs working with recent
> mainline kernels for sgx530 I believe, and Nikolaus is close to
> having the sgx blobs working for sgx540.
Also for sgx530 with recent kernel. The blobs itself are working, it
is just missing code to tell the SGX module where the framebuffer
is located in virtual memory.
I think setting
CONFIG_DRM_FBDEV_OVERALLOC=700
in my case (like old kernel) this will make powervr driver allocate
one framebuffer + 2 backbuffers
and
CONFIG_DRM_FBDEV_LEAK_PHYS_SMEM
it should make it working. On my device i had to use different "fix"
https://github.com/PabloPL/linux/commit/d0b1df4067a724aa0b38d11c82fd3ff0958a45a6
The physical address of fb is used in driver (and passed to
userspace?). It's code is here for my device
https://github.com/PabloPL/linux/blob/powervr/drivers/gpu/drm/powervr/s3c_lcd/s3c_displayclass.c#L943
And here is simple devicetree entry which is read by driver (it was
added by person which is also working on mainlining my device).
https://github.com/PabloPL/linux/blob/powervr/arch/arm/boot/dts/s5pv210-aries.dtsi#L325
But this still didn't allowed me to run egl code with that driver.
Probably i'll need to get logs from old kernel.
All my code is currently (if someone is interested ) in
https://github.com/PabloPL/linux/tree/powervr
> I may not be aware of
> the current status though.
>
> For a devboard with sgx540, you should be able to find one for
> few tens of units for a used pandaboard-es for example or
> somebody here might even have an old one to donate. If you feel
> like playing with a phone, droid 4 xt894 is somewhat usable
> with mainline kernels with pending patches for LCD and modem,
> no idea what the sgx540 status on it might be. Pyra handheld
> is not yet available except for prototypes. And then on
> beagleboard-x15 there's sgx544, and beaglebone has sgx530
> FYI so that might not help if you need sgx540.
>
>> Don't expect any support from TI or IMG. TI can't support a
project like
>> this, since they don't own the code and IMG is not willing to
support.
>
> Yeah that we've seen already over past 10 or so years :)
>
>> An other big issue is the leaked SGX source code [1]. So I
think it would be
>> better to start a clean room reverse engineering project. I'm
already
>> working on that.
>
> OK so we're discussing at least three projects then:
>
> 1. A git repo that allows sgx blobs to work for various
> SoCs with current mainline kernels
Yes.
>
> 2. A generic 2d sgx540 driver based on existing mainline
> kernel drivers/gpu/drm/gma500/accel_2d.c
May be needed or not.
>
> 3. Your reverse engineering project that might help
> with figuring out how things are supposed to work
IMHO a completely separate project.
Basically there is a strict layering:
L4 user-space libraries
L3 SGX firmware
L2 SGX firmware loader
L1 SoC glue (clock, reset, dma, virtual memory, ...)
I am mainly considering L1 here and fixing L2. L1 is SoC
specific of course and L2 needs Linux-release specific patches.
L2-L4 depend on SGX version.
L2 contains a lot of #ifdef that depend on SGX530/540/544 and even
more.
Reverse engineering addresses L3 and L4.
Of course if will be is successful it might become possible to improve
the whole L1-L4 stack, but that is another 10 years in the future :)
Since it is such a big task, I would propose to start with something
close to working (some TI/IMG DDK) and improve on that instead of
starting with parts from scratch.
BR,
Nikolaus
