[Mesa-dev] 10-bit Mesa/Gallium support

[Mario Kleiner]

On 11/23/2017 06:45 PM, Ilia Mirkin wrote:
> On Thu, Nov 23, 2017 at 12:35 PM, Marek Olšák <maraeo at gmail.com> wrote:
>> Hi everybody,
>>
>> Mario, feel free to push your patches if you haven't yet. (except the
>> workaround)
>>

Hi,

just started 10 minutes ago with rebasing my current patchset against 
mesa master. Will need some adjustments and retesting against i965.

I was also just "sort of done" with a mesa/gallium 10 bit version. I 
think i'll submit rev 3 later today or tomorrow and maybe we'll need to 
sort this out then, what goes where. I'll compare with Mareks branch...

The current state of my series for AMD here is that radeon-kms + ati-ddx 
works nicely under exa (and with a slightly patched weston), but the 
ati-ddx also needed some small patches which i have to send out. On 
amdgpu-kms i know it works under my patched weston branch.

What is completely missing is glamor support, ergo support for at least 
amdgpu-ddx and modesetting-ddx -- and xwayland.

>> For AMD, I applied Mario's patches (except Wayland - that didn't
>> apply) and added initial Gallium support:
>> https://cgit.freedesktop.org/~mareko/mesa/log/?h=10bit
>>
>> What's the status of Glamor?
>>
>> Do we have patches for xf86-video-amdgpu? The closed should have
>> 10-bit support, meaning we should have DDX patches already somewhere,
>> right?

Somewhere there must be some, as the amdgpu-pro driver with the 
proprietary libGL supported depth 30 at least in some version i tested 
earlier this year?

> 
> I'd like to test this out with nouveau as well... do I understand
> correctly that I shouldn't need anything special to check if it
> basically works? i.e. I apply the patches, start Xorg in bpp=30 mode,
> and then if glxgears works then I'm done? Is there a good way that I'm
> really in 30bpp mode as far as all the software is concerned? (I don't
> have a colorimeter or whatever fancy hw to *really* tell the
> difference, although I do have a "deep color" TV.) If used with a
> 24bpp display, is the hw supposed to dither somehow?x
> 
>    -ilia
> 

nouveau is quite a bit work to do and not so clear how to proceed.

My current series does do proper xrgb2101010 / argb2101010 rendering 
under gallium on both nv50 and nvc0 (Tested under GeForce 9600 for 
tesla, GTX 970 and 1050 for maxwell and pascal). I used PRIME render 
offload under both DRI3/Present and Wayland/Weston with both intel and 
amd as display gpus, so i know the drivers work together properly and 
nouveau-gallium renders correctly.

The display side for native scanout on Nvidia is somewhat broken atm.:

1. Since Linux 4.10 with the switch of nouveau-kms to atomic 
modesetting, using drmAddFB() with depth/bpp 30/32 maps to xrgb2101010 
format, but nouveau-kms doesn't support xrgb2101010, so setting Xorg to 
depth 30 will end in a server-abort with modesetting failure. nouveau 
before Linux 4.10 mapped 30/32 to xbgr2101010 which seems to be 
supported since nv50. If i boot with a < 4.10 kernel i get a picture at 
least on the old GeForce 9600 and GT330M.

If i hack nouveau-ddx to use a xrgb2101010 color channel mask (red in 
msb's, blue in lsbs) instead of the correct xbgr2101010 mask, then i can 
get nouveau-gallium to render 10 bits, but of course with swapped red 
and blue channels. Switching dithering on via xrandr allows to get 
rendered 10 bit images to get to a 8 bpc display, as confirmed via 
colorimeter. I hope a deep color TV might work without dithering.

According to

https://github.com/envytools/envytools/blob/master/rnndb/display/nv_evo.xml

gpu's since kepler gk104 support xrgb2101010 scanout. With a hacked 
nouveau-kms i can get the maxwell and pascal cards to accept 
xrgb2101010, but the display is beyond weird. So far i couldn't make 
much sense of the pixeltrash -- some of it remotely resembles a desktop, 
but something is going wrong badly. Also the xbgr2101010 mode doesn't 
work correct. The same is true for Wayland+Weston and even if i run 
Weston with pixman, keeping Mesa out of the picture. So nouveau-kms 
needs some work for all modern nvidia gpu's. Gamma table handling 
changed quite a bit, so maybe something is wrong there.

2. We might also need some work for exa on nvc0+, but it's not clear 
what problems are caused by kernel side, and what in exa.

3. In principle the clean solution for nouveau would be to upgrade the 
ddx to drmAddFB2 ioctl, and use xbgr2101010 scanout to support 
everything back to nv50+, but everything we have in X or Wayland is 
meant for xrgb2101010 not xbgr2101010. And we run into ambiguities of 
what, e.g., a depth 30 pixmap means in some extensions like 
glx_texture_form_pixmap. And the GLX extension generally seems to have 
unresolved problems with ARGB formats instead of ABGR formats, which is 
why Mesa doesn't expose ARGB by default -- only on Android atm.

So on nouveau everything except the gallium bits is quite a bit messy at 
the moment, but the gallium bits work according to my testing.

-mario