Re: ast: resolutions that require single-buffering (due to VRAM limitations) are unavailable

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



Thomas Zimmermann:
Hi

Am 25.10.22 um 09:12 schrieb Jeremy Rand:
Hi dri-devel,

I have two machines with ASPEED GPU's (ast Linux driver).  One machine is x86_64, running an ASRock Rack Tommy 90-SC02P1-00UBNZ GPU (AST2510 chipset) with KDE Plasma Wayland; the other is ppc64le, running an integrated AST2500 GPU with KDE Plasma X11.  Both the AST2510 and AST2500 have 16 MiB VRAM according to lspci.  Both ASPEED GPU's are advertised as supporting up to 1920x1200 resolution, but KDE only detects a maximum resolution of 1920x1080.

Some additional information about this bug can be found at https://forums.raptorcs.com/index.php/topic,31.0.html .

I believe this is a Linux bug, because it is solely dependent on the Linux version.  The following Linux versions are confirmed to have the bug:

Debian:
5.6.0-1 (ppc64el)
Fedora:
5.6.0-1.fc33.x86_64
5.6.0-1.fc33.ppc64le
5.17.5-300.fc36.x86_64
5.18.6-200.fc36.ppc64le
6.1.0-0.rc0.20221007git4c86114194e6.5.fc38.ppc64le

Whereas the following Linux versions are confirmed to work fine (max resolution detected by KDE is 1920x1200 as it should be, and that resolution works fine when selected):

Debian:
5.5.0-2 (ppc64el)
Fedora:
5.5.17-200.fc31.x86_64
5.5.17-200.fc31.ppc64le

I believe the bug was introduced by Linux commit 9253f830c9166bfa6cc07d5ed59e174e9d5ec6ca, which adds a VRAM size check that assumes double-buffering.  1920x1080 resolution at 4 bytes per pixel with 2 buffers is 16.6 MB, while bumping that to 1920x1200 results in 18.4 MB.  Since the VRAM size is 16 MiB == 16.8 MB, that explains the issue.

Thanks for reporting. It's been a known issue for a while.

But in the most recent devel tree, we have replaced ast memory management, so that it can now use the full vram size for scanout buffers. See


https://cgit.freedesktop.org/drm/drm-tip/commit/drivers/gpu/drm/ast/ast_mode.c?id=f2fa5a99ca81ce1056539e83c705f3d6bec62e31

To test, get the latest drm-tip from

   git://anongit.freedesktop.org/drm/drm-tip

and try on your machine.

The updated driver should become available in Linux v6.3.

Best regards
Thomas

Hi Thomas!

Thanks for pointing me to that branch. It took me some weeks to get it to build due to my lack of experience building kernels from source (hence the delayed reply), but I can confirm that the issue is fixed in drm-tip (1920x1200 works as it should on my ppc64le system; I didn't test on my x86_64 system). Additionally, drm-tip fixes a different AST bug that was causing certain Wayland ppc64le systems (mainly GNOME, KDE, and GDM) to hang on a black screen (for which I was halfway through preparing a bug report), so that is a pleasant surprise.

Looking forward to Linux v6.3.

Cheers,
--
-Jeremy Rand
Lead Application Engineer at Namecoin

Attachment: OpenPGP_signature
Description: OpenPGP digital signature


[Index of Archives]     [Linux DRI Users]     [Linux Intel Graphics]     [Linux USB Devel]     [Video for Linux]     [Linux Audio Users]     [Yosemite News]     [Linux Kernel]     [Linux SCSI]     [XFree86]     [Linux USB Devel]     [Video for Linux]     [Linux Audio Users]     [Linux Kernel]     [Linux SCSI]     [XFree86]
  Powered by Linux