Linux 5.14 To Bring SimpleDRM Driver, VC4 HDR, Marks More AGP Code As Legacy

[phoronix]

Phoronix: Linux 5.14 To Bring SimpleDRM Driver, VC4 HDR, Marks More AGP Code As Legacy

In addition to the initial batch of AMDGPU changes for Linux 5.14 that were mailed in on Thursday to DRM-Next, the initial DRM-Misc-Next pull also was sent off on its way to DRM-Next ahead of this next kernel cycle...

https://www.phoronix.com/scan.php?page=news_item&px=Linux-5.14-Initial-DRM-Misc

[jpegxguy]

NTFS pls

[MadeUpName]

Raspberry Pi has HDR? Last time I looked at one it barley had VGA due to lack of drivers. I thought Linux didn't support HDR yet?

[louis_irl]

Will this allow for flicker-free booting with AMD graphics?

[birdie]

Raspberry Pi has HDR? Last time I looked at one it barley had VGA due to lack of drivers. I thought Linux didn't support HDR yet?

10bit color per channel support under Linux is horrible to say at the very least. I now have such a monitor which works fine in Windows out of the box with 30bit color enabled, and in Linux I disabled deep color after ten minutes because half of my applications broke and became near completely unusable.

[illwieckz]

those still rocking out with a vintage AGP graphics card can keep on using new kernels.

Michael this is not true unfortunately.

AGP does not work for Radeon since end of 2020 on stock kernel with default configuration (starting with 5.9-rc1), the root cause seems to be bugs in Linux PCI code that were verified to be reproducible with PCIe and PCI GPUs in some situations.

AMD/ATI AGP cards stopped to work “on next reboot after an update” at the end of 2020, even on Ubuntu 20.04 LTS which backported in Linux 5.4 the AGP disablement code from Linux 5.9-rc1.

While disabling the AGP code it was expected those card would run in PCI mode, but the PCI fallback is not working: PCI GPUs look to be broken for years on AMD hosts running Linux, related bugs were verified even on Linux 4.4 (Ubuntu 16.04).

So to sum it up, starting with Linux 5.9-rc1 AGP Radeon cards are expected to run as PCI ones as a fallback, but the PCI code looks to be broken for more than 5 years.

• https://bugs.launchpad.net/bugs/1899304
  AGP disablement leaves GPUs without working alternative (PCI fallback is broken), makes very-capable ATI TeraScale GPUs unusable
• https://bugs.launchpad.net/bugs/1902981
  AGP GPUs driven as PCI ones (when AGP is disabled at kernel build time) are known to fail on AMD K8, K10 and Intel Kentsfield platforms
• https://bugs.launchpad.net/bugs/1902795
  PCI graphics broken on AMD K8/K10/Piledriver platform (while it works on Intel) verified from Linux 4.4 to 5.10-rc2
• https://lkml.org/lkml/2021/5/6/41
  On disabling AGP without working alternative (PCI and PCIe are also affected)

Interestingly, the related PCI GPU bug was reproduced from early AMD64 CPUs (K8) to AMD Piledriver platform (FX-9590), which is the platform before Ryzen (Ryzen is not tested).

That may be surprising, but AGP lived very lately, thanks to AMD who continued to produce AGP variants of their GPUs for a very long time. Here is an example of computer that is affected by the regression:

• MB Asrock AM2NF3-VSTA (AM2+ socket)
• CPU AMD Phenom II X4 970 (AM3 package, quad core, 3.5GHz)
• GPU HIS ATI Radeon HD 4670 IceQ (TeraScale RV730 XT, 1GB VRAM DDR3, OpenGL 3.3, HDMI)
• RAM 16 GB DDR2 800MHz (MB and CPU supports 1066MHz)

This Quad Core / 16GB of ram computer with capable GPU just did not rebooted properly after a minor update.

About that beefy AGP GPU, the chip is from 2008, and the card was still sold as new in 2012 and customers were still doing reviews for it in 2015. It even supported OpenCL 1.0 at the time (no driver on Linux today, though).

To compare with other open source GPU drivers mainlined in Linux, to outperform this AGP GPU in gaming performances an user has to get an Intel UHD 600 or an Nvidia GTX 1060 from 2016 (reference).

A temporary solution is to set radeon.agpmode to something that is not -1 on linux command line interface (values seems to be 0, 1, 2, 4 and 8), but better fix the underlying Linux PCI bugs anyway, because the uncovered bugs may also affect PCI and PCIe cards (both AMD/ATI and Nvidia) on some systems.

[smitty3268]

Raspberry Pi has HDR? Last time I looked at one it barley had VGA due to lack of drivers. I thought Linux didn't support HDR yet?

Linux supports it just fine. It's X and pretty much all of the various userspace applications that don't.

If you are running some kind of specialized program on the Pi that needs HDR you might be able to make it work though.