4k@120hz unavailable via HDMI 2.1
Brief summary of the problem:
I have a RX 6800 XT connected to a LG B9 TV via HDMI. As both these devices are HDMI 2.1, I should be able to send a 4k 120hz signal. However 120hz support is only available for 1440p resolution, and only 60hz is available for 4k. This is the case for both Wayland and Xorg.
Hardware description:
- CPU: AMD Ryzen 7 3700X
- GPU: RX 6800 XT (2f:00.0 VGA compatible controller [0300]: Advanced Micro Devices, Inc. [AMD/ATI] Device [1002:73bf] (rev c1))
- System Memory:
- Display(s): LG B9 55"
- Type of Display Connection: HDMI 2.1
System infomration:
- Distro name and Version: Arch Linux
- Kernel version: 5.10.2, 5.11-rc1 (I checked to see if this was fixed on 5.11rc1 (it isn't), but attached logs are for 5.10.2)
- AMD package version: No package
Attached files:
Activity
marked this issue as a duplicate of #1442
marked this issue as related to #1442
mentioned in issue #1442
HDMI 2.1 is not available on Linux due to the HDMI Forum. See: https://www.phoronix.com/scan.php?page=news_item&px=HDMI-Closed-Spec-Hurts-Open
I noticed that the newly released nvidia open source kernel driver has full support for HDMI FRL aka HDMI 2.1
Can you please implement this feature now?
@amd_user NVIDIA implementing it doesn't mean drm/amd can, FYI. Intel does it via proprietary firmware iirc, which does DisplayPort -> HDMI 2.1.
Edited by Dallas Strouse@roadapathy I really wish that happens soon. No idea how hard that would be to develop without official documentation.
I have the same issue with an RX 6800 graphics card and an LG C1 TV. I can transmit 4K @ 120Hz but it gets transmitted in YCbCr 4:2:0 (which is within HDMI 2.0 specs) instead of YCbCr 4:4:4 or RGB.
Could the AMDGPU driver be utilizing only TMDS and not the new FRL (Fixed Rate Link) transmission protocol required for the new HDMI 2.1 signals?
I can transmit 4K 10bit Full RGB @ 120hz on Windows with no problems.
Edited by Nuno PereiraThe just released Nvidia open source kernel driver supports HDMI 2.1 aka HDMI FRL
I hope this means we will finally get support in the AMD driver.
@agd5f How is Intel able to do this in their opensource driver? Would something similar be possible for AMD?
https://www.phoronix.com/news/Intel-HDMI-2.1-FRL-Linux
https://lists.freedesktop.org/archives/intel-gfx/2022-November/311389.html
Edited by Jaap Buurman
Anyone knows if this patch from November has anything to do with HDMI 2.1 Fixed Rate Link support?
Fixed Rate Link (FRL) is the feature that allows enough bandwidth to support 4K@120hz and such.
Somewhat off topic, but do you know if DP to HDMI 2.1 adapters are supposed to work on Linux+AMD now? I've got the Club3d CAC-1085 (which afaik is the only DP 1.4 to HDMI 2.1 adapter on the market) and it still only does 4k60 4:4:4 on Linux on Fedora 36 beta (with kernel 5.17 that contains that patch, a 6800xt, and an LG CX with a certified cable that does 4k120hz 10bit 4:4:4 on Windows).
I would be surprised if this would actually add FRL support for even just the Club3D adapter (I have one too). I believe this is one of the parts that is not allowed to be implemented by the HDMI forum in an open-source driver. Hence why NVIDIA and probably Intel will not add proper HDMI 2.1 support in Linux. Me and others shared a fair bit of critique on NVIDIA for not adding HDMI 2.1 support in their proprietary binary-only driver on Linux even though they are allowed to. I even bought an RTX 3700 just to give this a try.
For now I have given up on HDMI 2.1 / FRL support on Linux and will wait on the next iteration of graphics cards with DisplayPort 2.0 and possibly an adapter. Read about some already being developed and other than the DP 1.4 -> HDMI 2.1 adapter, DP 2.0 has a lot more bandwidth than HDMI 2.1 so I hope for a proper adapter this time.
@mdeboer Do you know if those adapters are generally latency free and if they do support VRR?
Edited by Nuno Pereira
Yeah I'm in much the same boat. Bought a 6800xt then afterwards bought a LG C1 HDMI2.1 screen to only discover this issue. ATM Linux will default support back to CYB420 which is HDMI2.0 mode of poorer quality then RGB. If you force RGB mode it can only do 4k@60hz instead of 120hz as desired.
I know some HDMI2.1 code has landed in the NVIDIA open-source drivers somehow; not sure what will happen with that. Either HDMI2.1 forum license guys change it to allow open-source support or they sue NVIDIA (which would be entertaining for sure)
HDMI2.1 needs to support use in Open-Source drivers!!!
Depending on what happens, my next GPU will likely be a RTX4080 (if HDMI2.1 gets support) as I don't want to deal with this crap no more!
PS. I've tried DP to HDMI2.1 adapters and it only gets you 4k@60hz RGB modes; IF they even work at all!!!
Edited by Jarrard Loweits not optimal in any way or shape .... but i got the club3d dp1.4 to hdmi adapter, and my 6700xt and LG C1 seem to behave better ... i can get 120hz rgb444 ... no VRR and the amd memclk is always max ...but text looks sharper ... way way better looking chroma subsampling test image now.... i still hope amd finds a way to enable hdmi2.1 support .....
mentioned in issue #2058 (closed)
I can confirm that with the latest 1.07 firmware, the Club3d CAC-1085 works on linux at 4k120hz 4:4:4 with a 6800xt. You need to contact Club3d's support to get the new firmware, and you'll have to use Windows to update the firmware, but it does finally work now (at least, it worked for me on Fedora with kernel 5.18.something).
Oh my bad, I read it wrong. I thought his graphics card had gotten a firmware update that implemented the closed part of HDMI 2.1.
There is no HDMI2.1 for AMD open-source drivers, and likely never will be.
Neither for Intel. But it's a bit hard to believe that the both Intel and AMD will drop support for future HDMI versions and won't coerce the HDMI forum to allow at least the FRL mode. Together they are by far the largest share of PC HDMI vendors.
all i know is that i got sick of tinkering and while i did get 4k120hz in rgb444 with the adapter ... i kept having moments where it will dump lots of kernel errors and I'll have to reboot .... so ...i got a rtx3070 ... 4k120hz rgb444 was what it did by default ..with vrr enabled and working ... it took about 1/1000 of the time i spend to get my 6700xt to sort of work ... i guess I'm giving up on amd gpus for now ... if nvidia can make hdmi2.1 work ...in their open source driver ... AMD can surely find a way
no clue - i compiled this: https://github.com/NVIDIA/open-gpu-kernel-modules/ .... it is very likely that they have a huge binary blob in there ... but how does that change anything ? One driver worked and the other did not... on top of that all my resume from sleep issues went away ... and that is after i spend what feels like years making my 5700xt and then 6700xt work. I want to use amd cards, hence all the effort i put and i know that the eng team does all that they can and are more than capable, but at the end it did not work even after paying premium (more $ than nvidia and way more time spend). just fyi - i had rgb444 issues with my old-er displayport monitor too ... had to spend hours messing with custom edid and kernel patches, so its not just the hdmi2.1 issue.
You're using the Nvidia closed-source driver. Nvidia has no open-source driver available for the end-user.
@nfp0 this is actually completely wrong. @gyordanov even provided you with a direct link.
Here's a link to the Phoronix article back when NVIDIA first released their fully FOSS GPU kernel driver: https://www.phoronix.com/review/nvidia-open-kernel.
The very first line of that article:
The day has finally come: NVIDIA IS PUBLISHING THEIR LINUX GPU KERNEL MODULES AS OPEN-SOURCE! To much excitement and a sign of the times, the embargo has just expired on this super-exciting milestone that many of us have been hoping to see for many years.
NVIDIA now provide both an open and closed kernel driver. Their userspace drivers remain closed source, but those are irrelevant, because the kernel driver(s) are what handle HDMI support. No, no one here is referring to Nouveau. These are official, Nvidia kernel drivers. And as several people have pointed out, the OPEN NVIDIA GPU Kernel driver seems to support HDMI 2.1. @amd_user literally posted a direct link to the very line in the code.
@nfp0 this is actually completely wrong. @gyordanov even provided you with a direct link.
I'm happy to be wrong about this, but @gyordanov's link was posted after my post, not before.
And as several people have pointed out, the OPEN NVIDIA GPU Kernel driver seems to support HDMI 2.1
If the FRL functionality is really implemented in open-source then I'm glad that's the case!
But that begs the question:
Why were AMD and Intel forbidden from doing such but not Nvidia?
@agd5f can a vendor implement FreeSync on top of HDMI 2.1 so that it works with amdgpu? I'm asking because I just connected my Samsung TV (GQ75Q70AATXZG) with my 6800 XT and both 4k 120Hz and FreeSync somehow work fine...
Could you be doing 4k 120Hz at HDMI 2.0 bandwidth using chroma subsampling? Since it's a bandwidth problem, reducing color information lets the system do higher refresh rate with the same bandwidth.
Additionally, I've found Wayland will typically automatically do this if asked to do an impossible bandwidth. In Gnome on Wayland for example, you just configure it to use the higher refresh rate and it automatically switches to 1:2:4 chroma subsampling without saying anything about it.
To test, view this image on the monitor/TV (image shouldn't be zoomed in at all): https://www.rtings.com/images/test-materials/2017/chroma-444.png
The text is all equally clear with no chroma subsampling, but some of the text can get very jumbled if it is enabled.
For FreeSync - I believe FreeSync is just straight up supported on HDMI 2.0. It doesn't use the dedicated VRR protocol, but it's existed and worked on HDMI since before that existed.
Edited by David RossSome of the text does look fuzzy. What confuses me about it is that I just tested the HDMI 2.0 ports on the TV and with those I only get 60Hz ¯\_(ツ)_/¯
Additionally, I've found Wayland will typically automatically do this if asked to do an impossible bandwidth
The compositor has no influence over that yet. The driver does that - if you use the modesetting driver on Xorg, it should do the same.
What confuses me about it is that I just tested the HDMI 2.0 ports on the TV and with those I only get 60Hz
@Zamundaaa Your TV most likely has a different EDID for the HDMI 2.1 and 2.0 ports. The 2.0 ports probably don't advertise any 120hz capability.
And yeah, if the text looks fuzzy, you're probably outputting YCbCr with chroma subsampling, which is another issue in itself, discussed here: #476
You can force RGB by editing your EDID and removing the YCbCr capability, but you won't be able to do 120hz. But!! You might want to take a look at this: #1417 (comment 1552622)
It looks like someone over at the Level1Tech forums managed to output 4K@120hz RGB from his RX 6000 card!
https://forum.level1techs.com/t/4k-120hz-hdmi-2-1-amd-6000-series-omg/168664/4Can anyone here explain what he's doing exactly? Is he going out of spec? Do those code changes perhaps trigger the card's firmware to change to FRL instead of TMDS? The TV states he is in TMDS mode though.
mentioned in issue #476
Now even Intel is implementing HDMI FRL in their kernel driver:
https://www.phoronix.com/news/Intel-HDMI-2.1-FRL-Linux
https://lists.freedesktop.org/archives/intel-gfx/2022-November/311389.html
-
Current Intel Arc Graphics (DG2/Alchemist) only natively support HDMI 2.0 but HDMI 2.1 can be an option with some of the cards where the board vendor chooses to use a PCON for converting a DisplayPort 2.0 output from the GPU to an HDMI 2.1 interface. But now for Meteor Lake integrated graphics (and presumably for DG3/Battlemage) there will be native HDMI 2.1.
So probably proprietary firmware, I doubt it'll work for DG3 though since it'll be native 2.1.
Edited by Dallas Strouse -
@nfp0 only the HDMI forum making 2.1 not able to be implemented in an open source driver.
If the 6000 cards don't do native HDMI 2.1 it could be done, but otherwise your best chance is a DP -> HDMI adapter.
There is 1 company that has or is making a DP2.0 to HDMI 2.1 adapter with VRR and HDR but I forgot their name. They are using a NEW chip to do it so supply is probably awful. I wouldn't be surprised if the adapter costs $100 or more.
There was a few articles about it I found via Google Search. Never followed up on it as that was while ago.
Could be that PS196 thing... but again, I don't see anyone selling anything. Must be quite an exclusive item to get your hands on. Also you need a DP2.0 card afaik....
Edited by Jarrard LoweWell if your display setting is below 32.4Gbps (DP1.4 max) it should be fine. But these new adapters may not quite function that way, won't know until they become available.
Edited by Jarrard LoweIs this the adapter you are referring to? Hopefully it makes it into a commercial product soon... I would love to have this for my RX 7900 XTX
would this be an option to use with the 7900 xtx?
@Riddick My intention would be to use 4K@120hz on my TV, which my card (RX 6800) is advertised as supporting.
So no, that is not enough.EDIT: Nevermind. The bandwidth would be enough.
Edited by Nuno Pereiratwo things:
First, none of us are AMD, so I don't think that's super relevant.
Second, though, why wouldn't that work for 4k 120hz? DisplayPort 1.4 fully support 4k 120hz, even without DSC. As long as you have a connector that car convert DP 1.4 to HDMI of equivalent bandwidth, 4k 120hz is definitely possible.
DP 1.4 can even do 4k 144hz if using DSC (which is a lossless compression).
DP 2.0 is only needed if you're going for 8k 144hz.
@nfp0 Yeah same boat. Basically if you have Intel or NVIDIA card you get HDMI2.1 no problem.
If we run the display it pushes it to 4:2:0 as we all know in order to achieve 120hz at 4k setting on AMD.
I have not been using Linux for a while mainly for this reason. I do intend to buy a 4090 at some point and be done with all the issues, but who knows how bad 2023, maybe all stock will go poof, maybe prices will triple... anything goes at this point.
@daboross I was under the impression AMD reads these issues here. Am I wrong?
And yeah, you're right. DP 1.4 is enough for 4K@120hz at 8bpc. I was checking the Wikipedia table for HDR (10bpc). Then an adapter would mostly work. But I don't know any that supports VRR.
@Riddick I'll email AMD support complaining. Do the same. The more the merrier. They should not advertise this feature if they can't fully support it.
@nfp0 Have you tried their AMD PRO driver suite off the website? does it have working HDMI2.1?
I've only tried the Encoder/Vulkan component of it not the full driver itself.
Here we are all talking about the lack of support for HDMI2.1 in MESA drivers which isn't the only option.Basically if AMD supports HDMI2.1 in their closed or own drivers via their website then they technically are giving support.
But I've been so long out of the loop with their own drivers that I have no idea if AMDGPU-PRO or whatever it is on their website supports 2.1 (NOT amdvlk driver, that is separate thing).
UPDATE: I checked, looks like there may not be a option since AMDGPU-PRO works on top of Kernel driver which is open-source. So your right AMD provides no method for HDMI2.1 under Linux which is EXTREMELY BAD! They need to change all their advertisement to say HDMI2.1 (Windows ONLY).
Edited by Jarrard Lowe@ironashram That looks promising as it does indeed use the PS196. It is usb-c however, and therefore only DP 1.4
Would probably work if I could confirm that it supports VRR...
I guess we'll have to wait for a while. Until HDR is supported on Linux I don't really need a solution to this issue. Hopefully AMD has fixed this by then, or a generally available adapter exists.
@bernharl It should as its using USB-C DP1.4 Alt-Mode. But what color options do you get at 4k 120hz is the question, is it 8bit 444 or 10bit 444, what about HDR enabled at same time?
Lots of questions and unfortunately often you don't truly know until somebody technical buys one and tries it.
@Riddick Yeah, I believe some other people in this thread also confirmed not even AMDGPU-PRO supports HDMI 2.1.
They need to change all their advertisement to say HDMI2.1 (Windows ONLY)
Completely agree! I bought this card exclusively on the premise of using 4K@120hz through HDMI.
DP -> HDMI adapter I would buy one in a heartbeat if I can find one that supports VRR. Anyone knows one?
@nfp0 I don't think it's possible to support VRR easily with DP -> HDMI2.1 because VESA adaptive sync (used by DP) is a different protocol to HDMI 2.1 VRR (and freesync over HDMI is different again).
The adapter itself would need to convert it, and that would add complexity/cost. Hopefully the Paradetech chip does became a real thing, although I suspect it will indeed be quite expensive.
It should as its using USB-C DP1.4 Alt-Mode. But what color options do you get at 4k 120hz is the question, is it 8bit 444 or 10bit 444, what about HDR enabled at same time?
I've only tested on Windows so far but this adapter supports everything but VRR (4k@120hz, 10-bit 4:4:4, and HDR) although I had to force enable 10-bit for HDR when normally it would enable it on it's own.
Edited by aqxa1As someone already said, there is no such thing as a proprietary AMD GPU kernel driver. The PRO drivers only contain proprietary USERSPACE (OpenGL, Vulkan, OpenCl) components. It still uses the FOSS
amdgpukernel driver.The kernel driver is what handles all resolution/refresh rate/display protocol stuff. There is no workaround.
So your right AMD provides no method for HDMI2.1 under Linux which is EXTREMELY BAD! They need to change all their advertisement to say HDMI2.1 (Windows ONLY).
@Riddick They really don't, though. Every single retail page for every single GPU, motherboard, CPU, etc use "PC = Windows." Even though that's not actually true, it doesn't matter because the overwhelming consensus is that PC = Windows. Linux is never mentioned, except VERY rarely.
Go look at the official web page for your motherboard. Look at the specs and see what OS it says it supports. I almost guarantee it will only say Windows 10/11 (or just Windows). I've never owned a motherboard that has its webpage mention Linux. That's just the way things are.
@gardotd426 I'm sorry, but Linux is specified in AMD's official website:
Together with this:
There should at least be a note saying HDMI 2.1 is not available on the Linux drivers.
@daboross I was under the impression AMD reads these issues here. Am I wrong?
It's a bit late, but I wanted to say: you're right. I was wrong here, and under the wrong impression about this repository and its issues.
The fact that this is explicitly the place for community feedback to AMD makes it even more puzzling that, as far as I can tell, no one from the AMD team has acknowledged nor commented on any way to fix this.
no one from the AMD team has acknowledged nor commented on any way to fix this
@daboross Indeed. I guess the only way to reach them is through this: https://www.amd.com/en/support/contact-email-form
I've already sent my complaint.
no one from the AMD team has acknowledged nor commented on any way to fix this.
@daboross there isn't any way currently for the user to fix this. And the only open driver that supports HDMI 2.1 uses a hardware-level DP -> HDMI converter, so it might not be possible unless a firmware only implementation is legally and technically viable.
Nevertheless, I agree that this issue tracker seems to only be monitored sporadically which is unfortunate. You might try asking on Phoronix as there are a few people from AMD that hang out there. Or try on /r/AMD.
Edited by aqxa1the only open driver that supports HDMI 2.1 uses a hardware-level DP -> HDMI converter
@aqxa1 Is this what both Nvidia and Intel are using?
there isn't any way currently for the user to fix this.
Right, yeah - I mean them commenting on if/when they can fix it.
firmware only implementation is legally and technically viable.
This is the route I'd expect if they do fix it. Nvidia does this, in my understanding, though to a much greater extent - their current official open source driver delegates nearly everything to firmware.
I don't know if Nvidia also has a hardware DP->HDMI converter, but if they don't, then I would expect that's a good proof for the legality of the firmware approach? Only question is how easy it is to integrate that into AMD's driver structure and if whatever runs their firmware blobs is powerful enough to do that.
Edited by David Ross@nfp0 I don't have a nvidia gpu to test but it appears the open kernel drivers are not the default and don't support all features (including G-Sync). See here:
However, in the current release, some display and graphics features (notably: G-SYNC and SLI), as well as power management, and NVIDIA virtual GPU (vGPU), are not yet supported.
So it's hard to say whether they actually support HDMI 2.1, particularly if users are actually using the prop. stack when they think they are using the open one. Users with Nvidia cards would need the follow the instructions above, as well as having a recent enough GPU, access to HDMI 2.1 display, and ability to verify it's using 4:4:4 and not chroma subsampling.
@nfp0 AMD's code also has references to FRL from a quick grep, although it's not clear if it's only for DP -> HDMI without reading more deeply. More references are in recent DCN so maybe that's an indicator of recent/future support (I'm not sure what gen DCN31 maps to). There's also some recent commits in the staging kernel indicating support for Freesync over PCON (DP -> HDMI converter presumably) which is interesting.
Anyway, that looks like some kind of support for Nvidia. I'd like to see confirmation of it actually working but I'll assume it's working for now.
Edited by aqxa1@aqxa1 Yeah, I believe that is the same we were discussing here: #1417 (comment 1202634)
But there is hope that this is for an internal DP -> HDMI converter built into the card! The same way Intel is supporting FRL, it seems.
I have a 6800XT and tried a Cruxtec DP1.4-> HDMI 2.1 Cable which uses the PS196 chip. It Did not work with the LG G2 Monitor for me and produces garbage
( https://www.pbtech.co.nz/product/CABCXT10301/Cruxtec-2m-Displayport-14-to-HDMI-21-Cable----8K60 )Fedora38 (6.3.x kernel series)
Just a quick update for those desperate to resolve the subchroma issue 4k@120. I can confirm that after several different approaches to try and work around this (including using an ARC/Nvidia card as a scanout card with the RDNA rendering; with limited success, and a direct 8K Displayport->HDMI2.1 cable as pictured above) the working combination I have is to use the motherboard displayport in from the RDNA2/3 output, and a Thunderbolt4/USBC DP Alt mode adaptor. - This one specifically https://www.amazon.com.au/dp/B08MSWMXT4?ref_=pe_19115062_429603572_302_E_DDE_dt_1
I was surprised that out of the box even VRR and Freesync premium syncs and works via this pathway. Which I am guessing is a by product of the DP in on the motherboard (Asus Proart X570) as other reviewers have stated they cannot use VRR with the same adaptor.
Technically they can just support freesync which should be same on both DP and HDMI2.1
My understanding is that they are not the same, but I've found scant documentation on the protocol(s). Probably just looking at the source code would be the simplest way. You'd also think that freesync over DP -> HDMI2.1 would just work if the protocols were the same, but I could be wrong. If they are different, I wonder if a non-standard DP output could be sent from the source, using freesync-over-hdmi instead of freesync-over-dp.
As an aside, it seems that Intel's new GPUs don't actually support HDMI 2.1 through firmware, but through a dedicated DP1.4 -> HDMI2.1 chip. I've seen mixed views as to whether VRR/freesync actually works on those cards but if so, it would indicate it's possible and hopefully we get converters in the future (as well as being included on new AMD GPUs to sidestep this nonsense).
Edited by aqxa1
