Comments (51)
As i think more Data is better i also want to contribute some dumps. I have the Samsung Odyssey G9 (LC49G95T) and i can also get DDC running with HDMI but not DisplayPort. The Problem is i can only provide mixed Data with the HDMI being connected to my Intel Notebook and the DisplayPort being connected to my Vega running with the amdgpu driver.
The files are labeled Intel-interrogation and Intel-env for the HDMI on my Notebook and AMD-interrogation and AMD-env for DisplayPort on my VEGA.
Intel-env.txt
Intel-interrogate.txt
AMD-interrogate.txt
AMD-env.txt
Output from "i2cdetect 4" on the AMD System: i2cdetect.txt
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i contacted samsung chat support (i know), and they told me that the monitor currently doesn't support ddc/ci over dp. looking at the ddc protocol (wikipedia entry, i know.. :), it seems that ddc/ci is optional over dp:
Like modern analog VGA connectors, the DVI and DP connectors include pins for the display data channel (DDC), but DP supports DDC within its optional Dual-Mode DP (DP++) feature in DVI/HDMI mode only.
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I've not directly swapped the monitors due to a short DVI cable, but the problem stays with the DP connection (same cable, never had problems with it)
If I attach the previous DVI-Monitor via DP, its manufacture year and EDID-version changes (2014->2013; 1.3->1.4) (I have rebooted the system to verify it)
I have no idea, how to enable DDC/CI in the OSD or if it can be disabled.
Also the EDID information for the DP monitor do not show up every time (see both attached files)
ddcenv.txt
ddcenv2.txt
please tell me, if I can provide further information.
Edit:
The problem also exists under Windows 8.1 with the ScreenBright tool
And the problem also exists if I attach the DP monitor to the integrated Intel i915 card (Sandy Bridge)
I begin to think that there is a problem with the monitor itself and not with the video card.
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I have a similar problem here with an secondary Acer XB270HU on DP (only has that as connectivity). Manual states DDC2B support, works great on Windows but on linux no EDID and no DDC. Primary screen (Samsung SA850, also over DP) works great, even with DDC controls for brightness etc.
When plugging in the Acer:
Aug 05 00:28:44 believe kernel: [drm:amdgpu_atombios_encoder_set_bios_scratch_regs] DFP2 connected
Aug 05 00:28:44 believe kernel: [drm:drm_dp_i2c_do_msg] I2C nack (result=0, size=0
Aug 05 00:28:44 believe kernel: [drm:drm_dp_i2c_do_msg] I2C nack (result=0, size=0
Aug 05 00:28:44 believe kernel: [drm:drm_dp_i2c_do_msg] I2C nack (result=0, size=0
Aug 05 00:28:44 believe kernel: [drm:drm_dp_i2c_do_msg] I2C nack (result=0, size=0
Aug 05 00:28:44 believe kernel: [drm:drm_dp_i2c_do_msg] I2C nack (result=0, size=0
Aug 05 00:28:44 believe kernel: [drm:drm_dp_i2c_do_msg] I2C nack (result=0, size=0
Aug 05 00:28:44 believe kernel: [drm:drm_dp_i2c_do_msg] I2C nack (result=0, size=0
Aug 05 00:28:44 believe kernel: [drm:drm_dp_i2c_do_msg] I2C nack (result=0, size=0
Aug 05 00:28:44 believe kernel: [drm:drm_dp_i2c_do_msg] I2C nack (result=0, size=0
Aug 05 00:28:44 believe kernel: [drm:drm_dp_i2c_do_msg] I2C nack (result=0, size=0
Aug 05 00:28:44 believe kernel: [drm:drm_helper_probe_single_connector_modes] [CONNECTOR:49:DP-2] probed modes :
Aug 05 00:28:44 believe kernel: [drm:drm_mode_debug_printmodeline] Modeline 82:"1024x768" 60 65000 1024 1048 1184 1344 768 771 777 806 0x40 0xa
Aug 05 00:28:44 believe kernel: [drm:drm_mode_debug_printmodeline] Modeline 79:"800x600" 60 40000 800 840 968 1056 600 601 605 628 0x40 0x5
Aug 05 00:28:44 believe kernel: [drm:drm_mode_debug_printmodeline] Modeline 78:"800x600" 56 36000 800 824 896 1024 600 601 603 625 0x40 0x5
Aug 05 00:28:44 believe kernel: [drm:drm_mode_debug_printmodeline] Modeline 80:"848x480" 60 33750 848 864 976 1088 480 486 494 517 0x40 0x5
Aug 05 00:28:44 believe kernel: [drm:drm_mode_debug_printmodeline] Modeline 77:"640x480" 60 25175 640 656 752 800 480 490 492 525 0x40 0xa
I2C nack
doesn't seem right. ddcutil returns: Failure getting EDID for /dev/i2c-9: status code=EREMOTEIO(-121): Remote I/O error
but that makes sense if the kernel isn't able to set up I2C comms properly.
i2cdetect:
0 1 2 3 4 5 6 7 8 9 a b c d e f
00: -- -- -- -- -- -- -- -- -- -- -- -- --
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
50: 50 -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
70: -- -- -- -- -- -- -- --
Since it works fine on Windows 10 with the GTX980, I will take a stab at booting a livecd on it and see where that gets me. I can also try the onboard i915 with it, have done neither yet.
Edit: fwiw this is with 4.12.4 and amdgpu on a HD7850
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So here's the same monitor on a GTX980, Ubuntu 17.04 live:
Display 1
I2C bus: /dev/i2c-16
Supports DDC: true
EDID synopsis:
Mfg id: ACR
Model: XB270HU
Serial number: #ASOQgqYB8LDd
Model year : 2013
EDID version: 1.4
VCP version: 2.2
Invalid display
I2C bus: /dev/i2c-19
Supports DDC: false
EDID synopsis:
Mfg id: ACR
Model: XB270HU
Serial number: #ASOQgqYB8LDd
Model year : 2013
EDID version: 1.4
DDC communication failed
Clearly there is an EDID here since it's detected when plugged in this GTX980. And I even have ddccontrol working on i2c-16, which is nvkm-0000:01:00.0-aux-0009 I2C adapter
- so clearly it's an issue with the aux code. e.g. ddcutil setvcp -b 16 10 50
sets brightness levels.
ddcutil env for the box with a gtx980 - acer on i2c-16 here as only monitor
ddcutil env for the box with a HD7850 - acer on i2c-9 here as second monitor, primary on i2c-8
So it's a mystery to me why it's not working on the radeon card; perhaps because this is a G-SYNC monitor and it's doing something non-standard?
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I assume you are reading the comments over email since I fixed the link shortly after commenting; in any case, attached the data through Github this time. I included an interrogate as well.
hd7850-card-i2c.txt
hd7850-detect.txt
hd7850-env.txt
hd7850-interrogate.txt
gtx980-interrogate.txt
gtx980-find-i2c.txt
gtx980-env.txt
gtx980-detect.txt
Note that these are 2 different machines with the same CPU model; the HD7850 machine is the dual monitor setup with Debian 9 and the GTX980 is windows box where I just use a Ubuntu 17.04 live boot.
I tested this also with just the Acer screen attached and with different DP cables but none of that had any effect. I am yet to try connecting the Acer to the onboard Intel DP.
Also, on the gtx980 with the Ubuntu live cd, there is no /sys/class/drm/card*/card*/i2c*; it looks almost as if all i2c devices are under the nouveau driver. I've attached a find /sys|grep i2c instead though can't say how useful that is; this may or may not be a kernel issue.
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No particular reason for amdgpu, but the radeon driver yields the exact same thing. I've attached a new set of files with radeon driver; in this set you'll see that I turned on drm debugging, then unplugged and inserted the Acer. Look for 'I2C nack'.
hd7850-card-i2c-radeon.txt
hd7850-interrogate-radeon.txt
hd7850-env-radeon.txt
hd7850-detect-radeon.txt
So it's pretty obviously an issue with both radeon and amdgpu failing to properly init the monitors I2C. I will try the screen on the Intel iGPU next.
Since it's clearly a kernel issue, do you know the best place to address this further? dri-users seems to be a dead list.
Thanks!
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The monitor does DDC/CI - it's enabled and cannot be turned off in the OSD. I've also attached it to intel iGPU, same problem (see interrogate). Also attached SoftMMCS report and log.
intel-card-i2c.txt
intel-interrogate.txt
softMCCS.txt
ACR0408 softMCCS test report.txt
Since it happens with both Intel and Radeon/AMDGPU I guess I can try to work with intel-gfx team; if you have any further suggestions I'm all ears. Thanks :)
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Any news on this? I'm experiencing similar problems.
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I've gotten nowhere. Made a bugzilla bug for the intel-gfx team here: https://bugs.freedesktop.org/show_bug.cgi?id=102069 - I suggest to add to that thread if you get the bug on intel GPUs but not amd/nvidia gpus.
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Yes, I'm using the i915 driver. However by now I've managed to get it to work, by using a display port to DVI adapter cable. I'm trying to switch inputs and the associated command does not support switching to DP input. This leads me to the suspicion that maybe the monitor itself is part of the problem. Still investigating.
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Nope, I'm not Gerben Meijer. Yes, it does support x60. That is exactly the feature I'm trying to use. However while the monitor has a D-SUB (VGA), DP and DVI Input ddutil lists these values when probing:
Feature: 60 (Input Source)
Values:
01: VGA-1
03: DVI-1
04: DVI-2
None of these values support switching to the DP input and funnily the monitor doesn't even have a secondary DVI input. So I'm guessing the firmware is screwed up or something...
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Hello, I am using a radeon gpu and a DDC CI capable monitor (mitsubishi RDT232WLM).
Unfortunately the test result is also "Invalid display" and "DDC communication failed".
Posting the output of ddcutil environment --verbose and ddcutil detect --verbose:
detect.txt
environment.txt
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from ddcutil.
I assume you're the same person as user magnesium who posted a similar
query in AUR (https://aur.archlinux.org/packages/ddcutil/).
Yes, I am the same person.
You're running a version of ddcutil (0.8.6) that's over a year old. The
current version, 0.9.5, is in AUR. If you're actually using ddcutil, I
suggest you upgrade.
Upgrade done.
You might also try using a different connector, though the
specifications I've found, as well as the environment output, indicate
there's no DisplayPort connector on this monitor and DisplayPort is the
one connector that tends to show variation.
This monitor and video card does not have Displayport, but tried switching conectors from HDMI to old DVI and... it worked!
Now, the monitor is detected!! Success!!!
Seems the problems is with HDMI connector!
@rockowitz Thank you very much!!! Live long to ddcutil.
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In terms of circuitry, DVI and HDMI are essentially
the same.
I didn't know that.
What connectors were you using on the video card in each case?
I'm using the same connectors on monitor and video card side. HDMI with HDMI, and DVI with DVI. No adapters of any kind.
Connecting both HDMI and DVI (but using DVI of course), the funcion loadvcp (profile) does not work.
[ia@sun ~] % sudo ddcutil loadvcp ddcnight [1][8:59:34]
Monitor not connected: RDT232WLM - 0Z247468AJ
So I have to disconnect HDMI permanently to use loadvcp.
Can I ask you run the interrogate command and send the output?
Of course.
interrogateHDMIandDVI.txt
interrogateDVIonly.txt
interrogateHDMIonly.txt
Hoping this could help others. Thank you for your attention.
(Addendum)
For the first time, I noted that OSD configurations for each connection is saved in a separate buffer, inside the monitor. Setting brightness and color for DVI does not interfere with HDMI saved config and vice versa. Perhaps could this be a clue.
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You ran the interrogate command as user ia, not root, so lacked
privileges to access the /dev/i2c devices. Please run it as root.
Here we go:
ROOTinterrogateDVI.txt
ROOTinterrogateHDMI.txt
ROOTinterrogateHDMI+DVI.txt
Alternatively, you can create group i2c, assign the /dev/i2c devices to
that group, grant RW access to the dev/i2c devices to members of that
group, and assign user ia to the group. See the comments at the end of
the (current) interrogate output, or page Device Permissions
I'll study about this and learn later
Best Regards.
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I have a similar issue as this, except for I am using (having trouble with) HDMI. My monitor is an ASUS VG248QE, DDC enabled in the OSD. It is also connected to a Windows 10 machine through an Nvidia GTX 780 GPU using Display Port, and DDC works there. However on Linux I am using Integrated AMD Vega Graphics with the amdgpu
driver. More specifically the Ryzen 2400G, which uses Vega 11 graphics. Motherboard is a MSI Gaming Carbon Pro.
I'm using 0.9.5-1 of ddcutil on Arch Linux with the 5.0.5 Linux Kernel.
$> ddcutil detect --verbose
Output level: Verbose
Reporting DDC data errors: false
Trace groups active: none
Traced functions: none
Traced files: none
Force I2C slave address: false
User defined features: disabled
Invalid display
I2C bus: /dev/i2c-4
I2C address 0x50 (EDID) present: true
Is eDP device: false
/sys/bus/i2c/devices/i2c-4/name: AMDGPU DM i2c hw bus 0
EDID synopsis:
Mfg id: ACI
Model: VG248
Serial number: FALMQS138687
Manufacture year: 2015
EDID version: 1.3
Product code: 9381
Extra descriptor: Unspecified
Video input definition: 0x80 - Digital Input
Supported features:
DPMS standby
DPMS suspend
DPMS active-off
Digital display type: RGB 4:4:4
Standard sRGB color space: False
White x,y: 0.313, 0.329
Red x,y: 0.650, 0.329
Green x,y: 0.331, 0.622
Blue x,y: 0.151, 0.053
Extension blocks: 1
EDID source:
EDID hex dump:
+0 +4 +8 +c 0 4 8 c
+0000 00 ff ff ff ff ff ff 00 04 69 a5 24 01 01 01 01 .........i.$....
+0010 2c 19 01 03 80 35 1e 78 ea 9d e5 a6 54 54 9f 26 ,....5.x....TT.&
+0020 0d 50 54 b7 ef 00 71 4f 81 80 81 40 81 c0 81 00 .PT...qO...@....
+0030 95 00 b3 00 01 01 02 3a 80 18 71 38 2d 40 58 2c .......:..q8-@X,
+0040 45 00 13 2b 21 00 00 1e 00 00 00 fd 00 32 4c 1e E..+!........2L.
+0050 53 11 00 0a 20 20 20 20 20 20 00 00 00 fc 00 56 S... .....V
+0060 47 32 34 38 0a 20 20 20 20 20 20 20 00 00 00 ff G248. ....
+0070 00 46 41 4c 4d 51 53 31 33 38 36 38 37 0a 01 ad .FALMQS138687...
DDC communication failed
Is DDC/CI enabled in the monitor's on-screen display?
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sudo ddcutil env --verbose and sudo ddcutil interrogate
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from ddcutil.
Yeah I also have a second monitor attached (only) to the Vega GPU, it's basically an unbranded DVI monitor from PC World I believe, would be very surprised if it supported DDC.
Yes I am running Windows 10 in a virtual machine with my GTX 780 Ti (missed the Ti bit out before) passed through to it. DDC doesn't work at all on the Linux side ever, it is only on the DisplayPort connection on the VG248QE with it connected to the Windows VM that DDC works.
How are you switching from Windows to Linux and vice versa?
Peripheral wise just passing them through Libvirt. Monitor wise currently just changing the input source from HDMI to DisplayPort.
$> i2cdetect 6 # X19W
0 1 2 3 4 5 6 7 8 9 a b c d e f
00: 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f
10: 10 11 12 13 14 15 16 17 18 19 1a 1b 1c 1d 1e 1f
20: 20 21 22 23 24 25 26 27 28 29 2a 2b 2c 2d 2e 2f
30: -- -- -- -- -- -- -- -- 38 39 3a 3b 3c 3d 3e 3f
40: 40 41 42 43 44 45 46 47 48 49 4a 4b 4c 4d 4e 4f
50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
60: 60 61 62 63 64 65 66 67 68 69 6a 6b 6c 6d 6e 6f
70: 70 71 72 73 74 75 76 77
$> i2cdetect 4 # VG248QE
0 1 2 3 4 5 6 7 8 9 a b c d e f
00: -- -- -- -- -- -- -- -- -- -- -- -- --
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
30: -- -- -- -- -- -- -- 37 -- -- 3a 3b -- -- -- --
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
50: 50 -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
70: -- -- -- -- -- -- -- --
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i am also running amdgpu (an r9 280x) and a samsung odyssey g9 over dp. i'm also unable to get ddcutil to correctly address the samsung monitor. do you need me to post the env and interrogate outputs from ddcutil?
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The problem seems to be, that the G9 does not support DDC over Displayport.
There is no option disable/enable DDC in the OSD and it works out of the box when being connected via HDMI, but not when being connected via Displayport.
Just verified, that this is still the case with the latest firmware update. :(
The "VESA standard monitor" is the G9, the others are connected via Displayport and a Displayport -> DVI adapter.
Detected monitors :
- Device: dev:/dev/i2c-4
DDC/CI supported: No
Monitor Name: VESA standard monitor
Input type: Digital- Device: dev:/dev/i2c-3
DDC/CI supported: Yes
Monitor Name: SyncMaster 245B
Input type: Digital
(Automatically selected)- Device: dev:/dev/i2c-2
DDC/CI supported: Yes
Monitor Name: SyncMaster 245B
Input type: Digital- Device: dev:/dev/i2c-1
DDC/CI supported: Yes
Monitor Name: SyncMaster 245B
Input type: Digital
from ddcutil.
Just to confirm, have you checked that the DisplayPort connection fails with multiple cables? If so, it's clearly a problem in the monitor's DDC/CI implementation.
@legodev and @razamatan Please run ddcutil detect --verbose 2>&1 and ddcutil environment --verbose 2>&1 when connected using displayport. This may give more information as to how DDC communication is failing. Your monitor can be set to several DisplayPort versions. Does communication fail with all?
Please also run ddcutil interrrogate for the HDMI connection that works. I would like to see details about the features of this monitor.
I have a Samsung U32H750 which from the manuals appears similar to the Odyssey G9 . See my monitor notes It has one of the poorest DDC implementations I've seen in a long time.
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@rockowitz Did not try another cable yet, as i don't have another one that is long enough.
My current cable is a rather expensive one, the search term: "KabelDirekt - 8K DisplayPort Kabel Version 1.4" - this cable is VESA certified and does support DP8K.
The output you requested did not change from my post a few months ago: #19 (comment)
There i did both via Displayport and via HDMI. Sadly not with the same GPU, due to the cable length, if you really think its the cable, then i can try via my egpu (which now contains the Vega 56 which i used in my previous comment)
Edit: i see i did not include the detect in my previous post, therefore i attach it here.
detect.txt
Edit2: the "DDC communication failed" on the 2 old SyncMasters is the case, because they where powered off.
Edit3: fixed a typo with the cable length
Edit4: added my current DisplayPort cable name.
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@legodev No, I don't think the problem is the cable. My suggestion to try a different cable was in the category of dotting i's and crossing t's, to absolutely rule out the cable. @razamatan has the same problem, and it's extremely unlikely that both of you have bad cables.
Based on the information I have so far, I have created an entry the rogues gallery of monitors.
One last thing to verify is that the problem occurs with both DisplayPort inputs, and is unaffected by the chosen DisplayPort version.
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I can confirm, that for me it did not work for both DisplayPorts (with Version 1.4, tested previously)
Tested DisplayPort versions on Port 1 with ddcutil detect --verbose
and version changed via OSD:
- 1.2 -> not working
- 1.1 -> not working
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@razamatan That statement from the Display Data Channel wikipedia page is confused. It seems to be saying that, if a Dual-Mode DP connector is not operating in alternative DVI/HDMI mode, but is instead operating in normal DisplayPort mode, then DDC is not supported. That is flat out wrong.
DisplayPort connectors have no dedicated DDC pins. They have pins for the DisplayPort AUX channel. DDC is implemented using the AUX channel, but the AUX channel itself is not DDC. It is general purpose channel that can carry, for example, USB. DisplayPort does not have the I2C SLA/SLC pins (sometimes referred to in this context as DDC pins). See the table at the top of page DisplayPort
A video card with Dual-Mode DP connectors is able to detect that it is communicating with a DVI or HDMI connector at the other end. Per Display Port Dual Mode, "Devices which implement dual-mode will detect that a DVI or HDMI adapter is attached, and send DVI/HDMI TMDS signals instead of DisplayPort signals." In that case the usage of the DisplayPort pins changes, and what are normally the AUX channel pins instead become DDC pins. See the table in the above cited section. A passive adapter routes the pins accordingly, and adjusts voltage levels.
A Dual-Mode DP connector operates as normal when it is communicating with a DisplayPort connector, either on the monitor itself or on an active adapter. An active adapter takes normal DP input on one end, and converts it to DVI/HDMI on the other end. (There are also active adapters that convert DVI/HDMI to DP. I am unaware of any bidirectional adapters.) The DDC (i.e. I2C) signals should be converted as well - if not the EDID could not be read, but it is possible that some active adapters only perform enough conversion to allow for reading the EDID. From the video card's point of view, an active adapter is just a normal DisplayPort connection.
Most video card DisplayPort connectors these days are dual mode, but there may be limitations on the number of connectors that can operate in alternate mode.
That all said, we are left with what you were told in your Samsung chat: The monitor does not support DDC on its DisplayPort connector.
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So please correct me if I didn't understand something. The lack of DDC in the Samsung G9 Monitor is based on a lack of pins/hardware in its connector or is this something which could be still solved by an update?
Are there alternative ways to adjust brightness or volume if there is no DDC??
from ddcutil.
@Erik262 The absence of DDC when using the G9s DisplayPort connection is not a matter of pins. It may be lack of hardware in the monitor, it may be the firmware. DisplayPort does not have dedicated pins for DDC. Instead, it has pins for what is called its AUX channel. DDC, along with many other types of signals, is "multiplexed" over the AUX channel. So the device at either end of a DisplayPort connection, whether video adapter card or monitor, needs to know how to transmit DDC over the AUX channel. To what extent the inability of the monitor support DDC over DisplayPort is a hardware or firmware problem depends, I suppose on the monitor.
You can still use the HDMI connector on the monitor for DDC. That is supported. You have 4 options for a physical connection.
-
HDMI connector on video adapter to HDMI connector on the monitor, using a HDMI-HDMI cable.
-
DVI connector the the video adapter to HDMI connector on the monitor. DVI and HDMI are essentially the same electrically. It's just a matter of routing the appropriate pins on one connector to the corresponding pins on the other.
-
DisplayPort connector on the video adapter to active converter to HDMI connector on the monitor. An "active converter" has the circuitry to convert DP signals to HDMI/DVI signals. The DisplayPort connector on the video adapter thinks it is communicating with a DisplayPort connector on the monitor, and the HDMI connector on the monitor thinks it is communicating with a HDMI connector on the video adapter. Active converters will be labelled "Active".
-
If the video adapter implements Display Port Dual Mode (most do), then it is possible to use a "passive converter" between the DisplayPort connector on the video adapter and the HDMI connector on the monitor. In this situation the video adapter detects that its DisplayPort connector is connected to an HDMI connector on the monitor and modifies its signalling mechanism to the protocol TDMS protocol used by HDMI and DVI. It also uses what are normally the AUX channel pins as simple I2C SDA/SDL pins for communicating DDC. The passive adapter simply routes the wires appropriately, with some voltage adjustment. So the video adapter is in essence using it's DisplayPort connector as a weird HDMI connector to communicate with the HDMI connector on the monitor. Video card DisplayPort connectors that support dual mode should be marked as such. In practice, the connectors on most recent video cards are dual mode, though they area commonly not marked as such.
from ddcutil.
i've left feedback to samsung support requesting support for ddc over dp connections for the g9. unfortunately, there's no way to track.
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This is really super disappointing. I really want DDC/CI over DisplayPort on the Samsung Odyssey G9.
I used to be able to have the brightness automatically change depending on the time of day with my old monitor (over DisplayPort) but this new 'top of the line' monitor can't.. :(
Adding this comment to add my support and track this thread.
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- DisplayPort connector on the video adapter to active converter to HDMI connector on the monitor. An "active converter" has the circuitry to convert DP signals to HDMI/DVI signals. The DisplayPort connector on the video adapter thinks it is communicating with a DisplayPort connector on the monitor, and the HDMI connector on the monitor thinks it is communicating with a HDMI connector on the video adapter. Active converters will be labelled "Active".
- If the video adapter implements Display Port Dual Mode (most do), then it is possible to use a "passive converter" between the DisplayPort connector on the video adapter and the HDMI connector on the monitor. In this situation the video adapter detects that its DisplayPort connector is connected to an HDMI connector on the monitor and modifies its signalling mechanism to the protocol TDMS protocol used by HDMI and DVI. It also uses what are normally the AUX channel pins as simple I2C SDA/SDL pins for communicating DDC. The passive adapter simply routes the wires appropriately, with some voltage adjustment. So the video adapter is in essence using it's DisplayPort connector as a weird HDMI connector to communicate with the HDMI connector on the monitor. Video card DisplayPort connectors that support dual mode should be marked as such. In practice, the connectors on most recent video cards are dual mode, though they area commonly not marked as such.
Does the 3rd and 4th option takes away all the advantages over DP 1.4? Like, will I be able to run 5120x1440 240 Hz HDR with 3rd or 4th option? Just wanted to confirm.
from ddcutil.
I do not have the expertise to comment specifically on resolution by DP and HDMI version. However, I can make the following general statements:
-
Does the HDMI input on the monitor support the desired resolution? If not, using a DP connector/signal at some point in the chain is irrelevant.
-
Does the HDMI output on the video adapter as well as the input on the monitor support the desired resolution? If so, I imagine option 4 would work. The video adapter is just treating its DP connector as a HDMI connector.
-
Do both the DP output on the video adapter and the HDMI input on the monitor support the desired resolution? In that case it's a question of whether the active adapter being used supports the desired resolution.
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Anyone have it working intermittently on one DP, but not another? Also I had it working consistently with the iGPU in the same computer where the dGPU would not. Both dGPU & iGPU were AMDGPU-driven, but the iGPU was over HDMI.
In the case when it isn't working ddcutil detect --verbose
shows:
DDC communication failed. (getvcp of feature x10 returned Error_Info[DDCRC_RETRIES in ddc_write_read_with_retry, causes: DDCRC_DDC_DATA(10)])
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