Daisy chain not working after firmware update

[w00t_f]

I have a Samsung LS27A600UUUXXU monitor which I connect via Type C to my laptop. 

I wanted to daisy chain this monitor to another HP E24 G4 which also is compatible with daisy chaining via DP port.

Earlier I was on Firmware M-A6U00SGZA-1007.0 version where the daisy chaining did work on both monitors. However, it would not detect the HP monitor if the laptop comes out of sleep status and I would either have to plug in / plug out the USB C cable from the laptop OR change the setting on the samsung monitor from MST -> SST -> MST (TypeC) to get the display detected & working. Once this is done, it would work fine till the laptop goes to sleep again. 

I contacted Samsung Customer care who informed I should update the Firmware to M-A6U00SGZA-1014.0 version. After doing this successfully, the HP monitor only detects on my laptop as a 3rd display, but nothing shows on it. Even after unplugging / plugging the Type C cable again OR switching the MST -> SST -> MST, it still does not display anything. 

Is there anyway to fix this or roll back to the previous firmware? I tried searching everywhere but could not find the 1007 firmware. I also reset the settings of both the monitors and that did not work.

My wife uses the same HPE24 G4 monitor with a Lenovo monitor over USB C and the daisy chaining works flawlessly there.

[jjwATmyself]

That's a real shame. The monitors with USB C are such a great concept. Something to try, Device Manager > View > Show Hidden Devices. Expand monitors and delete all the transparent (old) monitors. DisplayPort has all kinds of wake issues in Windows as it's treated like a PnP device. Another thing to test when you have the issue is press Win + Ctrl + Shift + B which resets the graphics driver.

[w00t_f]

Hey thanks for the suggestion. I deleted the old greyed out monitors and tried resetting the graphics driver also. Did not work. I even updated the HP monitor firmware to the latest. Not working. 

The weird part is the monitor detects in windows but does not display anything. its like something is preventing it. However, over HDMI, the monitor works fine.

[Thw0rted]

Did you ever get this working?

I just got the same monitor (27" ViewFinity S60UA), and I think I have the same problem.  It came with firmware v1010 and I updated to v1014.  The next day, I got a second monitor -- happens to be a Lenovo E24q-20, but I'm pretty sure that shouldn't matter as long as it has a DP input.  Anyway, if I set the Samsung display to SST mode, the Lenovo mirrors the Samsung without issues.  If I set it to MST, the Lenovo shows "no signal" and goes to sleep.  I'm driving it with a Dell XPS 9510 with Windows 11, using the USB-C input on the S60UA.  Windows does see two external displays, but the Lenovo won't actually show any picture.

I do have a two-output USB-C to DisplayPort hub, so I could connect the laptop to the hub, then both displays directly via DisplayPort.  If I could get daisy-chain / MST pass-through working, I could return the hub and the extra DisplayPort cable.

[w00t_f]

Nope, it only worked on 1007 firmware with a few hacks but once it worked, the monitor kept displaying till the laptop went back to sleep.

Samsung did not help here. If you're on 1010v firmware you cannot downgrade & you will not even find the firmware file anywhere. Basically I've reverted to 1 x hdmi and 1 x type C to use 2 monitors via laptop instead of daisy chaining. 

Also, the SST mode won't work. Has to be MST. 

Funny enough part is my wife has the same Lenovo E24q-20 with HP E24 G4 setup and it works flawlessly over there. It's an issue with this Samsung monitor firmware which these guys are not willing to fix. They blame the HP monitor, when I contact HP, they blame the Samsung monitor. typical

[Thw0rted]

I did some digging on Dell's forums to see if it was something particular to my laptop, and I might have come up with a theory.

• From what I've read, the laptop and the Samsung DP input both support DP  1.2, which has 4 "lanes".
• DP over USB-C (alt-mode) supports these 4 lanes and some kind of low-speed side channel.
• A single 1440p@75Hz display needs 2 lanes worth of bandwidth.
• The USB alt-mode "side channel" only supports USB 2.0, but you can take one of the 4 DP "lanes" to provide USB 3.x "superspeed".  Some USB-to-DisplayPort hubs only provide 2.0 ports, some have only 3.0 and don't support MST, and some have a toggle (2.0+MST or 3.0+SST).
• The USB-A ports on the back of this Samsung monitor are labeled "superspeed".

Adding that all up: it seems likely that the Samsung display can forward 2 lanes from a DisplayPort input, but only one lane from USB-C DP alt-mode, because with a USB connection it's using one lane for 3.0/superspeed support.  I think that if I get a USB-C to DisplayPort 1.2 cable, and connect it directly to the DP In port on the Samsung display, this will provide 4 lanes for display traffic, then the MST connection through to the Lenovo display should be able to use 2 lanes for a 1440@75 picture (at the expense of being unable to use the USB-A ports on the monitor).  I just ordered a cable to try this out, if it works I will probably just settle for a 2-cable solution, one for power + mouse etc, and one directly to the DP input.

[Thw0rted]

Update: I think you're right about an issue with Samsung's firmware.

The USB-to-DP cable arrived.  I'm now connected USB-C -> Samsung DP In, then Samsung DP Out -> Lenovo DP In, using the DP cable that came with the Samsung.  I'm seeing the exact same behavior as I was when using the Samsung USB-C input directly.  When I set the Samsung "DP Out" to DisplayPort SST, the Lenovo mirrors what's on the Samsung without issue, but if I set it to DisplayPort MST, the computer thinks there are two monitors connected but the Lenovo goes to sleep saying there is no signal.

I actually tried this on a second laptop just to rule out an issue with the graphics card on the first.  Exact same behavior on both a Dell XPS 9500, which has a GTX 1650 but the USB-C DP alt-mode connects to the Intel 650 onboard, as well as a Razer Blade 14 (2021 I think?) which connects the USB-C DP alt-mode to the RTX 3070 (confirmed in NVidia Control Panel).  Both show the Lenovo as a 3rd monitor in Display Settings, but in both cases the Lenovo has no picture.  Something is wonky with the MST pass-through.

[userLzBJA0kUIG]

I have exactly the same issue. I can see the monitor in windows display settings, but there's no video. And god, Samsung support are the worst. Spent almost 2 hours with the guy demanding a video to show the problem, to answer me with a screenshot of the cables installation guide in the manual. In the end he ask me to find a local shop to fix it, when all I was asking was the previous firmware version.

I was using the chain normally before the update and already tried everything - rollback image, backup image and reinstalling the firmware. Clearly is an issue with this version.

Also, the option for HDR disappeared. 

I'm looking for the previous version ( M-A6U00SGZA-1011.0 in my case) if someone find it, please reach out. I found a way to rollback.

[Thw0rted]

Did you try pointing the support folks to this thread?  Clearly it's impacting multiple users, it sounds like it should be escalated to a higher support tier for investigation.

I'd also really like to hear from anybody who is on a higher firmware than 1010, that is actually using MST out successfully.  If there's anybody it *doesn't* impact, maybe  we can figure out if we're doing something "wrong".

[w00t_f]

So Samsung support are saying that they're working on a fix for this. There is a reference number which I got so will update if anything comes up