I am trying almost everything except going back to old Windows (now I have W10 pro 1809). Nothing works.
If I reinstall the chipset driver, it works again untill... something that I don't know that again make the brightness controls useless.
Video driver is 126.96.36.19973 28/feb/2018
By the way: I have also an XPS15 9550 that has the same Win version and it has no problem.
I find it interesting that Dell update installs a different version on Intel graphics then what's on their web site for same model? Also add to the mix Windows 10 1809 has begun to install a universal type driver that is distributed through Windows updates. Causing havoc itself and so far all of the drivers for Intel graphics on my XPS 13 9360 have caused some sort of issue. Right now my brightness will not adjust at all without a reboot and that does not last very long. Is it really this hard to engineer a graphics driver that works for Intel??? Or is Win 10 1809 that messed up that its causing all these driver issues. This is the last time I buy a premium laptop, obviously Dell can't seem to provide any better support for it.
So here's what fixed brightness adjust for me. I went into Device Manager and uninstalled graphic driver and selected to delete driver from PC. Then I restarted PC and let Windows update install driver 188.8.131.5223. This has fixed brightness control. I also uninstalled Dell Update app because I am concerned it will install the bad driver again. Both Dell drivers are older and I don't think they work with Win 10 1809.
Not sure if my brightness stopped working from a recent update I did on the system, or it was triggered by the charging cord?? But the brightness on my laptop stopped working a few days ago.
I went on the Dell Support website, downloaded the "Intel HD 620 and Iris Graphics 640" which was all the way down at the bottom on the list of drivers, and installed it. Once installed and restarted, it worked perfectly fine and it adjusted the brightness to where it works properly now.
IF THAT DOESN'T WORK:
One small solution that can help is, if you right click anywhere on your desktop screen, scroll down to "Intel Graphics Settings", click on it and wait for the program to load. Then click "Display" and "Brightness" and that should somewhat help if it's too dim. Otherwise, check the support section or get in contact with a rep.
Not working in my case, or better... as in the case of chipset driver, reinstallation of video driver works perfectly ...for some time.
Then something happens that triggers again the problem and you are again without the brightness control.
Sorry, I gave wrong info
I have had this problem for a number of months now, and have monitored closely the discussions online. Let us be honest here: there is NO solution to this problem to date. I have followed Dell's advice to update everything; BIOS, drivers, ran hardware diagnostics (all passed), the last time being two days ago. Surely the brightness control does come back after all this, only to fail again *apparently* after the machine goes to sleep more than once.
For those who work sometimes into the night, such control is crucial. If the latest update clearly does not work (to anyone), then Dell released an update that was not tested properly and should stop telling customers to update their drivers, BIOS, etc. Worse yet, you can find online recent advice from Dell to "roll back" the drivers. What is this? It equates to saying "here is the latest, it's been automatically installed on your machine, but don't use it".
Dell, please solve the problem. As of now, your product does not work and is impacting the work of those who need is as their main tool. It equates to being a hammer without a handle.