DietPi Display Resolution Topic is solved

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jvfreitasj
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Joined: Sat Oct 03, 2020 4:29 am

DietPi Display Resolution

Post by jvfreitasj »

Please, could someone help about a Dell?

I have a QHD 2560 x 1440 @ 60 Hz display, I've tested several distros last week on my Pi4 and had full 2K resolution. The distro I liked the most was DietPi, but I'm struggling to understand the reason my display is recognized as a Full HD Display and I can't change it to a higher resolution at diet-config. I've installed the Mate Desktop and want to have a better resolution because it seems blur.

I also tried somes configs at config.txt, hdmi_group=1 and hdmi_group=97 but it didn't work. Plus hdmi_cvt=2560 1440 60 3 0 0 0.

Gave some "/opt/vc/bin/tvservice -m CEA" and "/opt/vc/bin/tvservice -m DMT" and the highest resolution it supports is 1080p. As I said, in many other distro I could get 2K.

One thing I realized is that on Mate it doesn't show the Brand and Model of my monitor as I can see in other distros.


Regards,

José
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Joulinar
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Re: DietPi Display Resolution

Post by Joulinar »

Hi,

many thanks for your report. Just one question. Was it working on Raspberry OS? Because DietPi for RPi devices is based on Raspberry OS and if it was working on Raspberry OS, it might be possible on DietPi as well. :?
Pls let us know if a solution is working. This could help others if they hit by similar situation. Your DietPi Team
jvfreitasj
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Joined: Sat Oct 03, 2020 4:29 am

Re: DietPi Display Resolution

Post by jvfreitasj »

Hello, I’ve tested Raspberry OS two days ago and I got 2K resolution without any further configuration!
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Joulinar
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Re: DietPi Display Resolution

Post by Joulinar »

Maybe @MichaIng has an idea what is missing compare to plain Raspberry OS
Pls let us know if a solution is working. This could help others if they hit by similar situation. Your DietPi Team
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MichaIng
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Re: DietPi Display Resolution

Post by MichaIng »

For 4k 60 Hz add hdmi_enable_4kp60=1 to config.txt: https://www.raspberrypi.org/documentati ... t/video.md

Code: Select all

G_CONFIG_INJECT 'hdmi_enable_4kp60=' 'hdmi_enable_4kp60=1' /boot/config.txt
The resolution you tried via hdmi_group=97 2160p = 3840 × 2160 which exceeds your monitor? There seems to be no mode that explicitly matches 2560 x 1440 :?.

Ah and basically dietpi-config does not support >1080p resolution yet, good to be reminded that this still needs to be done. So what you need to take care of:
- Either comment or set framebuffer_width and framebuffer_height to match your desired resolution.
- If you use hdmi_mode + hdmi_group, I think the framebuffer settings should be commented instead to not interfere.
- Or comment all video/hdmi related settings and check if auto-detection works fine.

Easiest should be to copy the config.txt from the OS that worked fine with your monitor over to DietPi, which should then behave the same then.
jvfreitasj
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Joined: Sat Oct 03, 2020 4:29 am

Re: DietPi Display Resolution

Post by jvfreitasj »

Dear MichaIng, thanks for your replay!

First of all, I made a mistake and got confused whit hdmi_group=97, saw 2160p and thought it was 2k, but its 4K. :(

Despite that mistake, I could solve the problem.

"- Either comment or set framebuffer_width and framebuffer_height to match your desired resolution."
A: Alone, it doesn't work!

"- If you use hdmi_mode + hdmi_group, I think the framebuffer settings should be commented instead to not interfere."
A: I created a custom resolution "hdmi_cvt=2560 1440 60 3 0 0 0", "hdmi_group=2" and "hdmi_group=87" but it didn't work.

"Or comment all video/hdmi related settings and check if auto-detection works fine."
A: I started with the default Dietpi config.txt and it didn't work.

"Copy the config.txt from the OS that worked fine with your monitor over to DietPi"
A: It made the trick!!! But why? I realized that Dietpi has a better config.txt file and better explanations compared against Raspberry Pi OS, but I found 2 interesting lines on Raspberry OS config.txt and would suggest you to evaluate them:

[pi4]
# Enable DRM VC4 V3D driver on top of the dispmanx display stack
dtoverlay=vc4-fkms-v3d
max_framebuffers=2

I know they made it work!
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MichaIng
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Re: DietPi Display Resolution

Post by MichaIng »

Great that it works now. Yes the default config.txt of Raspbian/Raspberry Pi OS is actually an ancient one that has never really been adjusted for any newer RPi model, e.g. I think the contained (commented) overclocking settings show RPi 1 defaults :).

With RPi 4 indeed those two settings have been added, below the [pi4] category, so only active there. The first is the GPU driver, actually that should not be relevant as long as you don't use any graphics software, including desktop, media players, browser or others.

The second enables the second HDMI connector. I'm not sure if, in case this is set to "1", the second connector is unusable or if the one framebuffer is attached automatically to the HDMI port where the single monitor is attached. To reduce memory usage it makes sense to set this to "1" as long as you only use one HDMI and use the 1. HDMI port then, if necessary.

So basically I would be surprised of any of this two settings is really required to display >1080p resolutions :?.

What I have not yet thought about is the GPU memory and framebuffer sizes. By default DietPi RPi images are shipped with minimal 16 MiB GPU memory split. I'm not sure if it can be calculated like this and not even sure if the framebuffer is hold in system memory or GPU memory (some things have been shifted from GPU to system memory with RPi 4), but 2560x1440 with default 16 bit depths would mean a minimum of 16/8 * 2560 * 1440 / 1024 / 1024 > 7 MiB which is the raw colour definition for every pixel. I guess there is some meta data around, but that's already half of the 16 MiB GPU memory.
Long story short, did you increase the GPU memory split as solution attempt? On Raspberry Pi OS it's 64 MiB, the default if not defined or commented.
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