Hi
I'm going to start with some context which is not directly related to my question.
I'm experimenting with video resolutions on my rpi 400. I want to make it use a display with 1366x768 resolution (it's a TV). I found this link https://www.raspberrypi.com/documentati ... i-pipeline which says that the rpi 4 (and 400) do not support DMT mode 81, which is the standard 1366x768 resolution. I looked through the list of modes https://www.raspberrypi.com/documentati ... #hdmi-mode and found that there's a second 1366x768 resolution: DMT mode 86. So I tell config.txt that I want DMT mode 86:and for a brief moment during boot the display is indeed running flawlessly at 1366x768! But then the kernel boots properly and the magic is over, it falls back to 1920x1080 (it's a TV so it displays fine, but with a very ugly rescale).
So I look at the kernel parameters in /proc/cmdline and in /boot/cmdline.txt, and what I see is curious:
/proc/cmdline/boot/cmdline.txtThe kernel is being told to use 1366x768! But there is a catch: M. This M tells the kernel to use CVT to calculate the timings, instead of DMT. I can't change it because it's not in the cmdline.txt.
I'm still in the experimental phase, I know nothing for certain! But! I'm experimenting to find out, and I want to know how to remove the M from the command line, and see if anything different happens! How do I do it?
I'm going to start with some context which is not directly related to my question.
I'm experimenting with video resolutions on my rpi 400. I want to make it use a display with 1366x768 resolution (it's a TV). I found this link https://www.raspberrypi.com/documentati ... i-pipeline which says that the rpi 4 (and 400) do not support DMT mode 81, which is the standard 1366x768 resolution. I looked through the list of modes https://www.raspberrypi.com/documentati ... #hdmi-mode and found that there's a second 1366x768 resolution: DMT mode 86. So I tell config.txt that I want DMT mode 86:
Code:
[EDID=SAM-SAMSUNG][HDMI:1]hdmi_group=2hdmi_mode=86[all]So I look at the kernel parameters in /proc/cmdline and in /boot/cmdline.txt, and what I see is curious:
/proc/cmdline
Code:
coherent_pool=1M 8250.nr_uarts=0 snd_bcm2835.enable_headphones=0 snd_bcm2835.enable_hdmi=0 video=HDMI-A-1:1920x1080M@120 video=HDMI-A-2:1366x768M@60 smsc95xx.macaddr=DC:A6:32:D5:72:6B vc_mem.mem_base=0x3eb00000 vc_mem.mem_size=0x3ff00000 console=ttyS0,115200 console=tty1 root=PARTUUID=08b71eb1-02 rootfstype=ext4 fsck.repair=yes rootwait quiet splash plymouth.ignore-serial-consolesCode:
console=serial0,115200 console=tty1 root=PARTUUID=08b71eb1-02 rootfstype=ext4 fsck.repair=yes rootwait splash plymouth.ignore-serial-consolesI'm still in the experimental phase, I know nothing for certain! But! I'm experimenting to find out, and I want to know how to remove the M from the command line, and see if anything different happens! How do I do it?
Statistics: Posted by AstroSnail — Thu Dec 28, 2023 12:55 am