15hz resolutions

[tandrews]

System is using a ATI Radeon card

I am looking for some information on why I can't Ubuntu 18.10 properly outputting 15hz. I built a 14.04 version and it works fine. I did this by making a custom x11 conf file which set the mode. Whats odd is the mode is being set in 18.10 and used but the output is wrong. I can get 31hz resolutions working like 640x480, that actually works perfectly but not 320x240. Obviously this resolution doesn't work on an actual monitor due to it being wrong freq. I generated the modeline using cvt.

I am aware of the 15hz linux project but I guess I'm just confused why 14.04 worked but 18.10 doesn't. I would presume the issue is major differences in the Kernel or Radeon driver. I have tried the provided .conf they use but that still didn't work.

I set the vga and video kernel boot params too, but that didn't seem to make much of a difference.

Is there anything I may be missing?

[Doozer]

Hi,

The pixel clock is indeed limited in the stock Radeon kernel driver. Distro specific kernel version might have additional patches applied. It could the case of Ubuntu 14.04.

The best solution is to compile your own kernel with 15khz patch applied.

[ZoOl007]

Hi,

Doozer is correct in my opinion.
I don't use ubuntu but from what you write I deduct that the running kernel in the 18.10 distro doesn't support 15khz and truth be told I find it odd the 14.04 one does.
I don't understand what you mean when you say you built a 14.04 one - you mean you built a kernel? Because that's what you need to do for your radeon to work.
A while ago I built myself one and I modified the diff's for the radeon to work with that kernel's sources. I'll attach them. To my knowledge they are the most current ones that exist.
I documented it for myself and I'll copy paste the md file I created.
It's not exactly copy paste for the reader but you should be able to work your way through and you'll need all the build dependencies.

You don't need to use a custom x11 cfg - follow the custom edid instructions in the attached archive

###begin md

TODO : doesn't work with kernel 4.15

The diff files have been modified to patch a 4.14 kernel from kernel.org

#fetch the archive
wget https://cdn.kernel.org/pub/linux/kernel/v4.x/linux-4.14.tar.xz
#extract it
tar -xf ./linux-4.14.tar.xz
#navigate to extracted directory
cd /home/********/kernel/linux-4.14.14/linux-4.14.14
#apply patches
patch -p1 < ../../linux-15khz-patch-master/linux.diff
patch -p1 < ../../linux-15khz-patch-master/ati9200_pllfix.diff
patch -p1 < ../../linux-15khz-patch-master/avga3000.diff
#edit its makefile so we will be able to see the modified kernel name in the grub menu
nano MakeFile
*    change EXTRAVERSION = to EXTRAVERSION = -15khz
#obtain super user rights
su
#install kernel header files from currently running kernel to obtain .config
apt-get install linux-headers-$(uname -r)
#locate the contained .config file
find / -name .config
#and copy it to the location where we extracted the kernel from kernel.org
cp /usr/src/linux-headers-4.9.0-5-amd64/.config .
#check if the following option is ON or we won't be able to load our custom edid
cat .config | grep CONFIG_DRM_LOAD_EDID_FIRMWARE
    CONFIG_DRM_LOAD_EDID_FIRMWARE=y reads y? -> ok
#compile the kernel
make -j$(nproc)
* answer defaults to all .config new parameters (just enter all the time)
* kernel compiles - took 90 minutes on test system
make modules_install
make install
#follow instructions in linux-15khz-patch-master/README.md file to apply edid when loading

###end md

If you modify the diff's to work with the latest stable 4.19.6 I kindly ask to post them back please.

Also, use the edid_arcade15.bin as it is the most flexible one for a scart tv. You'll need it for groovyMame

kind regards

[Arcade-TV]

It's not exactly copy paste for the reader but you should be able to work your way through and you'll need all the build dependencies.

I know I'm late for the party, I'm sorry, but could you please point out how to get the dependencies for this?

I tried:
sudo apt-get build-dep linux-image​ linux-image-4.14​
-> E: Unable to find a source package for linux-image-4.14​

I'm unable to find the exact name of the 4.14 image (supposedly 'generic'?)
plus my sources.list seems seems to be missing an URL for this. (# removed for active source URLs)

Thank You!

[ZoOl007]

apt-get install build-essential && gcc && g++ && linux-headers-$(uname -r) && bison && flex && bc && libssl-dev && libelf-dev

kind regards