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Linux 15kHz patches
Arcade-TV:
--- Quote from: Doozer on September 06, 2019, 04:20:10 am ---checked the log in the syslog or dmesg command?
--- End quote ---
dmesg had nothing unusual in it, besides some ACPI warnings that keep showing under Linux.
--- Quote from: Doozer on September 06, 2019, 05:15:15 am ---Hacking the hardware could allow another (any frequency) clock to be used as per following.
But I am not in favor of a hardware hack and it will only work for a predefined dot clock.
--- End quote ---
I'd like to mention that I'm much better with a soldering iron than with a Linux command line ;-)
--- Quote from: Doozer on September 06, 2019, 05:15:15 am ---It does not mean that the 25MHz is a fixed barrier, but only testing and playing with the PLL can reveal us the lower limit with appropriate stability.
--- End quote ---
Of course it would be really awesome to have more modelines available with this chipset, but if it seems like a dead end I'm not stressing to put time and energy into it.
Anyways, I'm open for suggestions and I have some spare time tonight.
Thank you very much for looking into this, still, it's very much appreciated!!
Doozer:
--- Quote ---
I'd like to mention that I'm much better with a soldering iron than with a Linux command line ;-)
--- End quote ---
Using an external clock to feed the display logic would make the solution too unique and not very practicable due to the need to configure the external clock each time you change the resolution.
Substring:
stupid question : 15khz patches are made to boot in 15khz besides patching a few things here and there. Isn't that a xorg driver problem ? Doozer I remember you saying me something like GM uses DRM, but that's not the case for the OS itself ! (was a few days ago when I asked if we had to patch xorg drivers to allow lower video modes like 160x100)
Doozer:
--- Quote from: Substring on September 09, 2019, 05:37:55 pm ---stupid question : 15khz patches are made to boot in 15khz besides patching a few things here and there. Isn't that a xorg driver problem ? Doozer I remember you saying me something like GM uses DRM, but that's not the case for the OS itself ! (was a few days ago when I asked if we had to patch xorg drivers to allow lower video modes like 160x100)
--- End quote ---
It is correct, the 15kHz patch allows the kernel to boot in 15kHz mode after the kernel is loaded. You can achieve the same result by specifying EDID with 15kHz mode on kernel line or via dongle. In your boot manager, you can append the following to the kernel line "video=VGA-1:e drm_kms_helper.edid_firmware=VGA-1:edid/edid_pal.bin".
X will configure itself to the provided EDID resolution. GM will switch resolution as usual by using the DRM calls.
xf86 library are indeed limited to 320x200 and must be patch to reach lower resolution. Which is not a requirement because they can be managed by GM integer scaling functionality.
Doozer:
The 15kHz patches towards freshly released kernel 5.3 are available.
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