Radeon HD 4250: screen going blank every few seconds

[Tijl Coosemans]

On Mon, 31 Dec 2018 14:56:17 +0100 Andrea Venturoli <ml at netfence.it> wrote:
> On 12/31/18 8:08 AM, Andrea Venturoli wrote:
>> I think I did it right, since "hw_i2c forced on, you may experience 
>> display detection problems!" is gone from Xorg.log.
>> However, it didn't help with the screen going blank.  
> 
> Sorry, I was too fast about this, as I had misspelled the line in 
> /boot/loader.conf.
> 
> When correctly written, the machine boots, but as soon as the kmod is 
> loaded:
> _ if the screen is connected via VGA connector, everything is fine (but 
> this is also true without this setting);
> _ if the screen is connected via HDMI, it goes blank for good (can't 
> interact with the system anymore and have to reboot);
> _ if the screen is connected via DVI, resolution goes to 1024x768 and 
> that's the maximum available even after X11 is started.
> 
> So, this is a no go.

Software i2c needs this patch:
https://github.com/FreeBSDDesktop/kms-drm/commit/6a3d6e69ab5bf47756fde2a7c00e3f7d6295c10f.patch

Save it as graphics/drm-fbsd11.2-kmod/files/patch-i2c and delete "a/"
and "b/" from the file.  Then rebuild drm-fbsd11.2-kmod.