Radeon HD 4250: screen going blank every few seconds

[Tijl Coosemans]

On Mon, 31 Dec 2018 18:36:46 +0100 Andrea Venturoli <ml at netfence.it> wrote:
> On 12/31/18 5:22 PM, Tijl Coosemans wrote:
>> 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.  
> 
> Thanks.
> I'll try this patch if what I've already done does not solve (see my 
> other message).
> 
> I like to understand what I'm doing, if possible, though; do you have 
> some pointers of what this I2C is (WRT to x.org), what it does, etc...?

It's a simple 2 wire bus used between components on a graphics card:
https://en.wikipedia.org/wiki/I2C

When hw_i2c is 0 the driver manages the I2C bus, when it's 1 the hardware
manages it.  The hardware implementation is often buggy, which is why
hw_i2c should default to 0.  It was set to 1 on FreeBSD because of a bug
in the driver (fixed by the patch above).  This only affects
drm-fbsd11.2-kmod.