I have this weird behaviour with my AMD E-450 APU using the native radeon drivers. KMS initialization sometimes causes the screen to be full of various coloured pixels (and you see the contours of text in what I presume to be the black/white contrasts in the noise). Usually re-starting again once or a couple of times resolves the issue.
It almost seems like KMS is trying to initialize before the graphics of the APU has "heated up" if that makes any sense at all...
Anyone got an idea for a solution? Not critical but annoying.
btw: this problem has persisted over several kernel releases and radeon updates.
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I also have this CPU/GPU/APU and already filed a bug report. But I don't see "various coloured pixels", but only a black screen (although: one time I had white stripes on black ground, like a zebra)