Comment 33 for bug 311895

In #18491 there's a patch (https://bugs.freedesktop.org/attachment.cgi?id=22319) to mess with the FIFO watermark values that might help. But more than that, it includes a patch to dump the FIFO watermark regs to the intel_reg_dumper tool. Can someone apply it and capture a reg dump both before and after starting X on their machine with the patch applied?

The spontaneous black screen is almost surely caused by a series of pipe underruns. That generally happens if our memory arbitration settings are off (so a given pipe can't get its pixels due to some other pipe hogging the memory interface) or the FIFO watermark regs being incorrect (we fetch a new chunk of pixels too late and end up missing our window of time to feed them to the pipe).

The framebuffer compression hardware periodically compresses the framebuffer into a private section of memory (the compressed buffer), temporarily increasing memory activity; it could be that we're not accounting for that in the FIFO settings, so the screen goes black after the first compression pass (which is usually after about 15s iirc).