https://bugs.freedesktop.org/show_bug.cgi?id=98351
--- Comment #1 from Nicolai Hähnle nhaehnle@gmail.com --- Thank you for the report. I cannot reproduce this on Tonga. Does this still happen for you with a later kernel and/or Mesa git? There have been some hang fixes relatively recently.
Are there any messages in dmesg before the "ring stalled" messages?