On Mon, 2018-07-16 at 16:51 -0700, Marc Herbert wrote: > > > > > > > > I think the bug is with this infinite loop which is at the mercy > > > of an external device > > > and in my case I have this MST hub which appears to be DP 1.2 > > > that triggers the > > > infinite loop case. We have to limit the number of iterations and > > > DP 1.4 spec happened to fix this issue. I'm a newbie in this area > > > but in this case > > > shouldn't we apply the same counter to all <= "DP 1.4" devices? > > ok, the infinite loop situation is really bad... but I don't > > believe > > we are going with the right fix... > > and a good indication is that your fix is for DP-1.4 while your bug > > is seeing on DP-1.2 > I thought the only reason the infinite loop fix isn't in 1.2 is just > because there's > no 1.2.1 spec... (plus the naive assumption that buggy sinks don't > exist) > Irrespective of whether the sink is DP1.2 or 1.4, if there are sinks out there that keep toggling between two values there should be an overall limit to how many times this loop gets executed. Even if this isn't right fix for the issue at hand, the loop has to break. Then there's the question of what the limit should be. We could use the DP1.4 limit as a reference and apply it widely. But there's a problem here, we have 4 vswing values and 4 pre-emphasis values. If the sink progressively changes one variable at a time, we'll need at least 16 iterations. Nathan's patch here will prematurely error out and that doesn't sound reasonable to impose on non DP1.4 sinks. -DK > > > _______________________________________________ > Intel-gfx mailing list > Intel-gfx@xxxxxxxxxxxxxxxxxxxxx > https://lists.freedesktop.org/mailman/listinfo/intel-gfx _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/intel-gfx
