Hi 2013/3/17 Daniel Vetter <daniel at ffwll.ch>: > On Wed, Mar 06, 2013 at 08:03:17PM -0300, Paulo Zanoni wrote: >> From: Paulo Zanoni <paulo.r.zanoni at intel.com> >> >> This solves many "unclaimed register" messages when the power well is >> down and we get a GPU hang. >> >> Also print the power well register and each pipe's CPU transcoder on >> the error state to allow proper interpratation of the registers. And >> kzalloc the error state structure since we may not read some of the >> registers (to avoid the "unclaimed register" messages). >> >> Signed-off-by: Paulo Zanoni <paulo.r.zanoni at intel.com> > > Ok, I've thought some more about all and you're all going to hate me. > > Essentially I don't like that we have rather invasive patches for a minor > feature with _very_ delicate limits as to what hits the debug yelling and > what doesn't. Furthermore the debug feature isn't that clear-cut since > interrupts get in the way (and we cant fix that since that would also > disable underrun interrupts, which we want). And the audio driver also > randomly inteferes. > > Now where it's justified that a register doesn't exist I don't mind > merging the patches - it's always good to have accurate documentation of > what's really used by the hw. But for debug features I'm really uneasy > with runtime checks, since it might very well be that those are wrong. > > Hence I vote for a I915_READ_NOCHECK to avoid all this madness. This one > will never check for errors, but silently clear them after a read. Note > that we don't need a I915_WRITE_NOCHECK, and imo that's good since writing > random crap could indeed be a serious bug. I don't understand your way of thinking: your argument is that "this is difficult to maintain", but then you're proposing the addition of a new i915_read, which IMHO is way much more complex and feels like a hackish solution to the problem. Every patch to the "normal" i915_read#x will have to also patch i915_read_nocheck#x. And on patch 0014, which you also suggested to use the "I915_READ_NOCHECK" function, our code will be relying on the _coincidence_ that when we read a register that does not exist, we read 0. I really don't think this is a sane approach. Our hardware is getting much more complex with respect to these reads, and I think we should never read ever read from a register that does not exist or is powered off. I'm open to more suggestions on how to write this patch, but I really think we shouldn't read registers that don't exist or are powered off. > > So I'll punt on this patch since imo it's too messy for future > maintenance. Same for the other debug patches (e.g. the assert_pipe_enabled > check). > > Cheers, Daniel > -- > Daniel Vetter > Software Engineer, Intel Corporation > +41 (0) 79 365 57 48 - http://blog.ffwll.ch -- Paulo Zanoni
