Op 29-07-16 om 22:33 schreef Matt Roper: > On Fri, Jul 29, 2016 at 12:39:05PM +0300, Ville Syrjälä wrote: >> On Thu, Jul 28, 2016 at 05:03:52PM -0700, Matt Roper wrote: >>> This is completely untested (and probably horribly broken/buggy), but >>> here's a quick mockup of the general approach I was thinking for >>> ensuring DDB & WM's can be updated together while ensuring the >>> three-step pipe flushing process is honored: >>> >>> https://github.com/mattrope/kernel/commits/experimental/lyude_ddb >>> >>> Basically the idea is to take note of what's happening to the pipe's DDB >>> allocation (shrinking, growing, unchanged, etc.) during the atomic check >>> phase; >> Didn't look too closely, but I think you can't actually do that unless >> you lock all the crtcs whenever the number of active pipes is goind to >> change. Meaning we'd essentially be back to the one-big-modeset-lock >> apporach, which will cause missed flips and whanot on the other pipes. >> >> The alternative I think would consist of: >> - make sure level 0 watermark never exceeds total_ddb_size/max_pipes, >> so that a modeset doesn't have to care about the wms for the other >> pipes not fitting in > Unfortunately this part is the problem. You might get away with doing > this on SKL/KBL which only have three planes max per pipe and a large > (896 block) DDB, but on BXT you have up to four planes (we don't > actually enable the topmost plane in a full-featured manner just yet, > but need to soon), yet the total DDB is only 512 blocks. Sadly, the > platform with more planes was given a smaller DDB... :-( > We're already in trouble because users that are running setups like 3x > 4K with most/all planes in use at large sizes can't find level 0 > watermarks that satisfy their needs and we have to reject the whole > configuration. If we further limit each pipe's usage to total/maxpipes > (i.e., 170 blocks per pipe on BXT), then we're going to hit similar > issues when only driving one or two displays with with all of the planes > in use, even though we should have had more DDB space to work with. > > I guess serious plane usage isn't too common in desktop setups today, > but it's a very critical feature in the embedded world; we can't really > afford to cripple plane usage further. Unfortunately, as you point out > above, this means that we have to follow the bspec's DDB allocation > method, which in turn means we need to grab _all_ CRTC locks any time > _any_ CRTC is being turned on or turned off which is a BKL-style way of > doing things. Meh, I'm running into a similar issue on vlv/chv. I don't see a way around it. :( Only thing we could do is split up the state to make the non-modeset crtc's complete early. _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
