On Mon, Oct 3, 2016 at 6:11 PM, Jason Ekstrand <ja...@jlekstrand.net> wrote:
> On Tue, Sep 27, 2016 at 3:23 PM, Nanley Chery <nanleych...@gmail.com> > wrote: > >> On Tue, Sep 27, 2016 at 03:12:17PM -0700, Chad Versace wrote: >> > On Tue 27 Sep 2016, Nanley Chery wrote: >> > > On Tue, Sep 27, 2016 at 11:00:21AM -0700, Chad Versace wrote: >> > >> > > > As a consequence of that reasoning, we should set >> 3DSTATE_CLEAR_PARAMS.DepthClearValueValid = 1 >> > > > whenever hiz is enabled, even if we don't care about the actual >> clear value. >> > > The logic seems to imply that we can't trust the context to save/restore > our depth clear value so we have to set it every time. At the very least, > once per batch? In any case, I doubt there's all that much cost involved > in emitting 3DSTATE_CLEAR_PARAMS so I don't think re-emitting it is that > big of a deal. > Thinking about it a bit more... We only set up dept/stencil packets once per subpass and we only do clears once per subpass so... I don't think we're actually saving anything by emitting it at clear time rather than at depth/stencil setup time. It is a bit more convenient because the clear values may be more accessible at clear time. As far as "should we emit 3DSTATE_CLEAR_PARAMS all the time?" Let's not go to any heroics to try and avoid re-emitting it. Once per subpass is not a big deal at all. --Jason > > > >> > > In the V3, I plan to emit that packet once at device initialization >> time >> > > HSW+, and to always emit it (in the expected location) for IVB/BYT. >> Only >> > > the latter platforms have the restriction that it must always be >> > > programmed with the other depth/stencil commands. >> > >> > Is there any benefit to emitting it multiple times on ivb/byt? Does >> > emitting once during initialization, as for hsw, also work for ivb/byt? >> > If so, the code is cleaner if the two gens share the same workaround >> > code. >> >> The benefit for emitting it multiple times on IVB/BYT is that we're >> (possibly) following the oddly-worded programming note for the packet: >> >> From the IVB PRM Vol2P1, 11.5.5.4 3DSTATE_CLEAR_PARAMS: >> >> 3DSTATE_CLEAR_PARAMS must always be programmed in the along with >> the other Depth/Stencil state commands(i.e. 3DSTATE_DEPTH_BUFFER, >> 3DSTATE_STENCIL_BUFFER, or 3DSTATE_HIER_DEPTH_BUFFER) >> >> HSW+ doesn't have this restriction, so we're free to only do it once. >> > >
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