Hi, On Tue, Apr 21, 2020 at 11:57:33AM +0200, Philipp Rossak wrote: > On 20.04.20 09:38, Maxime Ripard wrote: > > Hi, > > > > On Fri, Apr 17, 2020 at 02:09:06PM +0200, Philipp Rossak wrote: > > > > > I'm a bit skeptical on that one since it doesn't even list the > > > > > interrupts connected to the GPU that the binding mandates. > > > > > > > > I think he left it out for a future update. > > > > But best he comments himself. > > > > > > I'm currently working on those bindings. They are now 90% done, but they are > > > not finished till now. Currently there is some mainline support missing to > > > add the full binding. The A83T and also the A31/A31s have a GPU Power Off > > > Gating Register in the R_PRCM module, that is not supported right now in > > > Mainline. The Register need to be written when the GPU is powered on and > > > off. > > > > > > @Maxime: I totally agree on your point that a demo needs to be provided > > > before the related DTS patches should be provided. That's the reason why I > > > added the gpu placeholder patches. > > > Do you have an idea how a driver for the R_PRCM stuff can look like? I'm not > > > that experienced with the clock driver framework. > > > > It looks like a power-domain to me, so you'd rather plug that into the genpd > > framework. > > I had a look on genpd and I'm not really sure if that fits. > > It is basically some bit that verify that the clocks should be enabled or > disabled. No, it can do much more than that. It's a framework to control the SoCs power domains, so clocks might be a part of it, but most of the time it's going to be about powering up a particular device. > I think this is better placed somewhere in the clocking framework. > I see there more similarities to the gating stuff. > Do you think it is suitable to implement it like the clock gating? I'm really not sure what makes you think that this should be modelled as a clock? > > > The big question is right now how to proceed with the A83T and A31s patches. > > > I see there three options, which one do you prefer?: > > > > > > 1. Provide now placeholder patches and send new patches, if everything is > > > clear and other things are mainlined > > > 2. Provide now patches as complete as possible and provide later patches to > > > complete them when the R_PRCM things are mainlined > > > 3. Leave them out, till the related work is mainlined and the bindings are > > > final. > > > > Like I said, the DT *has* to be backward-compatible, so for any DT patch that > > you are asking to be merged, you should be prepared to support it indefinitely > > and be able to run from it, and you won't be able to change the bindings later > > on. > > I agree on your points. But is this also suitable to drivers that are > currently off tree and might be merged in one or two years? This is what we done for the Mali. The devicetree binding was first done for the out-of-tree driver, and then lima/panfrost reused it. The key thing here is to have enough confidence about how the hardware works so that you can accurately describe it. Maxime
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