On Thu, 07 May 2015, Maxime Ripard wrote: > On Fri, May 01, 2015 at 07:44:05AM +0100, Lee Jones wrote: > > > > Does Sascha's antidote patch change your opinion? We can use DT to > > > > declare critical clocks, and in the rare case of the introduction of a > > > > new DDRFreq-like feature, which doesn't adapt the DT will still be > > > > able to unlock the criticalness of the clock and use it as expected? > > > > > > Honestly I'm not very fond of declaring these in the device tree, but > > > > I know why you guys are saying that, but I'd like you to understand > > the reasons for me pushing for this. Rather than be being deliberately > > obtuse, I'm thinking of the mess that not having this stuff in DT will > > cause for clock implementations like ours, which describe more of a > > framework than a description. > > The DT should dictate our implementation, not the other way around. I > know that we are pretty bad at doing this, and that there's some clear > abstraction violations already widely used, but really, using this > kind of argument is pretty bad. I guess then you haven't correctly understood my argument, as that's exactly what's happened. We have a DT implementation which accurately describes the clock architecture on each of our platforms. The associated C code in drivers/clk/ is written to extract the information from it, the hardware description and register the clocks properly. What makes you think differently? > The DT can (and is) shared between several OS and bootloaders, what if > the *BSDs or barebox, or whatever, guys come up with the exact same > argument to make a completely different binding? > > We'd end up either in a deadlock, or forcing our solution down the > throat to some other system. I'm not sure any of these outcomes is > something we want. Not sure I understand why this is different from any other binding? > > The providers in drivers/clock/st are blissfully ignorant of platform > > specifics. Per-platform configuration is described in DT. > > Maybe they just need a small amount of education then. Easy to say (and implement), but that means duplicating the hardware description in DT, which is not a design win. > > So we'd have 2 options to use a C-only based API; 1) duplicate > > platform information in drivers/clk/st, or 2) supply a vendor > > specific st,critical-clocks binding, pull out those references then > > run them though the aforementioned framework. It is my opinion that > > neither of those methods are desirable. > > 3) have a generic solution for this in the clock framework, like Mike > suggested. Did you actually read and understand the points here? If not, just say so and I'll figure out a way to explain the issues better. 3) is not an alternative to 1) and 2). Instead 1) and 2) imply 3). I *want* to have a generic solution, and have made several passes at writing one. The question here is; what does that look like? Some people don't like the idea of having it in DT due to possible abuse of the property. But we can't have anything only in C because our clock implementation (rightly) doesn't know or (shouldn't have to) care about platform specifics. Instead all platform description is in DT, where it should be. So to specify critical-clocks we need either 1) or 2) above to pull the info out and send to 3). -- Lee Jones Linaro STMicroelectronics Landing Team Lead Linaro.org │ Open source software for ARM SoCs Follow Linaro: Facebook | Twitter | Blog -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
