Hello Again Stephen, I did already send v5 prior to your reply but I will create v6 today based on this discussion. On Mon, Dec 03, 2018 at 03:35:10PM -0800, Stephen Boyd wrote: > Quoting Matti Vaittinen (2018-11-30 02:50:22) > > Hello Stephen, > > > > Thanks a bunch for taking the time and reviewing this! > > > > On Fri, Nov 30, 2018 at 12:54:10AM -0800, Stephen Boyd wrote: > > > Quoting Matti Vaittinen (2018-11-13 03:55:58) > > > > -int devm_of_clk_add_hw_provider(struct device *dev, > > > > +static int __devm_of_clk_add_hw_provider(struct device *dev, > > > > struct clk_hw *(*get)(struct of_phandle_args *clkspec, > > > > void *data), > > > > - void *data) > > > > + struct device_node *of_node, void *data) > > > > { > > > > - struct device_node **ptr, *np; > > > > + struct device_node **ptr; > > > > int ret; > > > > > > > > ptr = devres_alloc(devm_of_clk_release_provider, sizeof(*ptr), > > > > @@ -3906,10 +3906,9 @@ int devm_of_clk_add_hw_provider(struct device *dev, > > > > if (!ptr) > > > > return -ENOMEM; > > > > > > > > - np = dev->of_node; > > > > - ret = of_clk_add_hw_provider(np, get, data); > > > > + *ptr = of_node; > > > > + ret = of_clk_add_hw_provider(of_node, get, data); > > > > if (!ret) { > > > > - *ptr = np; > > > > > > Why is this moved outside of the if condition? > > I completely removed the local variable np and just unconditionally set > > the allocated devres to point at the node (if allocation succeeded). We > > could of course only do this if the provider registration succeeded and > > save one assignment - but I guess I intended to remove the curly braces > > and thus decided to go for one liner after if. But apparently I didn't > > remove the braces O_o. Well, I can put the assignment inside the > > condition if you prefer that. > > > > > In fact, why isn't just > > > the first line in this hunk deleted and passed to this function as > > > struct device_node *np? > > > > I am sorry but I don't quite follow your suggestion here. Do you mean we > > could just pass the struct device_node *np in devres_add()? I thought > > the pointer passed to devress_add() should be allocated using > > devres_alloc. Can you please elaborate what you mean? > > I'm just trying to reduce the diff in the patch. Oh, right. I will see how renaming the argument to np would impact to patch size. iActually, I never consider the patch size at all - I have only been concentrating on how the resulting file looks like. It didn't ever cross my mind that patch size matters. But I guess the size of chanes is really meaningfull when the amount of changes is large. > > > > devres_add(dev, ptr); > > > > } else { > > > > devres_free(ptr); > [..] > > > > > > > +int devm_of_clk_add_hw_provider(struct device *dev, > > > > + struct clk_hw *(*get)(struct of_phandle_args *clkspec, > > > > + void *data), > > > > + void *data) > > > > +{ > > > > + return __devm_of_clk_add_hw_provider(dev, get, dev->of_node, data); > > > > +} > > > > EXPORT_SYMBOL_GPL(devm_of_clk_add_hw_provider); > > > > > > > > +int devm_of_clk_add_parent_hw_provider(struct device *dev, > > > > + struct clk_hw *(*get)(struct of_phandle_args *clkspec, > > > > + void *data), > > > > + void *data) > > > > +{ > > > > + return __devm_of_clk_add_hw_provider(dev, get, dev->parent->of_node, > > > > > > I'm wondering if we can somehow auto-detect this in > > > devm_of_clk_add_hw_provider() by looking for #clock-cells in the node. > > > If it isn't there, then we go to the parent node and look for a > > > #clock-cells property there in the DT node for that device. Does that > > > make sense? Then there isn't any new API and we can attach the lifetime > > > of the devm registration to the presence of the property indicating this > > > is a clk controller or not. > > > > Huh. I don't know why but building this kind of logic in core is a bit > > scary to me. I guess I can try implementing something like this - but I > > am not really a fan of this. (Accidentally) omit the #clock-cells from > > node and we go to parent node - I am a novice on this area but this > > sounds like a potential hazard to me. I believe the driver should know > > if it's properties should be in own or parent node - and if they are > > not, then there should be no guessing but error. The lifetime is topic > > where I would like to get information from you who know the kernel > > better than I do =) But I guess the parent node is there at least as > > long as the child device is alive. So for me the life time of > > get-callback is more crucial - but as I said, I don't understand the > > kernel in details so you probably know it better than me. But please let > > me know your final take on this and I will follow the guidance =) > > Please do the magic instead of adding another API. It makes things > simpler and will work for this case without having to change anything > besides of_clk_add_provider(). All right. Let's go on this direction then. > If the DT doesn't have the #clock-cells property in the node being > registered then calling clk_get() will fail for any consumer devices > that point to the node with a phandle and clock specifier. I don't > expect us to get very far into development if that's the case. Makes sense. So only potential thing to break is if someone out there has broken DT/driver - where they currently see this failure. Eg. they use node w/o #clock-cells as provider and where they try and fail controlling this clock - but ignore the error (and system just "works" with HW defaults). After this change they may actually succeed in controlling - but do control wrong clock. Not likely scenario (sure happens somewhere) - and it involves already broken design. So I agree with you. Besides, you are the maintainer for clk framework and thus get the most of the rain if **** hits the fan =D > Of course, we don't fail in of_clk_add_provider() if there isn't a > #clock-cells property in the node, we just happily add the node to the > provider list and carry on. I doubt anyone is failing to specify the DT > property, but maybe they are, in which case we could keep not failing > and just add the node of whatever we're called with originally if > neither the parent or the passed node have the #clock-cells property. I > wouldn't try to go any higher than one node above the current node and > look for a #clock-cells though. I think we should use parent device's node, not the paren node in DT, right? But I agree, we should only look "one level up in the chain". > > If this all still seems scary then don't worry about it, I'll implement > it myself. It still is somewhat "scary" - but I really would like to use the devm based provider registration in the bd718x7 driver so I will implement it in this series. The engineer version of the "living on the edge", you know =) Br, Matti Vaittinen -- Matti Vaittinen ROHM Semiconductors ~~~ "I don't think so," said Rene Descartes. Just then, he vanished ~~~