Hi, Sekhar Nori <nsekhar@xxxxxx> writes: >>>>>> All this should be part of comments in code along with information about >>>>>> controller versions which suffer from the errata. >>>>>> >>>>>> Is there a version of controller available which does not have the >>>>>> defect? Is there a future plan to fix this? >>>>>> >>>>>> If any of that is yes, you probably want to handle this with runtime >>>>>> detection of version (like done with DWC3_REVISION_XXX macros). >>>>>> Sometimes the hardware-read versions themselves are incorrect, so its >>>>>> better to introduce a version specific compatible too like >>>>>> "cdns,usb-1.0.0" (as hinted to by Rob Herring as well). >>>>>> >>>>> >>>>> custom match_ep is used and works with all versions of the gen1 >>>>> controller. Future (gen2) releases of the controller won’t have such >>>>> limitation but there is no plan to change current (gen1) functionality >>>>> of the controller. >>>>> >>>>> I will add comment before cdns3_gadget_match_ep function. >>>>> Also I will change cdns,usb3 to cdns,usb3-1.0.0 and add additional >>>>> cdns,usb3-1.0.1 compatible. >>>>> >>>>> cdns,usb3-1.0.1 will be for current version of controller which I use. >>>>> cdns,usb3-1.0.0 will be for older version - Peter Chan platform. >>>>> I now that I have some changes in controller, and one of them require >>>>> some changes in DRD driver. It will be safer to add two separate >>>>> version in compatibles. >>>>> >>>> >>>> Pawel, could we have correct register to show controller version? It is >>>> better we could version judgement at runtime instead of static compatible. >>> >>> Agree with detecting IP version at runtime. >>> >>> But please have some indication of version in compatible string too, >> >> why? Runtime detection by revision register should be the way to go if >> the HW provides it. Why duplicate the information in compatible string? >> >>> especially since you already know there is going to be another revision >>> of hardware. It has the advantage that one can easily grep to see which >>> hardware is running current version of controller without having access >>> to the hardware itself. Becomes useful later on when its time to >>> clean-up unused code when boards become obsolete or for requesting >>> testing help. >> >> This doesn't sound like a very strong argument, actually. Specially when >> you consider that, since driver will do revision checking based on >> revision register, you already have strings to grep. Moreover, we don't >> usually drop support just like that. > > AFAICS, it is impossible to know just by grep'ing if there is any > hardware still supported in kernel and using DWC3_REVISION_194A, for > example. but why do you even care? > If we are never going to drop support for any revision, this does not > matter much. > > Also, once you have the controller supported behind PCI, then I guess > you are pretty much tied to having to read hardware revision at runtime. that's another argument *for* using runtime detection, not against it. -- balbi
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