On 14/12/18 4:56 PM, Felipe Balbi wrote: > 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? When, for example, its coming in the way of some clean-up I am attempting to do. > >> 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. I know :). I should have stated that in last e-mail itself, I am okay with just runtime detection. Thanks, Sekhar
