Hi Felipe, On 14/12/18 4:17 PM, Felipe Balbi wrote: > Hi, > > Sekhar Nori <nsekhar@xxxxxx> writes: > > <snip> > >>>>> 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. 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. > Personally, I wouldn't bother. Just like dwc3 never bothered and nothing > bad came about because of it. Well, there are quirks which are > undetectable and for those we have quirk flags. I much prefer that > arrangement. Yes, quirk flags will work too for undetectable quirks. Thanks, Sekhar
