On Mon, Feb 08, 2016 at 03:17:11PM +0000, Joao Pinto wrote: > Hi Mark and Arnd, > > I am planning the v2 of this patch set. I have a doubt in the version > compatibility strings... The core driver must support the UFS 2.0 controller and > this patch set includes a patch that adds 2.0 capabilities to it. Ok. It wasn't clear to me that this series added support for features specific to 2.0. > The core driver can get from the controller's version and with that > use or not a specific 2.0 feature. It can be detected from the hardware? > What would be the real added-value of having a compatibility string like > "snps,ufshcd-1.1" and "snps,ufshcd-2.0" if the driver can perform as 2.0 if it > detects a 2.0 controller? Generally having specify strings ensure that it's possible to handle things in future (e.g. errata workarounds), or if we realise something isn't as clear-cut as we thought it was (i.e. 2.0 not being a strict superset of 1.1). It's difficult to predict when you need that, so we err on the side of requiring it. At worst it means you have a small redundant few characters in a DT, but that's a much better proposition than having too little information. > Are you saying that a user that puts "snps,ufshcd-1.1" > in the DT compatibility string disables the UFS 2.0 in the core driver despite > the controller is 2.0? Please clarify. If you can consistently and safely detect that the HW is 2.0, using 2.0 functionality is fine. Regardless, you should have a -1.1 compatible string for the 1.1 HW, and a -2.0 string for the 2.0 HW, so that DTs are explicit about what the hardware is. If 2.0 is intended to be a superset of 1.1, you can have a 1.1 fallback entry for the 2.0 hardware. Thanks, Mark. -- 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
