Hi Mark, On 2/8/2016 3:30 PM, Mark Rutland wrote: > 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. Yes, the patch set contains a patch to add 2.0 to the UFS core driver. The cover letter: https://lkml.org/lkml/2016/2/3/331 The Patch: https://lkml.org/lkml/2016/2/3/330 > >> 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? Yes, the hardware has a register that contains the version, and so if a driver has workarounds then it can adapt. > >> 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. > Ok, I will include the version in the compatibility strings, but if someone mentions "snps,ufshcd-1.1" only and the driver detects that the HW is 2.0 capable it will activate the 2.0 features independently of what mentioned in the DT, correct? > Thanks, > Mark. > Thanks, Joao -- 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
