On Tue 14 Jul 10:12 PDT 2020, Eric Biggers wrote: > On Tue, Jul 14, 2020 at 10:59:44AM -0600, Rob Herring wrote: > > On Tue, Jul 14, 2020 at 10:43 AM Eric Biggers <ebiggers@xxxxxxxxxx> wrote: > > > > > > On Tue, Jul 14, 2020 at 10:35:12AM -0600, Rob Herring wrote: > > > > On Tue, Jul 14, 2020 at 10:15 AM Eric Biggers <ebiggers@xxxxxxxxxx> wrote: > > > > > > > > > > On Tue, Jul 14, 2020 at 10:16:04AM -0400, Martin K. Petersen wrote: > > > > > > > > > > > > Eric, > > > > > > > > > > > > > Add the vendor-specific registers and clock for Qualcomm ICE (Inline > > > > > > > Crypto Engine) to the device tree node for the UFS host controller on > > > > > > > sdm845, so that the ufs-qcom driver will be able to use inline crypto. > > > > > > > > > > > > I would like to see an Acked-by for this patch before I merge it. > > > > > > > > > > > > > > > > Andy, Bjorn, or Rob: can you give Acked-by? > > > > > > > > DTS changes should go in via the QCom tree. > > > > > > > > > > So, the DTS patch can't be applied without the driver patches since then the > > > driver would misinterpret the ICE registers as the dev_ref_clk_ctrl registers. > > > > That sounds broken, but there's no context here for me to comment > > further. DTS changes should work with old/stable kernels. I'd suggest > > you get a review from Bjorn on the driver first. > > > > The "breaking" change is that the dev_ref_clk_ctrl registers are now identified > by name instead of assumed to be index 1. > > A reviewer had complained about the device-mapper bindings of this driver before > (https://lkml.kernel.org/r/158334171487.7173.5606223900174949177@xxxxxxxxxxxxxxxxxxxxxxxxxx). > Changing to identifying the registers by name seemed like an improvement. > > If needed I can add a hole at index 1 to make the DTS changes work with > old/stable kernels too, but I didn't know that is a requirement. (Normally for > Linux kernel development, kernel-internal refactoring is always allowed > upstream.) If I do this, would this hack have to be carried forever, or would > we be able to fix it up eventually? Is there any deprecation period for DTS, or > do the latest DTS have to work with a 20 year old kernel? > The problem here is that DT binding refactoring is not kernel-internal. It's two different projects living in the same git. There's a wish from various people that we make sure that new DTS continues to work with existing kernels. This is a nice in theory there's a lot of examples where we simply couldn't anticipate how future bindings would look. A particular example is that this prohibits most advancement in power management. But afaict what you describe above would make a new kernel failing to operate with the old DTS and that we have agreed to avoid. So I think the appropriate way to deal with this is to request the reg byname to detect the new binding and if that fails then assume that index 1 is dev_ref_clk_ctrl. There are cases where we just decide not to be backwards compatible, but it's pretty rare. As for deprecation, I think 1-2 LTS releases is sufficient, at that time scale it doesn't make sense to sit with an old DTB anyways (given the current pace of advancements in the kernel). Regards, Bjorn
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