On Mon, May 13, 2019 at 3:19 PM Sudeep Holla <sudeep.holla@xxxxxxx> wrote: > > On Fri, May 10, 2019 at 11:58:40PM +0530, Amit Kucheria wrote: > > On Fri, May 10, 2019 at 2:54 PM Sudeep Holla <sudeep.holla@xxxxxxx> wrote: > > > > > [...] > > > > > > > Yes entry-method="psci" is required as per DT binding but not checked > > > in code on arm64. We have CPU ops with idle enabled only for "psci", so > > > there's not need to check. > > > > I don't see it being checked on arm32 either. > > > > arm_cpuidle_get_ops in arch/arm/kernel/cpuidle.c checks the method, has > to match "psci" for drivers/firmware/psci.c to work on arm32 That is a check for the enable-method, not entry-method. We don't check for entry-method anywhere, AFAICT. > [...] > > > > > > > Why do you want to deprecated just because Linux kernel doesn't want to > > > use it. That's not a valid reason IMO. > > > > Fair enough. Just want to make sure that it isn't some vestigial > > property that was never used. Do you know if another OS is actually > > using it? > > > > Not that I am aware of. But Linux uses it on arm32, so it's not entirely > unused. entry-method is not read in Linux code (see above). > > > > Do we expect to support PSCI platforms that might have a different > > > > entry-method for idle states? > > > > > > Not on ARM64, but same DT bindings can be used for idle-states on > > > say RISC-V and have some value other than "psci". > > > > Both enable-method and entry-method properties are currently only used > > (and documented) for ARM platforms. Hence this discussion about > > deprecation of one of them. > > > > Yes, it's used on arm32 as mentioned above. Only enable-method is checked. > > > > Should I whip up a patch removing entry-method? Since we don't check > > > > for it today, it won't break the old DTs either. > > > > > > > > > > Nope, I don't think so. But if it's causing issues, we can look into it. > > > I don't want to restrict the use of the bindings for ARM/ARM64 or psci only. > > > > Only a couple of minor issues: > > 1. There is a trickle of DTs that need fixing up every now and then > > because they don't use entry-method in their idle-states node. Schema > > validation ought to fix that. > > I understand, scheme should fix it. This is not just restricted to this, > it's generic DT problem. So let's hope we get schema based validation soon. > > > 2. A property that isn't ready by any code is a bit confusing. Perhaps > > we can mention something to the effect in the documentation? > > > > Not entirely true. We have quite a lot of bindings that are added just > because downstream drivers use e.g. GPU and even standard ePAPR or DT > specification has lots of bindings which OS like Linux may choose > not to use at all. Same applies to ACPI, so I am not for removing bindings > just because there are no users in Linux. That is a fair point. But in those cases, the binding is probably used by another OS. entry-method seems to an example of one that isn't used by Linux or other OSes. Regards, Amit
