From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jan Kiszka Date: Fri, 28 Nov 2014 09:52:02 +0100 Subject: [U-Boot] ARM: PSCI 0.1 vs 0.2 In-Reply-To: <5460BF71.8010508@arm.com> References: <5460B4B5.2060602@siemens.com> <5460B8E8.9070706@arm.com> <5460BCE0.2020301@siemens.com> <5460BF71.8010508@arm.com> Message-ID: <547837B2.1020700@web.de> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: u-boot@lists.denx.de On 2014-11-10 14:36, Marc Zyngier wrote: > On 10/11/14 13:25, Jan Kiszka wrote: >> On 2014-11-10 14:08, Marc Zyngier wrote: >>> On 10/11/14 12:51, Jan Kiszka wrote: >>>> Hi Marc, >>>> >>>> what is the motivation to expose a PSCI 0.1 interface in U-boot, instead >>>> of 0.2? Support for preexisting users of 0.1? The kernel seems to be >>>> happy with both, and I'm now wondering if we should actually add the >>>> legacy version to Jailhouse as well (I hope we can avoid this). >>> >>> The initial rational was simple: at the time this code was written, the >>> 0.2 spec still in review, and nobody was implementing it. Supporting 0.1 >>> was the only viable use-case. >>> >>>> Still studying the logic: Is it possible to provide both interfaces, and >>>> would it make sense? >>> >>> Supporting both is very easy. Just output the 0.2 function numbers that >>> actually make sense for 0.1 and have both compatible strings. >> >> Ah, cool - parameters and return values of, say, CPU_ON/OFF are >> compatible across both versions? > > That was the idea of the spec (broadly compatible across revisions...). There is one major problem with v0.2, though, and I bet this also applies to the ARMv8 implementation: v0.2 mandates that the firmware provides SYSTEM_RESET - that's rather simple - and SYSTEM_OFF. The latter seems non-trivial for the sunxi as the power controller is attached via i2c. I guess that will be quite a bit of code in the PSCI monitor for a feature that already works fine for Linux with v0.1. Or am I missing something? Jan -------------- next part -------------- A non-text attachment was scrubbed... Name: signature.asc Type: application/pgp-signature Size: 198 bytes Desc: OpenPGP digital signature URL: