From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alex Courbot Subject: Re: [PATCHv9 1/3] Runtime Interpreted Power Sequences Date: Wed, 21 Nov 2012 10:56:36 +0900 Message-ID: <4316169.5QXVzv7peZ@percival> References: <1353149747-31871-1-git-send-email-acourbot@nvidia.com> <1353149747-31871-2-git-send-email-acourbot@nvidia.com> <50AB9832.90709@ti.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7Bit Return-path: In-Reply-To: <50AB9832.90709-l0cyMroinI0@public.gmane.org> Sender: linux-tegra-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Tomi Valkeinen Cc: Anton Vorontsov , Stephen Warren , Thierry Reding , Mark Zhang , Grant Likely , Rob Herring , Mark Brown , David Woodhouse , Arnd Bergmann , "linux-tegra-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , "linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org" , "linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , "linux-fbdev-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , "devicetree-discuss-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org" , "linux-pm-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , Alexandre Courbot List-Id: linux-pm@vger.kernel.org Hi Tomi, On Tuesday 20 November 2012 22:48:18 Tomi Valkeinen wrote: > I guess there's a reason, but the above looks a bit inconsistent. For > gpio you define the gpio resource inside the step. For power and pwm the > resource is defined before the steps. Why wouldn't "pwm = <&pwm 2 > 5000000>;" work in step2? That's mostly a framework issue. Most frameworks do not export a function that allow to dereference a phandle - they expect resources to be declared right under the device node and accessed by name through foo_get(device, name). So using phandles in power sequences would require to export these additional functions and also opens the door to some inconsistencies - for instance, your PWM phandle could be referenced a second time in the sequence with a different period - how do you know that these are actually referring the same PWM device? > > +When a power sequence is run, its steps is executed one after the other > > until +one step fails or the end of the sequence is reached. > > The document doesn't give any hint of what the driver should do if > running the power sequence fails. Run the "opposite" power sequence? > Will that work for all resources? I'm mainly thinking of a case where > each enable of the resource should be matched by a disable, i.e. you > can't call disable if no enable was called. We discussed that issue already (around v5 I think) and the conclusion was that it should be up to the driver. When we simply enable/disable resources it is easy to revert, but in the future non-boolean properties will likely be introduced, and these cannot easily be reverted. Moreover some drivers might have more complex recovery needs. This deserves more discussion I think, as I'd like to have some "generic" recovery mechanism that covers most of the cases. Alex.