From mboxrd@z Thu Jan 1 00:00:00 1970 From: Philipp Zabel Subject: Re: [PATCH v7 2/5] ARM: imx6: gpc: Add PU power domain for GPU/VPU Date: Tue, 9 Sep 2014 22:49:38 +0200 Message-ID: <20140909204938.GA26440@pengutronix.de> References: <1409060791-23167-1-git-send-email-p.zabel@pengutronix.de> <1409060791-23167-3-git-send-email-p.zabel@pengutronix.de> <1410177246.3981.34.camel@paszta.hi.pengutronix.de> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: Sender: devicetree-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Ulf Hansson Cc: Philipp Zabel , Shawn Guo , Tomasz Figa , Rob Herring , Mark Rutland , Sascha Hauer , "linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org" , "devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" List-Id: devicetree@vger.kernel.org On Tue, Sep 09, 2014 at 09:01:08PM +0200, Ulf Hansson wrote: > [...] > > >> > + is_off = IS_ENABLED(CONFIG_PM_RUNTIME); > >> > + if (is_off) > >> > + imx6q_pm_pu_power_off(&imx6q_pu_domain.base); > >> > >> Could you elaborate why is_off depends on CONFIG_PM_RUNTIME? That > >> seems strange to me. :-) > >> > >> Additionally, I think it would be better to leave the domain "on" > >> state. Wouldn't that even be required for some drivers to be able to > >> succeed probing of these devices? > > > > The devices in the PU power domain are Vivante GPUs and the CODA Video > > Processing Unit. These are platform devices that don't need to be active > > to enumerate before being probed. The drivers support runtime PM, so if > > CONFIG_PM_RUNTIME is enabled, it is safe to disable the PU power domain > > on boot. The drivers will probe and request for the power domain to be > > enabled via runtime PM before accessing the hardware. > > > > If CONFIG_PM_RUNTIME is disabled, the power domain needs to stay enabled > > at all times. > > Hi Philipp, > > Thanks for your reply, that certainly made it clear on what you would > like to accomplish. > > Before discussing further consequences in genpd of this approach > (using IS_ENABLED(CONFIG_PM_RUNTIME)), I would be interested to see > how the runtime PM support is implemented for any of the drivers you > refer to. Do you mind pointing me to any of them? Of course, the CODA driver is at drivers/media/platform/coda.c in mainline kernels (moved to drivers/media/platform/coda-common.c in linux-next). regards Philipp -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html