From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jisheng Zhang Subject: Re: [PATCH] i2c: designware: separate ops for system_sleep_pm and runtime_pm Date: Tue, 19 May 2015 20:32:42 +0800 Message-ID: <20150519203242.74617ad6@xhacker> References: <1431693099-2292-1-git-send-email-jszhang@marvell.com> <20150518082823.GH1490@lahna.fi.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20150518082823.GH1490-3PARRvDOhMZrdx17CPfAsdBPR1lH4CV8@public.gmane.org> Sender: linux-i2c-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Mika Westerberg Cc: wsa-z923LK4zBo2bacvFa/9K2g@public.gmane.org, linux-i2c-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org List-Id: linux-i2c@vger.kernel.org Dear Mika, On Mon, 18 May 2015 11:28:23 +0300 Mika Westerberg wrote: > On Fri, May 15, 2015 at 08:31:39PM +0800, Jisheng Zhang wrote: > > Commit 1fc2fe204cb9 ("i2c: designware: Add runtime PM hooks") adds > > runtime pm support using the same ops for system sleep and runtime pm. > > When suspend to ram, the i2c host may have been runtime suspended, thus > > i2c_dw_disable() hangs. > > It hangs because it has already been powered off, right? Either be powered off or clock gated or even both. > > > This patch fixes this issue by separating ops for system sleep pm and > > runtime pm, and in the system suspend/resume path, runtime pm apis are > > used to ensure the device is at correct state. > > I can see that this fixes the issue with the platform driver (as the > platform bus core doesn't power on the device automatically as opposed > to other buses, like PCI). However, I'm thinking that can we do better > here. > > Instead of powering the device on again, can't we leave it in low power > state? Recently added 'dev->power.direct_complete' may be used to > achieve that, I think. how to handle runtime suspended via just being clock gated? Currently the only solution is using the runtime pm apis to ensure the device is in a working state during s2ram. What's your opinion? Thanks, Jisheng