Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932575Ab2EJOLV (ORCPT ); Thu, 10 May 2012 10:11:21 -0400 Received: from mail-yx0-f174.google.com ([209.85.213.174]:62925 "EHLO mail-yx0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751972Ab2EJOLT convert rfc822-to-8bit (ORCPT ); Thu, 10 May 2012 10:11:19 -0400 MIME-Version: 1.0 In-Reply-To: <20120510124130.GS27341@pengutronix.de> References: <1336425407-20308-1-git-send-email-rob.lee@linaro.org> <1336425407-20308-3-git-send-email-rob.lee@linaro.org> <20120509080214.GJ27341@pengutronix.de> <20120510124130.GS27341@pengutronix.de> From: Rob Lee Date: Thu, 10 May 2012 09:10:54 -0500 Message-ID: Subject: Re: [PATCH v3 2/3] ARM: imx: Add imx5 cpuidle driver To: Sascha Hauer Cc: kernel@pengutronix.de, shawn.guo@linaro.org, amit.kucheria@linaro.org, daniel.lezcano@linaro.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linaro-dev@lists.linaro.org, patches@linaro.org, jj@chaosbits.net Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2651 Lines: 63 On Thu, May 10, 2012 at 7:41 AM, Sascha Hauer wrote: > On Wed, May 09, 2012 at 09:27:02AM -0500, Rob Lee wrote: >> Sascha, >> >> > >> > This clk_get should go away here and be moved somewhere to >> > initialization. Also, if getting this clock fails we can still >> > do regular cpu_do_idle. Additionally, if clk_get fails, we'll >> > have a ERR_PTR value in gpc_dvfs_clk in which case the >> > gpc_dvfs_clk == NULL won't trigger next time you are here and >> > then you'll enable a nonexisting clock below. >> > >> >> Agree. ?I'd prefer to enable this clock during intialization and just >> leave it running. ?It is supposed to be a very low power clock and I >> couldn't measuring any power difference with and without it being >> enabled > > Ok, even better. > >> > >> > I wonder why you don't add the default ARM_CPUIDLE_WFI_STATE_PWR state. >> > The above is something different, right? It has a greater exit latency >> > than ARM_CPUIDLE_WFI_STATE_PWR, so why don't we add it here aswell? >> >> Yes and no. ?Yes this is a different state but no, it doesn't have a >> significantly greater exit latency, or at least a large enough exit >> latency to warrant an extra state in my opinion. ?According to the >> i.MX5 documentation, the extra exit time beyond basic WFI required for >> the ?"WAIT_UNCLOCKED_POWER_OFF" state is 500ns (this is due to a >> difference in i.MX5 hardware implementation compared to all other ARM >> platforms). ?In reality, it did require a few more microseconds to >> perform in my testing just based on the extra register writes in >> mx5_cpu_lp_set(). ?I'd like to clean up mx5_cpu_lp_set() and add a >> global variable to track the previous state and to just exit out if >> the new state is the same as the old. > > Do you think it's worth it? You buy skipping the read with an additional > test. > I'll run some tests to check. Thanks, Rob >> I could do this cleanup as part of this patchset if you prefer that. > > Yes please. Cleanups before adding new features is always a good reason > to apply a patch series ;) > > Sascha > > -- > Pengutronix e.K. ? ? ? ? ? ? ? ? ? ? ? ? ? | ? ? ? ? ? ? ? ? ? ? ? ? ? ? | > Industrial Linux Solutions ? ? ? ? ? ? ? ? | http://www.pengutronix.de/ ?| > Peiner Str. 6-8, 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 ? ?| > Amtsgericht Hildesheim, HRA 2686 ? ? ? ? ? | Fax: ? +49-5121-206917-5555 | -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/