From mboxrd@z Thu Jan 1 00:00:00 1970 From: Uwe =?iso-8859-1?Q?Kleine-K=F6nig?= Subject: Re: [Patch V7] i2c: imx: add runtime pm support to improve the performance Date: Mon, 7 Sep 2015 23:18:14 +0200 Message-ID: <20150907211814.GI14598@pengutronix.de> References: <1441006353-874-1-git-send-email-b54642@freescale.com> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: Content-Disposition: inline In-Reply-To: <1441006353-874-1-git-send-email-b54642-KZfg59tc24xl57MIdRCFDg@public.gmane.org> Sender: linux-i2c-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Gao Pan Cc: wsa-z923LK4zBo2bacvFa/9K2g@public.gmane.org, linux-i2c-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, B20596-KZfg59tc24xl57MIdRCFDg@public.gmane.org, b38611-KZfg59tc24xl57MIdRCFDg@public.gmane.org, kernel-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org, hkallweit1-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org List-Id: linux-i2c@vger.kernel.org Hello, On Mon, Aug 31, 2015 at 03:32:33PM +0800, Gao Pan wrote: > In our former i2c driver, i2c clk is enabled and disabled in > xfer function, which contributes to power saving. However, > the clk enable process brings a busy wait delay until the core > is stable. As a result, the performance is sacrificed. >=20 > To weigh the power consumption and i2c bus performance, runtime > pm is the good solution for it. The clk is enabled when a i2c > transfer starts, and disabled after a specifically defined delay. >=20 > Without the patch the test case (many eeprom reads) executes with app= rox: > real 1m7.735s > user 0m0.488s > sys 0m20.040s >=20 > With the patch the same test case (many eeprom reads) executes with a= pprox: > real 0m54.241s > user 0m0.440s > sys 0m5.920s >=20 > Signed-off-by: Fugang Duan > Signed-off-by: Gao Pan > [wsa: fixed some indentation] > Signed-off-by: Wolfram Sang Hmm, why does this already have a S-o-b from Wolfram? Other than that I don't have any caveats to enter any more, but given that I don't have much clue about runtime pm this doesn't mean much. Best regards Uwe --=20 Pengutronix e.K. | Uwe Kleine-K=F6nig = | Industrial Linux Solutions | http://www.pengutronix.de/= |