Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756153AbcKKMBT (ORCPT ); Fri, 11 Nov 2016 07:01:19 -0500 Received: from atrey.karlin.mff.cuni.cz ([195.113.26.193]:51961 "EHLO atrey.karlin.mff.cuni.cz" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754170AbcKKMBR (ORCPT ); Fri, 11 Nov 2016 07:01:17 -0500 Date: Fri, 11 Nov 2016 13:01:14 +0100 From: Pavel Machek To: Jacek Anaszewski Cc: Tony Lindgren , Jacek Anaszewski , Hans de Goede , linux-leds@vger.kernel.org, linux-omap@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Darren Hart Subject: Re: PM regression with LED changes in next-20161109 Message-ID: <20161111120114.GA1076@amd> References: <20161109192301.GS26979@atomide.com> <28234714-3994-6747-9cf8-1ff0b3257f7a@gmail.com> <5bd5333e-0dbb-6333-0a48-ca4d3a990f9c@samsung.com> <20161110162925.GA28832@amd> <20161110175537.GF27724@atomide.com> <20161110202910.GE28832@amd> <80b645e7-c3fa-8001-d9b1-c3c8c40394fd@gmail.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="qDbXVdCdHGoSgWSk" Content-Disposition: inline In-Reply-To: <80b645e7-c3fa-8001-d9b1-c3c8c40394fd@gmail.com> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3044 Lines: 93 --qDbXVdCdHGoSgWSk Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Thu 2016-11-10 22:34:07, Jacek Anaszewski wrote: > Hi, >=20 > On 11/10/2016 09:29 PM, Pavel Machek wrote: > >On Thu 2016-11-10 10:55:37, Tony Lindgren wrote: > >>* Pavel Machek [161110 09:29]: > >>>Hi! > >>> > >>>>>>>Looks like commit 883d32ce3385 ("leds: core: Add support for poll(= )ing > >>>>>>>the sysfs brightness attr for changes.") breaks runtime PM for me. > >>>>>>> > >>>>>>>On my omap dm3730 based test system, idle power consumption is ove= r 70 > >>>>>>>times higher now with this patch! It goes from about 6mW for the c= ore > >>>>>>>system to over 440mW during idle meaning there's some busy timer n= ow > >>>>>>>active. > >>>>>>> > >>>>>>>Reverting this patch fixes the issue. Any ideas? > >>> > >>>Are you using any LED that toggles with high frequency? Like perhaps > >>>LED that is lit when CPU is active? > >> > >>Yeah one of them seems to have cpu0 as the default trigger. > > > >Aha. Its quite obvious we don't want to notify sysfs each time that > >one is toggled, right? > > > >IMO brightness should display max brightness for the trigger, as Hans > >suggested, anything else is madness for trigger such as cpu activity. >=20 > Are you suggesting that we should revert changes introduced > by below patch? >=20 > commit 29d76dfa29fe22583aefddccda0bc56aa81035dc > Author: Henrique de Moraes Holschuh > Date: Tue Mar 18 09:47:48 2008 +0000 >=20 > leds: Add support to leds with readable status >=20 > Some led hardware allows drivers to query the led state, and this pat= ch > adds a hook to let the led class take advantage of that information w= hen > available. >=20 > Without this functionality, when access to the led hardware is not > exclusive (i.e. firmware or hardware might change its state behind the > kernel's back), reality goes out of sync with the led class' idea of > what > the led is doing, which is annoying at best. Hmm. So userland can read the LED state, and it can get _some_ value back, but it can not know if it is current state or not. I don't think that's a good interface. I see it is from 2008... is someone using it? Maybe it is too late for revert. But I'd certainly not extend it with poll. IMO reading/polling should only be available with some triggers. It does not make sense with "CPU load" trigger. It makes sense with "keyboard light changeable by hardware" trigger. Best regards, =09 Pavel --=20 (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blo= g.html --qDbXVdCdHGoSgWSk Content-Type: application/pgp-signature; name="signature.asc" Content-Description: Digital signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 iEYEARECAAYFAlglswkACgkQMOfwapXb+vI7ZACeO3OyBWqqaUCGlbfzN0DbHDEJ MmUAoL05Ct9aqRIDEADk7n624C/yuPOx =8sPW -----END PGP SIGNATURE----- --qDbXVdCdHGoSgWSk--