From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: ARC-Seal: i=1; a=rsa-sha256; t=1525710881; cv=none; d=google.com; s=arc-20160816; b=sszhVWiEmB6jUc+Ajhz0kjzCdxPQMlrdeDf2KaZbuo+Pa5XrEnTQpl0LI3vH+jEzwk kz3myK/hqOjcHWTxaN5BaLya/siTV07Th4NdW02OkhUvYgyN3au2VSUAIIQCBw2DHQUO hhzqoctbvYwGldv2gKQXFg/HdJqZ63w2EWQ/QogCkXS+pFXalytysuP20ICDEFkPz6dr 95KbZlbADhwPmV2vtctIKyJYPC6g7Gv9+N+aVtLc4SkxL3sodJp/CLiPennLSV7toguf BK9jvRyLh1/i628RzOwdJ3IlrfTSaQz8BkQC2IK37JFP5xiyXhDn8e+KJ6+a6N/9K7WI hopw== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=user-agent:in-reply-to:content-disposition:mime-version:references :message-id:subject:cc:to:from:date:sender:dkim-signature :arc-authentication-results; bh=qEKueACvwjZr6nTROyIxt34gKgL4Oa/gNPjKkUPYbkM=; b=YzlA5zXHZZIa9A4kGuK/0y+VTDSwtPfTVThfLtA5l++p/zoAJpU8k3nhVTq8/xBwso jJfRDpup7oIcNUhUInhzEgsmGtLHOmQ37hofEscZMZAjGjw/R2+zGsnSd5+d/aFC4VfL uUZYTkq0BK25jPKKteQ2fyXwdOz2mhjrDJR41zMy73wq6p28fEV7/s8VA7kY2hQi743N nQoXtyBWLU6Ea/HNvjZ9KxbM5y8Mgg2NACM0YQemtgN43JtZAL1TUnzqO4NCDC1ZWkUD nP2PH43wFrYFFdCEkxBSdA4TrNaRmwl57Hgr9JXIXy82omQAFokERDngAvjYq+HzNMoP 5V6w== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b=MDq9Nwei; spf=pass (google.com: domain of jhovold@gmail.com designates 209.85.220.41 as permitted sender) smtp.mailfrom=jhovold@gmail.com; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=kernel.org Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b=MDq9Nwei; spf=pass (google.com: domain of jhovold@gmail.com designates 209.85.220.41 as permitted sender) smtp.mailfrom=jhovold@gmail.com; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=kernel.org X-Google-Smtp-Source: AB8JxZqqWYS9duf1DwmvrS5GvA8f5tM9iwEuiH/iVq/2VLPTw7MXbFnmeuOx0r1NGilmxiVda1uknA== Sender: Johan Hovold Date: Mon, 7 May 2018 18:34:39 +0200 From: Johan Hovold To: Tony Lindgren Cc: Johan Hovold , Sebastian Reichel , "H. Nikolaus Schaller" , Andreas Kemnade , Mark Rutland , Arnd Bergmann , Pavel Machek , "linux-kernel@vger.kernel.org" , "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" , Greg Kroah-Hartman , Rob Herring Subject: Re: [PATCH 4/7] dt-bindings: gnss: add u-blox binding Message-ID: <20180507163439.GV2285@localhost> References: <20180426091018.GU4615@localhost> <20180502081637.GE2285@localhost> <5242FCAD-3139-4A9C-B9FA-7BBAA0E6AE57@goldelico.com> <20180503205037.7be552c1@aktux> <44A0BC7C-67C7-4116-849F-90FF7CF2B1F0@goldelico.com> <20180504114213.3xlzqxe74n55tk5s@earth.universe> <20180507100135.GS2285@localhost> <20180507154515.GP98604@atomide.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180507154515.GP98604@atomide.com> User-Agent: Mutt/1.9.5 (2018-04-13) X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: =?utf-8?q?1598647064088300079?= X-GMAIL-MSGID: =?utf-8?q?1599823813194764143?= X-Mailing-List: linux-kernel@vger.kernel.org List-ID: On Mon, May 07, 2018 at 08:45:15AM -0700, Tony Lindgren wrote: > Hi, > > * Johan Hovold [180507 03:03]: > > On Fri, May 04, 2018 at 01:42:13PM +0200, Sebastian Reichel wrote: > > > > > Having said all of this, serdev does not yet support runtime PM (at > > > all). Tony is currently looking into it. Fortunately serdev allows > > > us to enable runtime PM by default (once implemented), since we know > > > the remote side and can (hopefully) avoid losing characters (i.e. > > > with sideband wakeup gpios). > > > > I'm not sure we want generic runtime-pm support for the controllers in > > the sense that the slave device state is always reflected by the serial > > controller. Similar as for i2c and spi, we really only want to keep the > > controller active when we are doing I/O, but we may want to keep a > > client active for longer. > > Yeah i2c seems to do the right thing where the bus takes care > of runtime PM. Yeah, but since serial is async in contrast to i2c/spi, we may not be able to push this entirely into core. The serdev drivers may need to indicate when they expect or need to do I/O by opening and closing the port. And this is how I implemented these first couple of gnss drivers. Also note that most serial driver do not do runtime pm while the port is open (as OMAP does), and doing so also has the drawbacks of lost characters etc. as Sebastian mentioned. > > Take the u-blox driver in this series for example. As I'm using runtime > > PM to manage device power, user-space can chose to prevent the receiver > > from runtime suspending in order to avoid lengthy (re-)acquisition times > > in setups without a backup battery (by means of the power/control > > attribute). > > Sorry I don't seem to have that one, care to paste the subject > line of that patch? "[PATCH 5/7] gnss: add driver for u-blox receivers" https://lkml.kernel.org/r/20180424163458.11947-6-johan@kernel.org > > Note that serdev not enabling runtime pm for controllers is roughly > > equivalent to setting the .ignore_children flag, which is what we do for > > i2c and spi controller, and possibly what we want here too. > > We currently don't idle serdev at all even if not in use. What > I noticed is if I have these in my .config: > > CONFIG_SERIAL_DEV_BUS=y > CONFIG_SERIAL_DEV_CTRL_TTYPORT=y > > And no hci_serdev.ko driver loaded, then the 8250 port still stays > active and there are no sysfs entries to idle it. Sounds like the 8250_omap driver is doing something funky. Why would there not be any sysfs attributes to control runtime pm? > Are you seeing this with your series? I'm using omap-serial (on BBB) and like 8250_omap, the driver disables runtime pm at probe by setting a negative autosuspend timeout. Changing this through sysfs causes the serial controller to runtime suspend, but something is not right in my setup as it doesn't wake up on incoming data. I'd say the omap drivers are broken; the controller should definitely idle when the port is closed (whether using serdev or not) without having to fiddle with sysfs. Thanks, Johan