From mboxrd@z Thu Jan  1 00:00:00 1970
From: Tony Lindgren <tony@atomide.com>
Subject: Re: [PATCH 4/7] dt-bindings: gnss: add u-blox binding
Date: Mon, 7 May 2018 08:45:15 -0700
Message-ID: <20180507154515.GP98604@atomide.com>
References: <20180424163458.11947-5-johan@kernel.org>
 <CAL_Jsq+mCp=geT8t_j+0fuTxAB7C9RYn6pESRpLc2GH273fM1Q@mail.gmail.com>
 <20180426091018.GU4615@localhost>
 <CAL_JsqK=xQBx2YCd0kDP0zLn_LAZb6Mi5UfSTQf2soooVz2unQ@mail.gmail.com>
 <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>
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Return-path: <linux-kernel-owner@vger.kernel.org>
Content-Disposition: inline
In-Reply-To: <20180507100135.GS2285@localhost>
Sender: linux-kernel-owner@vger.kernel.org
To: Johan Hovold <johan@kernel.org>
Cc: Sebastian Reichel <sre@kernel.org>, "H. Nikolaus Schaller" <hns@goldelico.com>, Andreas Kemnade <andreas@kemnade.info>, Mark Rutland <mark.rutland@arm.com>, Arnd Bergmann <arnd@arndb.de>, Pavel Machek <pavel@ucw.cz>, "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>, "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" <devicetree@vger.kernel.org>, Greg Kroah-Hartman <gregkh@linuxfoundation.org>, Rob Herring <robh+dt@kernel.org>
List-Id: devicetree@vger.kernel.org

Hi,

* Johan Hovold <johan@kernel.org> [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.

> 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?

> 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.

Are you seeing this with your series?

Regards,

Tony