From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757140AbaJHNsx (ORCPT ); Wed, 8 Oct 2014 09:48:53 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:46016 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756440AbaJHNrN (ORCPT ); Wed, 8 Oct 2014 09:47:13 -0400 Date: Wed, 8 Oct 2014 06:46:15 -0700 From: Greg KH To: Linus Walleij Cc: Doug Anderson , Thierry Reding , Mark Brown , Lee Jones , Chris Zhong , Heiko Stuebner , Sonny Rao , "linux-kernel@vger.kernel.org" Subject: Re: [RFC PATCH] drivers/pinctrl: Add the concept of an "init" state Message-ID: <20141008134615.GA6586@kroah.com> References: <1412713696-13343-1-git-send-email-dianders@chromium.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: 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 On Wed, Oct 08, 2014 at 11:00:11AM +0200, Linus Walleij wrote: > On Tue, Oct 7, 2014 at 10:28 PM, Doug Anderson wrote: > > > For pinctrl the "default" state is applied to pins before the driver's > > probe function is called. This is normally a sensible thing to do, > > but in some cases can cause problems. That's because the pins will > > change state before the driver is given a chance to program how those > > pins should behave. > > > > As an example you might have a regulator that is controlled by a PWM > > (output high = high voltage, output low = low voltage). The firmware > > might leave this pin as driven high. If we allow the driver core to > > reconfigure this pin as a PWM pin before the PWM's probe function runs > > then you might end up running at too low of a voltage while we probe. > > > > Let's introudce a new "init" state. If this is defined we'll set > > pinctrl to this state before probe and then "default" after probe > > (unless the driver explicitly changed states already). > > > > An alternative idea that was thought of was to use the pre-existing > > "sleep" or "idle" states and add a boolean property that we should > > start in that mode. This was not done because the "init" state is > > needed for correctness and those other states are only present (and > > only transitioned in to and out of) when (optional) power management > > is enabled. > > > > Signed-off-by: Doug Anderson > > I *like* this approach. A lot. > > It will come with DT bindings for free as it's just strings. > > > +++ b/drivers/base/dd.c > > @@ -308,6 +308,8 @@ static int really_probe(struct device *dev, struct device_driver *drv) > > goto probe_failed; > > } > > > > + pinctrl_init_done(dev); > > We will need Greg's ACK for this oneliner. As much as I hate subsystem-specific code in the driver core, I guess I let this happen before, so I can't object here :) Acked-by: Greg Kroah-Hartman