linux-kernel - Re: [PATCH 0/7] Implement generic regulator constraints parsing for ACPI and OF

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Message-ID: <20170125203907.df2elgy3ao2o2e3h@sirena.org.uk>
Date:   Wed, 25 Jan 2017 20:39:07 +0000
From:   Mark Brown <broonie@...nel.org>
To:     Dmitry Torokhov <dmitry.torokhov@...il.com>
Cc:     Mark Rutland <mark.rutland@....com>,
        Furquan Shaikh <furquan@...omium.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        "Rafael J . Wysocki" <rjw@...ysocki.net>,
        Liam Girdwood <lgirdwood@...il.com>,
        Tony Lindgren <tony@...mide.com>, Len Brown <lenb@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Hanjun Guo <hanjun.guo@...aro.org>,
        Will Deacon <will.deacon@....com>,
        Rob Herring <robh@...nel.org>,
        Sathyanarayana Nujella <sathyanarayana.nujella@...el.com>,
        Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        Adam Thomson <Adam.Thomson.Opensource@...semi.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        Alexandre Courbot <gnurou@...il.com>,
        linux-gpio@...r.kernel.org,
        ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux OMAP Mailing List <linux-omap@...r.kernel.org>,
        Aaron Durbin <adurbin@...omium.org>, dlaurie@...omium.org
Subject: Re: [PATCH 0/7] Implement generic regulator constraints parsing for
 ACPI and OF

On Wed, Jan 25, 2017 at 11:27:11AM -0800, Dmitry Torokhov wrote:

> For the record, the main issue for the drivers, which is being solved by
> exposing power supplies to the driver, is the following:

> 1. We suspend the device. Since there is no regulators the driver
> assumes that it will retain it's state upon resume

That's *not* a sensible thing for drivers to assume regardless of the
presence or absence of explicitly controlled regulators, that just seems
like a plain old driver bug.  Even if there are regulators that doesn't
mean there isn't a suspend mode configuration that disables those
regulators.

> I would really hate to go through _every_ driver and add the following
> code to the resume path:
> 
> #if IS_ENABLED(CONFIG_ACPI)
> 	if (acpi_device_was_powered_off_between_suspend_and_now(dev)) {
> 		completely_reinitialize_device(dev);
> 	}
> #endif

That's not an ACPI thing, unless the device thinks it's actively
providing a wakeup source then if the system suspends the driver should
not be surprised to have power pulled - that's pretty normal.  If the
driver is a wakeup source then it's a bit different.

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