linux-kernel - Re: [RESEND PATCH 1/2] spi: rockchip: Convert to late and early system PM callbacks

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Message-ID: <20171013183048.dg6wsabnz7qiviwy@dtor-ws>
Date:   Fri, 13 Oct 2017 11:30:48 -0700
From:   Dmitry Torokhov <dmitry.torokhov@...il.com>
To:     jeffy <jeffy.chen@...k-chips.com>
Cc:     Mark Brown <broonie@...nel.org>,
        Brian Norris <briannorris@...omium.org>,
        Doug Anderson <dianders@...omium.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Heiko Stuebner <heiko@...ech.de>,
        linux-spi <linux-spi@...r.kernel.org>,
        "open list:ARM/Rockchip SoC..." <linux-rockchip@...ts.infradead.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [RESEND PATCH 1/2] spi: rockchip: Convert to late and early
 system PM callbacks

On Sat, Oct 14, 2017 at 02:25:48AM +0800, jeffy wrote:
> On 10/14/2017 02:19 AM, jeffy wrote:
> > 
> > 
> > it looks like the suspend sequence depends on the dt node sequence, and
> > we are putting display-subsystem dt node above spi dt node, so it would
> > be earlier in the device list, then got suspended later than spi device.
> > 
> > the pwm backlight and cros_ec_spi pwm are very interesting, not only
> > about suspend dependency... if we unbind cros_ec_spi pwm, the pwm
> > backlight would still hold a reference to it, and crash the kernel later.
> 
> or maybe we should move device_pm_add() from device_add() to driver_bound()?

You do not necessarily need to have a driver to power the dveice on and
off.

-- 
Dmitry