linux-kernel - Re: [PATCH v2 2/7] ACPI / LPSS: allow to use specific PM domain during ->probe()

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Date:	Fri, 27 Nov 2015 11:56:13 +0200
From:	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:	"Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:	Jarkko Nikula <jarkko.nikula@...ux.intel.com>,
	linux-acpi@...r.kernel.org, Vinod Koul <vinod.koul@...el.com>,
	dmaengine@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-kernel@...r.kernel.org,
	Mika Westerberg <mika.westerberg@...ux.intel.com>
Subject: Re: [PATCH v2 2/7] ACPI / LPSS: allow to use specific PM domain
 during ->probe()

On Fri, 2015-11-27 at 00:15 +0100, Rafael J. Wysocki wrote:
> On Thursday, November 26, 2015 06:45:17 PM Andy Shevchenko wrote:
> > On Thu, 2015-11-26 at 18:30 +0200, Jarkko Nikula wrote:
> > > On 11/26/2015 05:19 PM, Andy Shevchenko wrote:
> > > > This is an amendment to previously pushed commit 01ac170ba29a
> > > > (ACPI
> > > > / LPSS:
> > > > allow to use specific PM domain during ->probe()). We can't
> > > > assign
> > > > anything to
> > > > the platform device on ADD_DEVICE stage since it might be
> > > > changed
> > > > during
> > > > unbound / bind cycle.
> > > > 
> > > > Signed-off-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.c
> > > > om>
> > > > ---
> > > >   drivers/acpi/acpi_lpss.c | 9 +++++++--
> > > >   1 file changed, 7 insertions(+), 2 deletions(-)
> > > > 
> > > > diff --git a/drivers/acpi/acpi_lpss.c
> > > > b/drivers/acpi/acpi_lpss.c
> > > > index f9e0d09..e840229 100644
> > > > --- a/drivers/acpi/acpi_lpss.c
> > > > +++ b/drivers/acpi/acpi_lpss.c
> > > > @@ -705,8 +705,14 @@ static int
> > > > acpi_lpss_platform_notify(struct
> > > > notifier_block *nb,
> > > >   	}
> > > > 
> > > >   	switch (action) {
> > > > -	case BUS_NOTIFY_ADD_DEVICE:
> > > > +	case BUS_NOTIFY_BIND_DRIVER:
> > > >   		pdev->dev.pm_domain = &acpi_lpss_pm_domain;
> > > > +		break;
> > > > +	case BUS_NOTIFY_BIND_DRIVER_ERROR:
> > > > +	case BUS_NOTIFY_UNBOUND_DRIVER:
> > > > +		pdev->dev.pm_domain = NULL;
> > > > +		break;
> > > > +	case BUS_NOTIFY_ADD_DEVICE:
> > > 
> > > This won't fix like revert of original commit does.
> 
> Which commit exactly are you talking about, for reference?

commit 01ac170ba29a9903ee590e1ef2d8e6b27b49a16c
Author: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Date:   Wed Nov 5 18:34:46 2014 +0200

    ACPI / LPSS: allow to use specific PM domain during ->probe()
    

> > > Primary problem here 
> > > is that there is no explicit power on at all during LPSS device
> > > probe
> > > because dev->pm_domain is set before probing.
> > 
> > And we can't do this as in very original code of acpi_lpss.c since
> > DMA
> > has to be sure it's powered on while probing. We could guarantee
> > this
> > only in case when PM domain is assigned already and we do our quirk
> > for
> > it.
> > 
> > From my point of view we have to fix hang first since it's most
> > painful
> > case for users and their experience. Though I'm open to any better
> > solution if you have any in mind.
> > 
> > > 
> > > driver_probe_device
> > >    platform_drv_prove
> > >      dev_pm_domain_attach
> > >        acpi_dev_pm_attach
> > >          returns instantly because of dev->pm_domain is set
> 
> This looks like a candidate for the new PM domain callbacks,
> ->activate and
> ->dismiss.
> 
> ->activate() is called before the probe, so it may power up things.
> 
> ->dismiss() in turn is called in the failed probe case, so it can do
> the
> cleanup.
> 
> Have you considered using these?

Thanks for the hint. We will check this.

-- 
Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Intel Finland Oy

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