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 12:01:25 +0200
From:	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:	Jarkko Nikula <jarkko.nikula@...ux.intel.com>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	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 09:05 +0200, Jarkko Nikula wrote:
> On 11/26/2015 06:45 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. 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.
> > 
> I'm not sure do I follow here. Is the power on chain different for
> LPSS 
> DMA because setting the domain at BIND stage prevents the call to 
> acpi_dev_pm_full_power() before driver probe? See below.
> 
> driver_probe_device
>    really_probe
>      driver_sysfs_add -> BUS_NOTIFY_BIND_DRIVER
>      -> platform_drv_prove
>        dev_pm_domain_attach
>          acpi_dev_pm_attach
>            if (dev->pm_domain) return -EEXIST;
>            ...
>            if (power_on) { acpi_dev_pm_full_power(adev);... }

And how exactly does it enable a power on DMA controller that doesn't
have _PS0 / _PS3 / _PSC methods?

Maybe I missed something obvious.

>        -> probe
>    driver_bound -> BUS_NOTIFY_BOUND_DRIVER


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

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