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

[Jarkko Nikula]

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@xxxxxxxxxxxxxxx>
> > > ---
> > >    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);... }
      -> probe
  driver_bound -> BUS_NOTIFY_BOUND_DRIVER

>  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.
Sure.

--
Jarkko
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