linux-kernel - Re: [PATCH v4 3/8] Driver core: wakeup the parent device before trying probe

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Date:	Mon, 15 Jun 2015 13:50:34 +0200
From:	"Rafael J. Wysocki" <rafael@...nel.org>
To:	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:	"Rafael J . Wysocki" <rjw@...ysocki.net>,
	ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Vinod Koul <vinod.koul@...el.com>,
	Lee Jones <lee.jones@...aro.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Mika Westerberg <mika.westerberg@...ux.intel.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	dmaengine@...r.kernel.org,
	Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
	Jarkko Nikula <jarkko.nikula@...ux.intel.com>,
	"Wysocki, Rafael J" <rafael.j.wysocki@...el.com>,
	Mike Turquette <mturquette@...aro.org>
Subject: Re: [PATCH v4 3/8] Driver core: wakeup the parent device before
 trying probe

On Mon, Jun 15, 2015 at 11:57 AM, Andy Shevchenko
<andriy.shevchenko@...ux.intel.com> wrote:
> From: "Rafael J. Wysocki" <rjw@...ysocki.net>
>
> If the parent is still suspended when driver probe is
> attempted, the result may be failure.
>
> For example, if the parent is a PCI MFD device that has been
> suspended when we try to probe our device, any register
> reads will return 0xffffffff.
>
> To fix the problem, making sure the parent is always awake
> before attempting driver probe.
>
> Signed-off-by: Heikki Krogerus <heikki.krogerus@...ux.intel.com>
> Signed-off-by: Rafael J. Wysocki <rjw@...ysocki.net>

Please use my Intel sign-off with this one:

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>

> Signed-off-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
> ---
>  drivers/base/dd.c | 14 ++++++++++++++
>  1 file changed, 14 insertions(+)
>
> diff --git a/drivers/base/dd.c b/drivers/base/dd.c
> index e843fdb..c4c1eaf 100644
> --- a/drivers/base/dd.c
> +++ b/drivers/base/dd.c
> @@ -399,6 +399,8 @@ EXPORT_SYMBOL_GPL(wait_for_device_probe);
>   *
>   * This function must be called with @dev lock held.  When called for a
>   * USB interface, @dev->parent lock must be held as well.
> + *
> + * If the device has a parent, runtime-resume the parent before driver probing.
>   */
>  int driver_probe_device(struct device_driver *drv, struct device *dev)
>  {
> @@ -410,10 +412,16 @@ int driver_probe_device(struct device_driver *drv, struct device *dev)
>         pr_debug("bus: '%s': %s: matched device %s with driver %s\n",
>                  drv->bus->name, __func__, dev_name(dev), drv->name);
>
> +       if (dev->parent)
> +               pm_runtime_get_sync(dev->parent);
> +
>         pm_runtime_barrier(dev);
>         ret = really_probe(dev, drv);
>         pm_request_idle(dev);
>
> +       if (dev->parent)
> +               pm_runtime_put(dev->parent);
> +
>         return ret;
>  }
>
> @@ -459,8 +467,14 @@ int device_attach(struct device *dev)
>                         ret = 0;
>                 }
>         } else {
> +               if (dev->parent)
> +                       pm_runtime_get_sync(dev->parent);
> +
>                 ret = bus_for_each_drv(dev->bus, NULL, dev, __device_attach);
>                 pm_request_idle(dev);
> +
> +               if (dev->parent)
> +                       pm_runtime_put(dev->parent);
>         }
>  out_unlock:
>         device_unlock(dev);
> --
> 2.1.4
>
> --
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