linux-kernel - Re: [PATCH v6 3/8] Driver core: wakeup the parent device before trying probe

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Date:	Tue, 28 Jul 2015 08:47:43 +0100
From:	Lee Jones <lee.jones@...aro.org>
To:	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:	linux-acpi@...r.kernel.org, linux-pm@...r.kernel.org,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Vinod Koul <vinod.koul@...el.com>,
	Mika Westerberg <mika.westerberg@...ux.intel.com>,
	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>,
	mturquette@...libre.com, sboyd@...eaurora.org
Subject: Re: [PATCH v6 3/8] Driver core: wakeup the parent device before
 trying probe

On Mon, 27 Jul 2015, Andy Shevchenko wrote:

> From: "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>
> 
> 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 <rafael.j.wysocki@...el.com>
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
> ---
>  drivers/base/dd.c | 20 ++++++++++++++++++++
>  1 file changed, 20 insertions(+)

Applied, thanks.  Pull request to follow.

> diff --git a/drivers/base/dd.c b/drivers/base/dd.c
> index a638bbb..2d6df1d 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;
>  }
>  
> @@ -507,11 +515,17 @@ static void __device_attach_async_helper(void *_dev, async_cookie_t cookie)
>  
>  	device_lock(dev);
>  
> +	if (dev->parent)
> +		pm_runtime_get_sync(dev->parent);
> +
>  	bus_for_each_drv(dev->bus, NULL, &data, __device_attach_driver);
>  	dev_dbg(dev, "async probe completed\n");
>  
>  	pm_request_idle(dev);
>  
> +	if (dev->parent)
> +		pm_runtime_put(dev->parent);
> +
>  	device_unlock(dev);
>  
>  	put_device(dev);
> @@ -541,6 +555,9 @@ static int __device_attach(struct device *dev, bool allow_async)
>  			.want_async = false,
>  		};
>  
> +		if (dev->parent)
> +			pm_runtime_get_sync(dev->parent);
> +
>  		ret = bus_for_each_drv(dev->bus, NULL, &data,
>  					__device_attach_driver);
>  		if (!ret && allow_async && data.have_async) {
> @@ -557,6 +574,9 @@ static int __device_attach(struct device *dev, bool allow_async)
>  		} else {
>  			pm_request_idle(dev);
>  		}
> +
> +		if (dev->parent)
> +			pm_runtime_put(dev->parent);
>  	}
>  out_unlock:
>  	device_unlock(dev);

-- 
Lee Jones
Linaro STMicroelectronics Landing Team Lead
Linaro.org │ Open source software for ARM SoCs
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