On Mon, 27 Jul 2015, Andy Shevchenko wrote:
> From: "Rafael J. Wysocki" <rafael.j.wysocki@xxxxxxxxx>
>
> 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@xxxxxxxxxxxxxxx>
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
> ---
> 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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