On Wed, Aug 28, 2013 at 11:38:58AM +0200, Wolfram Sang wrote: > On Tue, Aug 20, 2013 at 05:03:35PM +0300, Mika Westerberg wrote: > > From: Aaron Lu <aaron.lu@xxxxxxxxx> > > > > This patch adds runtime PM support for the I2C bus in a similar way that > > has been done for PCI bus already. This means that the I2C bus core > > prepares runtime PM for a client device just before a driver is about to be > > bound to it. Devices that are not bound to any driver are not prepared for > > runtime PM. > > > > In order to take advantage of this runtime PM support, the client device > > driver needs drop the device runtime PM reference count by calling > > pm_runtime_put() in its ->probe() callback and possibly implement rest of > > the runtime PM callbacks. > > > > However, this does not yet make runtime PM happen for the device, it has to > > be explicitly allowed from userspace per each I2C client device. The > > reason for this is that things like HID over I2C might not work as smoothly > > when runtime PM is active. So we leave it to the user to balance between > > performance and power efficiency. > > > > User can allow runtime PM for the client device by running: > > > > # echo auto > /sys/bus/i2c/devices/<device>/power/control > > > > and it can be forbidden again by: > > > > # echo on > /sys/bus/i2c/devices/<device>/power/control > > > > Status of the device can be monitored by reading files under the device > > power directory. > > > > If the driver doesn't support runtime PM (like most of the existing I2C > > client drivers), the device in question is regarded as being runtime PM > > active and powered on. > > > > The patch adds also runtime PM support for the adapter device because it is > > needed to be able to runtime power manage the I2C controller device. The > > adapter device is handled along with the I2C controller device (it uses > > pm_runtime_no_callbacks()). > > > > Signed-off-by: Aaron Lu <aaron.lu@xxxxxxxxx> > > Signed-off-by: Mika Westerberg <mika.westerberg@xxxxxxxxxxxxxxx> > > CCing ALKML. Would appreciate comments/tags from the runtime-PM users of > the ARM world. Any comments on this? I can resend the whole series with ALKML included if that helps. -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
