On Mon, 21 Mar 2011, Martin, LoicX wrote: > Hi > > I found in the linux kernel documentation : > In /power/pci.h > 2.4.1. System Suspend > > PCI device drivers (that don't implement legacy power management callbacks) are > generally not expected to prepare devices for signaling wakeup or to put them > into low-power states. However, if one of the driver's suspend callbacks > (pm->suspend() or pm->suspend_noirq()) saves the device's standard configuration > registers, pci_pm_suspend_noirq() will assume that the device has been prepared > to signal wakeup and put into a low-power state by the driver (the driver is > then assumed to have used the helper functions provided by the PCI subsystem for > this purpose). PCI device drivers are not encouraged to do that, but in some > rare cases doing that in the driver may be the optimum approach. > > 3.1.2 suspend() > > It is not required (in fact it even is > not recommended) that a PCI driver's suspend() callback save the standard > configuration registers of the device, prepare it for waking up the system, or > put it into a low-power state. All of these operations can very well be taken > care of by the PCI subsystem, without the driver's participation. > > 2.3. Runtime Device Power Management > > It is expected that the device driver's pm->runtime_suspend() callback will > not attempt to prepare the device for signaling wakeup or to put it into a > low-power state. The driver ought to leave these tasks to the PCI subsystem > that has all of the information necessary to perform them. > > > So I was wondering why in the kernel sources, most of the PCI drivers were using pci_set_power_state, as well pci_save_state either in suspend() callbacks Perhaps because those PCI drivers were written before the documentation, using legacy power management. > either in runtime_suspend() callbacks. There should not be any drivers doing that, because runtime_suspend is a relatively recent addition. Can you provide examples? > Why should we not use those functions in a driver suspend callback implementation ? Because it would duplicate code that is already present in the PCI core. Alan Stern _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
