|
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 either in runtime_suspend()
callbacks. Why
should we not use those functions in a driver suspend callback implementation ? Thx Loic Intel Corporation SAS (French simplified joint stock company) Registered headquarters: "Les Montalets"- 2, rue de Paris, 92196 Meudon Cedex, France Registration Number: 302 456 199 R.C.S. NANTERRE Capital: 4,572,000 Euros This e-mail and any attachments may contain confidential material for the sole use of the intended recipient(s). Any review or distribution by others is strictly prohibited. If you are not the intended recipient, please contact the sender and delete all copies. |
_______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
