On Wednesday, April 18, 2012, huang ying wrote: > On Wed, Apr 18, 2012 at 4:20 AM, Rafael J. Wysocki <rjw@xxxxxxx> wrote: > > On Tuesday, April 17, 2012, huang ying wrote: > >> On Tue, Apr 17, 2012 at 1:07 AM, Rafael J. Wysocki <rjw@xxxxxxx> wrote: > >> > Moreover, I really don't think it's a good idea to put PCI Express ports into > >> > low-power states in general. It might work on your platform, whatever it is, > >> > but that doesn't mean it's going to work on every PCI Express system out > >> > there. I actually know of a number of such systems where it surely won't > >> > work at all. > >> > >> The runtime PM support for PCIe port is not turned on by default, we need > >> > >> # echo auto > /sys/devices/pcixxxx:xx/<pci id>/power/control > >> > >> to turn on it. And we will turn on it on system it works. Is this sufficient? > > > > No, it is not. In some cases it shouldn't be enabled at all for PCI Express > > ports, as far as I can say, so to be on the safe side we should only enable it > > on platforms where PCI Express ports are known to work correctly with runtime PM. > > Sorry, I did not catch your idea exactly. I think disable it by > default and enable it by sysfs interface is what you suggested, isn't > it? No, it isn't. User space shouldn't be able to enable functionality that's going to break on a subset of systems. > Or you suggest something like "white list"? Yes, something like this. Thanks, Rafael -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
