From: Sebastian Hesselbarth <[email protected]> Date: Wed, 20 Nov 2013 21:21:46 +0100
> Ethernet PHYs consume a significant amount of power when link is detected. > Especially, for embedded systems it can be easily 20-40% of total system > power. Now, currently most likely all ethernet drivers leave PHYs powered > on, even if the device is taken down. Also, some stupid boot loaders power > on all PHYs available. > > This RFC deals with saving power consumed by ethernet PHYs, that have no > corresponding ethernet device driver or are attached to ethernet devices > which are taken down by user request, i.e. ifconfig ethN down. Ports with > no link, i.e. cable removed, are already quite good at power saving due to > PHY internal link detection. The idea is sound and the goal is of course valuable, but it brings up a chronically reoccurring issue as of late. You cannot reset the PHY or take it down without somehow retaining the settings the PHY had when you bring it back up. If I ifdown/ifup a device, my ethtool link configuration better be retained. This means the PHY layer must have a way to reprogram the device when it is brought back up, with whatever settings the software state things are there. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
