Hi Andrew and Florian, On 28/11/16 15:14, Andrew Lunn wrote: > On Mon, Nov 28, 2016 at 02:24:30PM +0100, Allan W. Nielsen wrote: > > From: Raju Lakkaraju <raju.lakkar...@microsemi.com> > > > > 3 types of PHY loopback are supported. > > i.e. Near-End Loopback, Far-End Loopback and External Loopback. > Is this integrated with ethtool --test? You only want the PHY to go > into loopback mode when running ethtool --test external_lb or maybe > ethtool --test offline. There are other use-cases for enabling PHY loopback:
1) If the PHY is connected to a switch then a loop-port is sometime used to "force/enable" one or more extra pass through the switch core. This "hack" can sometime be used to achieve new functionality with existing silicon. 2) Existing user-space application may expect to be able to do the testing on its own (generate/validate the test traffic). > What i think should happen is that this tunable sets the mode the > PHY will go into when loopback is enabled. It does not however > enable loopback. That does not make a lot of sense with the "FAR" loopback (it is looping received traffic back into the wire). > It is running ethtool --test which actually enables > the loopback, probably by setting BMCR_LOOPBACK. Once the test is > finished, the bit is cleared and the PHY goes back into normal > operation. We are always happy to integrate with any existing functionality, but as I understand "ethtool --test" then intention is to perform a test and then bring back the PHY in to a "normal" state (I may be wrong...). The idea with this patch is to allow configuring loopback more "permanently" (userspace can decide when to activate and when to de-activate). I should properly have made that clear in the cover letter. Please let me know what you think. /Allan
