Messages in this thread | | | Date | Thu, 7 Dec 2023 06:15:02 +0100 | From | Oleksij Rempel <> | Subject | Re: [PATCH net-next v1 3/3] net: dsa: microchip: Fix PHY loopback configuration for KSZ8794 and KSZ8873 |
| |
On Thu, Dec 07, 2023 at 02:28:23AM +0200, Vladimir Oltean wrote: > On Tue, Nov 21, 2023 at 04:24:26PM +0100, Oleksij Rempel wrote: > > Correct the PHY loopback bit handling in the ksz8_w_phy_bmcr and > > ksz8_r_phy_bmcr functions for KSZ8794 and KSZ8873 variants in the ksz8795 > > driver. Previously, the code erroneously used Bit 7 of port register 0xD > > for both chip variants, which is actually for LED configuration. This > > update ensures the correct registers and bits are used for the PHY > > loopback feature: > > > > - For KSZ8794: Use 0xF / Bit 7. > > - For KSZ8873: Use 0xD / Bit 0. > > > > Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de> > > --- > > How did you find, and how did you test this, and on which one of the switches?
I tested it by using "ethtool -t lanX" command on KSZ8873. Before this patch the link will stop to work _after_ end of the selftest. The selftest will fail too.
After this patch, the selftest is passed, except of the TCP test. And link is working _after_ the selftest,
> Opening the KSZ8873 datasheet, I am confused about their description of > the "far-end loopback". They make it sound as if this loops the packets > _received_ from the media side of PHY port A back to the transmit side > of PHY port A. But the route that these packets take is through the MAC > of PHY port A, then the switching fabric, then PHY port B which reflects > them back to PHY port A, where they finally egress. > > Actually, they even go as far as saying that if you set the loopback bit > of port 1, the packets that will be looped back will be from port 2's > RXP/RXM to TXP/TXM pins, and viceversa. > > If true, I believe this isn't the behavior expected by phy_loopback(), > where the TX signals from the media side of the PHY are looped back into > the RX side. > >
-- Pengutronix e.K. | | Steuerwalder Str. 21 | http://www.pengutronix.de/ | 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 |
| |