From mboxrd@z Thu Jan 1 00:00:00 1970 From: f.fainelli@gmail.com (Florian Fainelli) Date: Sat, 26 Nov 2016 21:53:47 -0800 Subject: [PATCH 1/2] Documentation: devicetree: clarify usage of the RGMII phy-modes In-Reply-To: <20161125131201.19994-2-martin.blumenstingl@googlemail.com> References: <20161125131201.19994-1-martin.blumenstingl@googlemail.com> <20161125131201.19994-2-martin.blumenstingl@googlemail.com> Message-ID: <61b8fa1b-e947-16ca-fb97-02a1125042aa@gmail.com> To: linus-amlogic@lists.infradead.org List-Id: linus-amlogic.lists.infradead.org On 11/25/2016 05:12 AM, Martin Blumenstingl wrote: > RGMII requires special RX and/or TX delays depending on the actual > hardware circuit/wiring. These delays can be added by the MAC, the PHY > or the designer of the circuit (the latter means that no delay has to > be added by PHY or MAC). > There are 4 RGMII phy-modes used describe where a delay should be > applied: > - rgmii: the RX and TX delays are either added by the MAC (where the > exact delay is typically configurable, and can be turned off when no > extra delay is needed) or not needed at all (because the hardware > wiring adds the delay already). The PHY should neither add the RX nor > TX delay in this case. > - rgmii-rxid: configures the PHY to enable the RX delay. The MAC should > not add the RX delay in this case. > - rgmii-txid: configures the PHY to enable the TX delay. The MAC should > not add the TX delay in this case. > - rgmii-id: combines rgmii-rxid and rgmii-txid and thus configures the > PHY to enable the RX and TX delays. The MAC should neither add the RX > nor TX delay in this case. > > Document these cases in the ethernet.txt documentation to make it clear > when to use each mode. > If applied incorrectly one might end up with MAC and PHY both enabling > for example the TX delay, which breaks ethernet TX traffic on 1000Mbit/s > links. > > Signed-off-by: Martin Blumenstingl Reviewed-by: Florian Fainelli -- Florian