On Thu, Nov 24, 2016 at 4:56 PM, Jerome Brunet <jbrunet@xxxxxxxxxxxx> wrote: > On Thu, 2016-11-24 at 15:34 +0100, Martin Blumenstingl wrote: >> Currently the dwmac-meson8b stmmac glue driver uses a hardcoded 1/4 >> cycle TX clock delay. This seems to work fine for many boards (for >> example Odroid-C2 or Amlogic's reference boards) but there are some >> others where TX traffic is simply broken. >> There are probably multiple reasons why it's working on some boards >> while it's broken on others: >> - some of Amlogic's reference boards are using a Micrel PHY >> - hardware circuit design >> - maybe more... >> >> This raises a question though: >> Which device is supposed to enable the TX delay when both MAC and PHY >> support it? And should we implement it for each PHY / MAC separately >> or should we think about a more generic solution (currently it's not >> possible to disable the TX delay generated by the RTL8211F PHY via >> devicetree when using phy-mode "rgmii")? > > Actually you can skip the part which activate the Tx-delay on the phy > by setting "phy-mode = "rgmii-id" instead of "rgmii" > > phy->interface will no longer be PHY_INTERFACE_MODE_RGMII > but PHY_INTERFACE_MODE_RGMII_ID. unfortunately this is not true for RTL8211F (I did my previous tests with the same expectation in mind)! the code seems to suggest that TX-delay is disabled whenever mode != PHY_INTERFACE_MODE_RGMII. BUT: on my device RTL8211F_TX_DELAY is set even before "phy_write(phydev, 0x11, reg);"! Based on what I found it seems that rgmii-id, rgmii-txid and rgmii-rxid are supposed to be handled by the PHY. That would mean that we have two problems here: 1) drivers/net/phy/realtek.c:rtl8211f_config_init should check for PHY_INTERFACE_MODE_RGMII_ID or PHY_INTERFACE_MODE_RGMII_TXID and enable the TX-delay in that case - otherwise explicitly disable it 2) dwmac-meson8b.c should only use the configured TX-delay for PHY_INTERFACE_MODE_RGMII @Florian: could you please share your thoughts on this (who handles the TX delay in which case)? Regards, Martin -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
