Hello folks, I've got a problem, which has been blowing by head up for more than three weeks now, and I'm desperately need your help in that matter. See our Baikal-T1 SoC is created with two DW GMAC v3.73a IP-cores. Each core has been synthesized with two GPIOs: one as GPI and another as GPO. There are multiple Baikal-T1-based devices have been created so far with active GMAC interface usage and each of them has been designed like this:
+------------------------+ | Baikal-T1 +------------+ +------------+ | SoC | DW GMAC | | Some PHY | | | Rx-clk+<------+Rx-clk | | | | | | | | GPI+<------+#IRQ | | | | | | | | RGMII+<----->+RGMII | | | MDIO+<----->+MDIO | | | | | | | | GPO+------>+#RST | | | | | | | | Tx-clk+------>+Tx-clk | | | | | | | +------------+ +------------+ +------------------------+ Each of such devices has got en external RGMII-PHY attached configured via the MDIO bus with Rx-clock supplied by the PHY and Tx-clock consumed by it. The main peculiarity of such configuration is that the DW GMAC GPIOs have been used to catch the PHY IRQs and to reset the PHY. Seeing the GPIOs support hasn't been added to the STMMAC driver it's the very first setup for now, which has been using them. Anyway the hardware setup depicted above doesn't seem problematic at the first glance, but in fact it is. See, the DW *MAC driver (STMMAC ethernet driver) is doing the MAC reset each time it performs the device open or resume by means of the call-chain: stmmac_open()---+ +->stmmac_hw_setup()->stmmac_init_dma_engine()->stmmac_reset(). stmmac_resume()-+ Such reset causes the whole interface reset: MAC, DMA and, what is more important, GPIOs as being exposed as part of the MAC registers. That in our case automatically causes the external PHY reset, what neither the STTMAC driver nor the PHY subsystem expect at all. Moreover the stmmac_reset() method polls the DMA_BUS_MODE.SFT_RESET flag state to be sure the MAC is successfully completed. But since the external PHY has got in reset state it doesn't generate the Rx-clk signal. Due to that the MAC-DMA won't get out of the reset state so the stmmac_reset() method will return timeout error. Of course I could manually restore the GPIOs state in the stmmac_reset() before start to poll the SFT_RESET flag, which may release the PHY reset. But that seems more like a workaround, because the PHY still has been in reset and need to be reinitialized anyway. Moreover some PHY may need to have more complicated reset cycle with certain delays between RST assertion/de-assertion, so the workaround won't work well for them. To sum it up my question is what is the right way to resolve the problem described above? My first idea was to just move the MAC reset from the net-device open()/close() callbacks to the stmmac_dvr_probe()/stmmac_dvr_remove() functions and don't reset the whole interface on each device open. The problems we may have in that case is due to the suspend/resume procedures, which for some reason require the MAC reset too. That's why I need your help in this matter. Do you have any idea how to gently add the GPIOs support and don't break the STMMAC driver? One more tiny question regarding the DW *MAC drivers available in kernel. Aside of the DW GMAC Baikal-T1 SoC has also got DW xGMAC v2.11a embedded with XPCS PHY attached. My question is what driver should we better use to handle our xGMAC interface? AFAICS there are three DW *MAC-related drivers the kernel currently provides: 1) drivers/net/ethernet/stmicro/stmmac 2) drivers/net/ethernet/amd/ 3) drivers/net/ethernet/synopsys/ xGBE interface is supported by the drivers 1) and 2). In accordance with https://www.spinics.net/lists/netdev/msg414148.html all xGMAC related parts should have been added to 2), but recently the XGMAC support has been added to 1). So I am confused what driver is now supposed to be used for new xGMACs? Regards, -Sergey