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Title: ethernet flow control support [Print This Page]
Author: v.vacek    Time: 4/3/2019 14:13
Title: ethernet flow control support
Is there possibility to switch on flow control on ethernet interface? Now is the ethernet PHY layer chip RTL8211E set after hw reset to default without flow control announcement. There is no activated control driver in the Linux kernel to set it. Thanks. Vaclav.
Author: penguin    Time: 4/4/2019 17:22
In drivers/net/ethernet/stmicro/stmmac/stmmac_main.c , there is a flow control module parameter.

  1. static int flow_ctrl = FLOW_OFF;                                                                                                                  
  2. module_param(flow_ctrl, int, S_IRUGO | S_IWUSR);                                                                                                   
  3. MODULE_PARM_DESC(flow_ctrl, "Flow control ability [on/off]");                                                                                      
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It defaults to FLOW_OFF. You can modify it and recompile the kernel to check if it works.
Author: penguin    Time: 4/4/2019 17:28
Or follow the commands below to have a hot fix:

  1. cd /sys/bus/platform/drivers/rk_gmac-dwmac

  3. # unbind the ethernet device from the driver
  4. echo fe300000.ethernet > unbind

  6. # turn on flow_ctrl
  7. echo 1 > /sys/module/stmmac/parameters/flow_ctrl

  9. # bind the ethernet device back
  10. echo fe300000.ethernet > bind
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After these commands, there're messages from the kernel:

  2. [11547.465973] force_sf_dma_mode is ignored if force_thresh_dma_mode is set.[11547.466691] rk_gmac-dwmac fe300000.ethernet: Looking up phy-supply from device tree
  3. [11547.467826] rk_gmac-dwmac fe300000.ethernet: clock input or output? (input).
  4. [11547.468510] rk_gmac-dwmac fe300000.ethernet: TX delay(0x28).
  5. [11547.469033] rk_gmac-dwmac fe300000.ethernet: RX delay(0x1b).
  6. [11547.469635] rk_gmac-dwmac fe300000.ethernet: integrated PHY? (no).
  7. [11547.470722] rk_gmac-dwmac fe300000.ethernet: cannot get clock clk_mac_speed
  8. [11547.471349] rk_gmac-dwmac fe300000.ethernet: clock input from PHY
  9. [11547.476958] rk_gmac-dwmac fe300000.ethernet: init for RGMII
  10. [11547.486003] stmmac - user ID: 0x10, Synopsys ID: 0x35
  11. [11547.486561]  Ring mode enabled
  12. [11547.486844]  DMA HW capability register supported
  13. [11547.487250]  Normal descriptors
  14. [11547.487688]  RX Checksum Offload Engine supported (type 2)
  15. [11547.488177]  Wake-Up On Lan supported
  16. [11547.488617]  Enable RX Mitigation via HW Watchdog Timer
  17. [11547.491855] of_get_named_gpiod_flags: parsed 'snps,reset-gpio' property of node '/ethernet@fe300000[0]' - status (0)
  18. [11547.492826] gpio-111 (mdio-reset): gpiod_request: status -16
  19. [11547.509629] libphy: stmmac: probed
  20. [11547.509949] eth%d: PHY ID 001cc915 at 0 IRQ POLL (stmmac-0:00) active
  21. [11547.510616] eth%d: PHY ID 001cc915 at 1 IRQ POLL (stmmac-0:01)
  22. root@firefly:/sys/bus/platform/drivers/rk_gmac-dwmac# [11547.615421] IPv6: ADDRCONF(NETDEV_UP): eth0: link is not ready

  24. root@firefly:/sys/bus/platform/drivers/rk_gmac-dwmac# [11550.624270] rk_gmac-dwmac fe300000.ethernet eth0: Link is Up - 100Mbps/Full - flow control rx/tx
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The last line is indicating flow control enabled, right?  Plz check
Author: v.vacek    Time: 5/13/2019 20:10
penguin Posted at 4/4/2019 17:28
Or follow the commands below to have a hot fix:

It doesn't work. The stmmac driver uses kernel generic-phy driver for PHY layer chip /RTL8211E/ and this driver has flow control advertisement switched off.
                                                                                                Vaclav.
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