Stm32mp157 Ethernet problem

[Yli.8]

An urgent problem occurred in stm32mp157. I used ksz9031 network chip, but it could not be used. The LOG is as follows,

[  18.996823] Micrel KSZ9031 Gigabit PHY stmmac-0:00: attached PHY driver [Micrel KSZ9031 Gigabit PHY] (mii_bus:phy_addr=stmmac-0:00, irq=POLL)

     Starting Wait for Network to be Configured...

[  19.122107] stm32-dwmac 5800a000.ethernet: Failed to reset the dma

[  19.127072] stm32-dwmac 5800a000.ethernet eth0: stmmac_hw_setup: DMA engine initialization failed

[  19.135979] stm32-dwmac 5800a000.ethernet eth0: stmmac_open: Hw setup failed

I can't solve this problem

[PatrickF]

See https://wiki.st.com/stm32mpu/wiki/Ethernet_overview#How_to_debug

This error is usually linked to a clock not active on the ETH IP boundary when the reset is requested (see RM0436, look at RCC section "Clock distribution for Ethernet (ETH)"). E.g. check if clocks are present on ETH_CLK125 and ETH_RX_CLK pins.

Is your PHY set-up in similar way that the one on EV1 (MB1262) or DK2 (MB1272) boards ? You could also see AN5031.

Check also if you PHY is powered at the time of the ETH reset.

[Yli.8]

• This is my ksz9031 circuit diagram

[PatrickF]

CLK125_NDO (125MHz clock from PHY) should normally be connected to ETH_CLK125 pin (PG5).

if you omit that intentionally, you need to feed internally the ETH with a precise 125MHz clock from RCC pll3_q or pll4_p (this might constrain your clock tree choices) and do the relevant settings in the DeviceTree (see https://wiki.st.com/stm32mpu/wiki/Ethernet_device_tree_configuration)

[Yli.8]

• Can you simply provide Settings for these two clocks on the device tree

[Yli.8]

• Can you provide more description of configuring device tree clock

[AntonioST · Accepted solution]

Hi,

the pin 41 of KSZ9031 should provide the 125 MHz clock to STM32MP1 (and this is the simpler and preferred solution), but in your schematic it is instead connected only to a test point.

If you cannot rework your board, you need to provide the 125 MHz internally in STM32MP1.

Check the STM32MP1 Reference Manual at chapter 10.4.8 "clock distribution for Ethernet (ETH)".

The input named "ETH_CLK125" is the one missing in your board, so has to be replaced with a 125 MHz clock arriving from pll4_p_ck or pll3_q_ck. Now we need to set all the internal switches to achieve this.

Use also the document Documentation/devicetree/bindings/net/stm32-dwmac.txt for reference.

1) mux between ETH_CLK125 and eth_clk_fb: change its position adding DT property:

st,eth_clk_sel = <1>;

2) enable the gate controlled by ETHCKEN: for this you need to add two more clocks in the DT:

   To clock-names add "eth-ck" and "syscfg-clk"

   To clocks add ETHCK_K and SYSCFG

The point 1) and 2) can be put in your board DT as:

&ethernet0 {
    status = "okay";
    st,eth_clk_sel = <1>;
    clock-names = "stmmaceth",
        "mac-clk-tx",
        "mac-clk-rx",
        "eth-ck",
        "syscfg-clk",
        "ethstp";
    clocks = <&rcc ETHMAC>,
        <&rcc ETHTX>,
        <&rcc ETHRX>,
        <&rcc ETHCK_K>,
        <&rcc SYSCFG>,
        <&rcc ETHSTP>;
};

Now it remains the mux between pll4_p_ck or pll3_q_ck and the frequency from the PLL. This has to be done in the DT of tf-a (if you use secure boot) or DT of U-Boot (if you use the basic boot). The DT is the same in the two cases, just stored in a different file:

- tf-a has DT in folder ./fdts/

- u-boot has DT in folder ./arch/arm/dts/

At linux boot, this command gives you the dump of the clock tree. You need to verify there if the clock frequency is correct

cat /sys/kernel/debug/clk/clk_summary

You also need to set a frequency that is suitable for all the users of the same PLL

Let's go to edit the DT!

4) mux source: replace CLK_ETH_DISABLED with CLK_ETH_PLL4P or with CLK_ETH_PLL3Q

in my test I used pll4_p

5) change the numbers in node "pll3: st,pll@2" or "pll4: st,pll@3"

   one possible settings for pll4_p at 125 MHz (suppose crystal on HSE is 24 MHz) is

/* VCO = 750.0 MHz, P=125, Q=62.5, R=62.5 */
pll4: st,pll@3 {
    cfg = <3 124 5 11 11 PQR(1,1,1)>;
};

[EBaum.2]

For anyone trying to solve this problem today, please note there is a crucial typo in Antonio's answer.

This is incorrect:

st,eth_clk_sel = <1>;

Using that will cause your clocks to not enable. You must use the following declaration:

st,eth-clk-sel = <1>;

This was found after hours of testing and then reviewing the source code to determine how to enable the PPL4P clocks, which were stuck in a disabled mode.