ARM: dts: Fix failing ethernet PHY detection on the LeMaker Banana Pi

While testing the daily builds of the Debian-Installer (d-i) on the LeMaker Banana Pi (a small, Allwinner A20-based board), I found that within the installer environment, the detection of the external Realtek ethernet PHY connected to the Allwinner A20 GMAC fails upon first loading of the stmmac driver:

[   77.235117] stmmaceth 1c50000.ethernet: no reset control found
[   77.235192]  Ring mode enabled
[   77.235202]  No HW DMA feature register supported
[   77.235211]  Normal descriptors
[   77.235219]  TX Checksum insertion supported
[   77.242678] libphy: stmmac: probed
[   77.242708] eth0: No PHY found

Just unloading the stmmac module and immediately afterwards modprobing it again results in proper detection of the PHY:

[  148.823456] stmmaceth 1c50000.ethernet: no reset control found
[  148.823487]  Ring mode enabled
[  148.823496]  No HW DMA feature register supported
[  148.823502]  Normal descriptors
[  148.823509]  TX Checksum insertion supported
[  148.854654] libphy: stmmac: probed
[  148.854683] eth0: PHY ID 001cc915 at 0 IRQ POLL (stmmac-0:00) active
[  148.854694] eth0: PHY ID 001cc915 at 1 IRQ POLL (stmmac-0:01)

On the Banana Pi, the PHY power supply is handled by a GPIO-controlled regulator:

gmac: ethernet at 01c50000 {
        pinctrl-names = "default";
        pinctrl-0 = <&gmac_pins_rgmii_a>;
        phy = <&phy1>;
        phy-mode = "rgmii";
        phy-supply = <&reg_gmac_3v3>;
        status = "okay";

        phy1: ethernet-phy at 1 {
                reg = <1>;
        };
};

reg_gmac_3v3: gmac-3v3 {
        compatible = "regulator-fixed";
        pinctrl-names = "default";
        pinctrl-0 = <&gmac_power_pin_bananapi>;
        regulator-name = "gmac-3v3";
        regulator-min-microvolt = <3300000>;
        regulator-max-microvolt = <3300000>;
        startup-delay-us = <50000>;
        enable-active-high;
        gpio = <&pio 7 23 0>;
};

and this problem did not show up on the hardware-wise rather similar Cubietech Cubietruck (same SoC, same external PHY, but no GPIO-controlled regulator for the PHY). Further tests have shown that increasing the startup-delay for the regulator solves the problem. The current sun7i-a20-bananapi.dts file (in linux-next, intended to go into kernel 3.19) sets startup-delay-us for the PHY's regulator to 50000. On my Banana Pi board, even with a value of 55000, the PHY detection does usually not work on the first probing inside d-i. Increasing the value to 57500 results in a successful probing most of the time, but not always; only setting it to 60000 results in a reliable PHY detection for me.

Following is a patch to increase the startup delay in the Banana Pi dts.

Regards,
Karsten

Karsten Merker (1):
ARM: dts: sunxi: Banana Pi: increase startup-delay for the GMAC PHY
regulator

 arch/arm/boot/dts/sun7i-a20-bananapi.dts |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Changes since V1:
- increased the delay from 60000us to 100000us to have a certain safety margin and cater for manufacturing variations as proposed by Hans de Goede.

1.7.10.4