[PATCH V2 0/1] ARM: dts: Fix failing ethernet PHY detection on the LeMaker Banana Pi

Karsten Merker
2014-11-11T23:01:45Z

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