On 12/06/2019 22:55, Martin Blumenstingl wrote:
> The Odroid-N2 schematics show that the following pins are used for the
> reset and interrupt lines:
> - GPIOZ_14 is the PHY interrupt line
> - GPIOZ_15 is the PHY reset line
>
> The GPIOZ_14 and GPIOZ_15 pins are special. The datasheet describes that
> they are "3.3V input tolerant open drain (OD) output pins". This means
> the GPIO controller can drive the output LOW to reset the PHY. To
> release the reset it can only switch the pin to input mode. The output
> cannot be driven HIGH for these pins.
> This requires configuring the reset line as GPIO_OPEN_DRAIN because
> otherwise the PHY will be stuck in "reset" state (because driving the
> pin HIGH seems to result in the same signal as driving it LOW).
>
> The reset line works together with a pull-up resistor (R143 in the
> Odroid-N2 schematics). The SoC can drive GPIOZ_14 LOW to assert the PHY
> reset. However, since the SoC can't drive the pin HIGH (to release the
> reset) we switch the mode to INPUT and let the pull-up resistor take
> care of driving the reset line HIGH.
>
> Switch to GPIOZ_15 for the PHY reset line instead of using GPIOZ_14
> (which actually is the interrupt line).
> Move from the "snps" specific resets to the MDIO framework's
> reset-gpios because only the latter honors the GPIO flags.
> Use the GPIO flags (GPIO_ACTIVE_LOW | GPIO_OPEN_DRAIN) to match with
> the pull-up resistor because this will:
> - drive the output LOW to reset the PHY (= active low)
> - switch the pin to INPUT mode so the pull-up will take the PHY out of
> reset
>
> Fixes: 51d116557b2044 ("arm64: dts: meson-g12a-x96-max: Add Gigabit Ethernet
> Support")
> Signed-off-by: Martin Blumenstingl <martin.blumensti...@googlemail.com>
> ---
> arch/arm64/boot/dts/amlogic/meson-g12a-x96-max.dts | 7 ++++---
> 1 file changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/arch/arm64/boot/dts/amlogic/meson-g12a-x96-max.dts
> b/arch/arm64/boot/dts/amlogic/meson-g12a-x96-max.dts
> index 98bc56e650a0..de58d7817836 100644
> --- a/arch/arm64/boot/dts/amlogic/meson-g12a-x96-max.dts
> +++ b/arch/arm64/boot/dts/amlogic/meson-g12a-x96-max.dts
> @@ -176,6 +176,10 @@
> reg = <0>;
> max-speed = <1000>;
> eee-broken-1000t;
> +
> + reset-assert-us = <10000>;
> + reset-deassert-us = <30000>;
> + reset-gpios = <&gpio GPIOZ_15 (GPIO_ACTIVE_LOW |
> GPIO_OPEN_DRAIN)>;
> };
> };
>
> @@ -186,9 +190,6 @@
> phy-mode = "rgmii";
> phy-handle = <&external_phy>;
> amlogic,tx-delay-ns = <2>;
> - snps,reset-gpio = <&gpio GPIOZ_14 0>;
> - snps,reset-delays-us = <0 10000 1000000>;
> - snps,reset-active-low;
> };
>
> &pwm_ef {
>
Thanks for spotting this:
Reviewed-by: Neil Armstrong <narmstr...@baylibre.com>
