From: Geert Uytterhoeven geert+renesas@glider.be
commit 929d8490f8790164f5f63671c1c58d6c50411cb2 upstream.
Commit b9bf5612610aa7e3 ("ARM: dts: am335x-bone-common: Increase MDIO reset deassert time") already increased the MDIO reset deassert delay from 6.5 to 13 ms, but this may still cause Ethernet PHY probe failures:
SMSC LAN8710/LAN8720 4a101000.mdio:00: probe with driver SMSC LAN8710/LAN8720 failed with error -5
On BeagleBone Black Rev. C3, ETH_RESETn is controlled by an open-drain AND gate. It is pulled high by a 10K resistor, and has a 4.7µF capacitor to ground, giving an RC time constant of 47ms. As it takes 0.7RC to charge the capacitor above the threshold voltage of a CMOS input (VDD/2), the delay should be at least 33ms. Considering the typical tolerance of 20% on capacitors, 40ms would be safer. Add an additional safety margin and settle for 50ms.
Signed-off-by: Geert Uytterhoeven geert+renesas@glider.be Reviewed-by: Roger Quadros rogerq@kernel.org Link: https://lore.kernel.org/r/9002a58daa1b2983f39815b748ee9d2f8dcc4829.173036693... Signed-off-by: Kevin Hilman khilman@baylibre.com Signed-off-by: Nobuhiro Iwamatsu (CIP) nobuhiro1.iwamatsu@toshiba.co.jp --- arch/arm/boot/dts/ti/omap/am335x-bone-common.dtsi | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/arm/boot/dts/ti/omap/am335x-bone-common.dtsi b/arch/arm/boot/dts/ti/omap/am335x-bone-common.dtsi index 4867ff28c97e..27e73e745e25 100644 --- a/arch/arm/boot/dts/ti/omap/am335x-bone-common.dtsi +++ b/arch/arm/boot/dts/ti/omap/am335x-bone-common.dtsi @@ -385,7 +385,7 @@ /* Support GPIO reset on revision C3 boards */ reset-gpios = <&gpio1 8 GPIO_ACTIVE_LOW>; reset-assert-us = <300>; - reset-deassert-us = <13000>; + reset-deassert-us = <50000>; }; };