Hi Linus, On Mon, Jun 10, 2019 at 12:06 AM Linus Walleij <linus.walleij@xxxxxxxxxx> wrote: > > On Sun, Jun 9, 2019 at 11:36 PM Martin Blumenstingl > <martin.blumenstingl@xxxxxxxxxxxxxx> wrote: > > > > If "snps,reset-active-low" was set it results in the sequence 1, 0, 1 > > > if it is not set it results in the sequence 0, 1, 0. > > > > I'm changing this logic with earlier patches of this series. > > can you please look at these as well because GPIO_OPEN_SOURCE doesn't > > work with the old version of stmmac_mdio_reset() that you are showing. > > OK but the logic is the same, just that the polarity handling is moved > into gpiolib. > > > > The high (reset) is asserted by switching the pin into high-z open drain > > > mode, which happens by switching the line into input mode in some > > > cases. > > > > > > I think the real reason it works now is that reset is actually active high. > > > > let me write down what I definitely know so far > > > > the RTL8211F PHY wants the reset line to be LOW for a few milliseconds > > to put it into reset mode. > > driving the reset line HIGH again takes it out of reset. > > > > Odroid-N2's schematics [0] (page 30) shows that there's a pull-up for > > the PHYRSTB pin, which is also connected to the NRST signal which is > > GPIOZ_15 > > Looks correct, R143 is indeed a pull up indicating that the line is > open drain, active low. good so far > > > It makes a lot of sense, since if it resets the device when set as input > > > (open drain) it holds all devices on that line in reset, which is likely > > > what you want as most GPIOs come up as inputs (open drain). > > > A pull-up resistor will ascertain that the devices are in reset. > > > > my understanding is that the pull-up resistor holds it out of reset > > driving GPIOZ_15's (open drain) output LOW pulls the signal to ground > > and asserts the reset > > Yep that seems correct. > > Oh I guess it is this: > > amlogic,tx-delay-ns = <2>; > - snps,reset-gpio = <&gpio GPIOZ_14 0>; > + snps,reset-gpio = <&gpio GPIOZ_15 GPIO_OPEN_SOURCE>; > snps,reset-delays-us = <0 10000 1000000>; > - snps,reset-active-low; > > Can you try: > snps,reset-gpio = <&gpio GPIOZ_15 (GPIO_ACTIVE_LOW | GPIO_OPEN_DRAIN)>; > ? I tried it and it works! > Open source is nominally (and rarely) used for lines that are active high. > For lines that are active low, we want to use open drain combined > with active low. thank you for the explanation - I'll take your version for v2 :) Martin
