| Message ID | 20190609180621.7607-6-martin.blumenstingl@googlemail.com (mailing list archive) |
|---|---|
| State | Not Applicable |
| Headers | show |
| Series | stmmac: honor the GPIO flags for the PHY reset GPIO | expand |
On Sun, Jun 9, 2019 at 8:06 PM Martin Blumenstingl <martin.blumenstingl@googlemail.com> wrote: > The PHY reset line and interrupt line are swapped on the X96 Max > compared to the Odroid-N2 schematics. This means: > - GPIOZ_14 is the interrupt line (on the Odroid-N2 it's the reset line) > - GPIOZ_15 is the reset line (on the Odroid-N2 it's the interrupt line) > > Also 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_SOURCE because > otherwise the PHY will be stuck in "reset" state (because driving the > pin HIGH seeems to result in the same signal as driving it LOW). This far it seems all right. > Switch to GPIOZ_15 for the reset GPIO with the correct flags and drop > the "snps,reset-active-low" property as this is now encoded in the > GPIO_OPEN_SOURCE flag. Open source doesn't imply active low. We have this in stmmac_mdio_reset(): gpio_direction_output(data->reset_gpio, data->active_low ? 1 : 0); if (data->delays[0]) msleep(DIV_ROUND_UP(data->delays[0], 1000)); gpio_set_value(data->reset_gpio, data->active_low ? 0 : 1); if (data->delays[1]) msleep(DIV_ROUND_UP(data->delays[1], 1000)); gpio_set_value(data->reset_gpio, data->active_low ? 1 : 0); if (data->delays[2]) msleep(DIV_ROUND_UP(data->delays[2], 1000)); 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. 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. 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. After power on you need to actively de-assert the reset (to low) for it to go out of reset. > Fixes: 51d116557b2044 ("arm64: dts: meson-g12a-x96-max: Add Gigabit Ethernet Support") > Signed-off-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com> Other than the commit message: Reviewed-by: Linus Walleij <linus.walleij@linaro.org> Yours, Linus Walleij
Hi Linus, On Sun, Jun 9, 2019 at 11:17 PM Linus Walleij <linus.walleij@linaro.org> wrote: > > On Sun, Jun 9, 2019 at 8:06 PM Martin Blumenstingl > <martin.blumenstingl@googlemail.com> wrote: > > > The PHY reset line and interrupt line are swapped on the X96 Max > > compared to the Odroid-N2 schematics. This means: > > - GPIOZ_14 is the interrupt line (on the Odroid-N2 it's the reset line) > > - GPIOZ_15 is the reset line (on the Odroid-N2 it's the interrupt line) > > > > Also 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_SOURCE because > > otherwise the PHY will be stuck in "reset" state (because driving the > > pin HIGH seeems to result in the same signal as driving it LOW). > > This far it seems all right. ...except the "seeems" typo which I just noticed. thank you for sanity-checking this so far! > > Switch to GPIOZ_15 for the reset GPIO with the correct flags and drop > > the "snps,reset-active-low" property as this is now encoded in the > > GPIO_OPEN_SOURCE flag. > > Open source doesn't imply active low. > > We have this in stmmac_mdio_reset(): > > gpio_direction_output(data->reset_gpio, > data->active_low ? 1 : 0); > if (data->delays[0]) > msleep(DIV_ROUND_UP(data->delays[0], 1000)); > > gpio_set_value(data->reset_gpio, data->active_low ? 0 : 1); > if (data->delays[1]) > msleep(DIV_ROUND_UP(data->delays[1], 1000)); > > gpio_set_value(data->reset_gpio, data->active_low ? 1 : 0); > if (data->delays[2]) > msleep(DIV_ROUND_UP(data->delays[2], 1000)); > > 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. > 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 > 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 > Other than the commit message: > Reviewed-by: Linus Walleij <linus.walleij@linaro.org> thank you for looking into this! Martin [0] https://dn.odroid.com/S922X/ODROID-N2/Schematic/odroid-n2_rev0.4_20190307.pdf
On Sun, Jun 9, 2019 at 11:36 PM Martin Blumenstingl <martin.blumenstingl@googlemail.com> 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. > > 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)>; ? 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. Yours, Linus Walleij
Hi Linus, On Mon, Jun 10, 2019 at 12:06 AM Linus Walleij <linus.walleij@linaro.org> wrote: > > On Sun, Jun 9, 2019 at 11:36 PM Martin Blumenstingl > <martin.blumenstingl@googlemail.com> 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
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..c93b639679c0 100644 --- a/arch/arm64/boot/dts/amlogic/meson-g12a-x96-max.dts +++ b/arch/arm64/boot/dts/amlogic/meson-g12a-x96-max.dts @@ -186,9 +186,8 @@ phy-mode = "rgmii"; phy-handle = <&external_phy>; 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; }; &pwm_ef {
The PHY reset line and interrupt line are swapped on the X96 Max compared to the Odroid-N2 schematics. This means: - GPIOZ_14 is the interrupt line (on the Odroid-N2 it's the reset line) - GPIOZ_15 is the reset line (on the Odroid-N2 it's the interrupt line) Also 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_SOURCE because otherwise the PHY will be stuck in "reset" state (because driving the pin HIGH seeems to result in the same signal as driving it LOW). Switch to GPIOZ_15 for the reset GPIO with the correct flags and drop the "snps,reset-active-low" property as this is now encoded in the GPIO_OPEN_SOURCE flag. Fixes: 51d116557b2044 ("arm64: dts: meson-g12a-x96-max: Add Gigabit Ethernet Support") Signed-off-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com> --- arch/arm64/boot/dts/amlogic/meson-g12a-x96-max.dts | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-)