On Tue, Mar 1, 2022 at 10:59 AM Sean Anderson <sean.ander...@seco.com> wrote: > > Hi Tim, > > On 3/1/22 1:45 PM, Tim Harvey wrote: > > Greetings, > > > > I'm seeing an issue in U-Boot caused by gpio_request_by_name driving a > > GPIO output before it has been given an output level with > > {dm_}gpio_set_value. > > > > In my particular instance I have a network PHY that can encounter > > errata if it gets reset more than once (fun time with this one!) > > declared liks this: > > > > ðphy0 { > > reset-gpios = <&gpio3 0 GPIO_ACTIVE_LOW>; > > reset-assert-us = <1000>; > > reset-deassert-us = <300000>; > > }; > > > > Through testing it has been found that this PHY must be held in reset > > on power-up and released from reset only once. This is probably the > > third time I've run into such an issue in the 20 years I've worked > > with hardware - it's rare and certainly a result of poor reset > > handling in IC's but not a unique situation (especially at a time > > where we can't be too choosy about what parts go on boards). > > > > When eth-phy-uclass.c calls gpio_request_by_name(dev, "reset-gpios", > > 0, &uc_priv->reset_gpio, GPIOD_IS_OUT) direction_output is called > > which sets the GPIO to a high effectively taking the PHY out of reset > > before eth_phy_reset is called to do so. Setting the gpio as > > GPIO_ACTIVE_LOW will drive it low keeping it in reset until ready to > > de-assert it but then the polarity is inverted which results in the > > PHY being left in reset permanently. > > Can you try > > gpio_request_by_name(dev, "reset-gpios", 0, &uc_priv->reset_gpio, \ > GPIOD_IS_OUT | GPIOD_IS_OUT_ACTIVE) >
Sean, Thanks - this does work! When looking into this flag originally I misunderstood what that flag does. It causes the GPIO to be initialized in the 'active' (asserted) state vs the 'inactive' (de-asserted) state. I would certainly think that reset gpios should be initialized in the de-asserted case but I wonder if I go and change phy-reset-gpio in drivers/net/fec_mxc.c and phy-reset in dirvers/net/eth-phy-uclass.c if this would cause issues for other boards? diff --git a/drivers/net/eth-phy-uclass.c b/drivers/net/eth-phy-uclass.c index 1f285f7afd20..27b77444a0c5 100644 --- a/drivers/net/eth-phy-uclass.c +++ b/drivers/net/eth-phy-uclass.c @@ -137,7 +137,7 @@ static int eth_phy_of_to_plat(struct udevice *dev) /* search "reset-gpios" in phy node */ ret = gpio_request_by_name(dev, "reset-gpios", 0, &uc_priv->reset_gpio, - GPIOD_IS_OUT); + GPIOD_IS_OUT | GPIOD_IS_OUT_ACTIVE); if (ret && ret != -ENOENT) return ret; diff --git a/drivers/net/fec_mxc.c b/drivers/net/fec_mxc.c index 985b03844739..c1f4930172cf 100644 --- a/drivers/net/fec_mxc.c +++ b/drivers/net/fec_mxc.c @@ -1579,7 +1579,7 @@ static int fecmxc_of_to_plat(struct udevice *dev) #if CONFIG_IS_ENABLED(DM_GPIO) ret = gpio_request_by_name(dev, "phy-reset-gpios", 0, - &priv->phy_reset_gpio, GPIOD_IS_OUT); + &priv->phy_reset_gpio, GPIOD_IS_OUT | GPIOD_IS_OUT_ACTIVE); if (ret < 0) return 0; /* property is optional, don't return error! */ Tim > ? > > --Sean > > > This affects a wide variety of gpio based things including gpio-hogs. > > > > I'm looking for some input on how to best address this issue. I > > haven't finished walking through all the kernel code but I believe > > when a gpio is requested it does so without configuring that gpio. Any > > ideas? > > > > Best regards, > > > > Tim > >