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
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