Since commit e9f2cefb0cdc2ae ("usb: phy: generic: migrate to gpio_desc") a
kernel hang is observed on imx51-babbage board:
[ 1.392824] ci_hdrc ci_hdrc.1: doesn't support gadget
[ 1.397975] ci_hdrc ci_hdrc.1: EHCI Host Controller
[ 1.403205] ci_hdrc ci_hdrc.1: new USB bus registered, assigned bus number 1
[ 1.422335] ci_hdrc ci_hdrc.1: USB 2.0 started, EHCI 1.00
[ 1.432962] hub 1-0:1.0: USB hub found
[ 1.437119] hub 1-0:1.0: 1 port detected
This hang happens because the reset GPIO stays at logic level 0.
The USB PHY reset gpio is defined in the dts file as:
reset-gpios = <&gpio2 5 GPIO_ACTIVE_LOW>;
, which means it is active low, so what the gpio reset pin needs to do in this
case is the following:
- Go to logic level 0 to reset the USB PHY
- Stay at 0 for a bit
- Go back to logic level 1
When switching to gpiod API we need to following according to
Documentation/gpio/consumer.txt:
"The first thing a driver must do with a GPIO is setting its direction. If no
direction-setting flags have been given to gpiod_get*(), this is done by
invoking one of the gpiod_direction_*() functions:
int gpiod_direction_input(struct gpio_desc *desc)
int gpiod_direction_output(struct gpio_desc *desc, int value)"
Since no direction-setting flags have been given to devm_gpiod_get_optional()
in our case, we need to use gpiod_direction_output to comply with the gpiod API.
With this change the USB PHY reset performs a proper reset, the kernel boots
fine and USB host is functional.
Signed-off-by: Fabio Estevam <fabio.estevam@xxxxxxxxxxxxx>
---
Change since v1:
- Explain the need for using gpiod_direction_output()
drivers/usb/phy/phy-generic.c | 9 +++++----
1 file changed, 5 insertions(+), 4 deletions(-)
diff --git a/drivers/usb/phy/phy-generic.c b/drivers/usb/phy/phy-generic.c
index ef82711..433bf6d 100644
--- a/drivers/usb/phy/phy-generic.c
+++ b/drivers/usb/phy/phy-generic.c
@@ -63,11 +63,12 @@ static int nop_set_suspend(struct usb_phy *x, int suspend)
static void nop_reset_set(struct usb_phy_generic *nop, int asserted)
{
- if (nop->gpiod_reset)
- gpiod_set_value(nop->gpiod_reset, asserted);
+ if (!nop->gpiod_reset)
+ return;
- if (!asserted)
- usleep_range(10000, 20000);
+ gpiod_direction_output(nop->gpiod_reset, !asserted);
+ usleep_range(10000, 20000);
+ gpiod_set_value(nop->gpiod_reset, asserted);
}
/* interface to regulator framework */
--
1.9.1
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