From: Marek Vasut <marex@xxxxxxx> commit 1c45ba93d34cd6af75228f34d0675200c81738b5 upstream. KSZ8794CNX datasheet section 8.0 RESET CIRCUIT describes recommended circuit for interfacing with CPU/FPGA reset consisting of 10k pullup resistor and 10uF capacitor to ground. This circuit takes ~100 ms to rise enough to release the reset. For maximum supply voltage VDDIO=3.3V VIH=2.0V R=10kR C=10uF that is VDDIO - VIH t = R * C * -ln( ------------- ) = 10000*0.00001*-(-0.93)=0.093 s VDDIO so we need ~95 ms for the reset to really de-assert, and then the original 100us for the switch itself to come out of reset. Simply msleep() for 100 ms which fits the constraint with a bit of extra space. Fixes: 5b797980908a ("net: dsa: microchip: Implement recommended reset timing") Reviewed-by: Florian Fainelli <f.fainelli@xxxxxxxxx> Signed-off-by: Marek Vasut <marex@xxxxxxx> Cc: Michael Grzeschik <m.grzeschik@xxxxxxxxxxxxxx> Reviewed-by: Paul Barker <pbarker@xxxxxxxxxxxx> Reviewed-by: Andrew Lunn <andrew@xxxxxxx> Link: https://lore.kernel.org/r/20210120030502.617185-1-marex@xxxxxxx Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- drivers/net/dsa/microchip/ksz_common.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/net/dsa/microchip/ksz_common.c b/drivers/net/dsa/microchip/ksz_common.c index 489963664443..389abfd27770 100644 --- a/drivers/net/dsa/microchip/ksz_common.c +++ b/drivers/net/dsa/microchip/ksz_common.c @@ -400,7 +400,7 @@ int ksz_switch_register(struct ksz_device *dev, gpiod_set_value_cansleep(dev->reset_gpio, 1); usleep_range(10000, 12000); gpiod_set_value_cansleep(dev->reset_gpio, 0); - usleep_range(100, 1000); + msleep(100); } mutex_init(&dev->dev_mutex); -- 2.30.0