From: Marek Vasut marex@denx.de
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@gmail.com Signed-off-by: Marek Vasut marex@denx.de Cc: Michael Grzeschik m.grzeschik@pengutronix.de Reviewed-by: Paul Barker pbarker@konsulko.com Reviewed-by: Andrew Lunn andrew@lunn.ch Link: https://lore.kernel.org/r/20210120030502.617185-1-marex@denx.de Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- 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);