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: 5b79798090 ("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>
1c45ba93d3