[PATCH net-next] net: dsa: microchip: Adjust reset release timing to match reference reset circuit
From: Marek Vasut <marex@denx.de>
Date: 2021-01-20 02:02:45
Subsystem:
microchip ksz series ethernet switch driver, networking drivers, networking [dsa], the rest · Maintainers:
Woojung Huh, Andrew Lunn, "David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Andrew Lunn, Vladimir Oltean, Linus Torvalds
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")
Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Andrew Lunn <andrew@lunn.ch>
Cc: Florian Fainelli <f.fainelli@gmail.com>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: Michael Grzeschik <redacted>
Cc: Paul Barker <redacted>
---
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);
--
2.29.2