[PATCH 1/3] net: dsa: ksz9477: always toggle reset gpio if available

[Ahmad Fatoum]

The barebox driver currently only ensures that the switch is out of
reset, but doesn't actually trigger a reset pulse.

The Linux driver, on the other hand, holds reset active for 10ms and
then waits a whopping 100ms after reset deassertion.

This seems excessive by a thousandfold for at least KSZ9893R[1], whose
datasheet states:

  After the de-assertion of reset, it is recommended to wait a minimum of
  100µs before starting to program the device through any interface.

Therefore, let's pulse the reset like Linux does and give the switch 100
microseconds before continuing with the driver probe.

[1]: DS00002420E-page 176

Signed-off-by: Ahmad Fatoum <a.fatoum at pengutronix.de>
---
 drivers/net/ksz9477.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ksz9477.c b/drivers/net/ksz9477.c
index 1abea9d04017..5c5f4ec8d995 100644
--- a/drivers/net/ksz9477.c
+++ b/drivers/net/ksz9477.c
@@ -433,8 +433,10 @@ static int microchip_switch_probe(struct device *dev)
 	if (IS_ERR(gpio)) {
 		dev_warn(dev, "Failed to get 'reset' GPIO (ignored)\n");
 	} else if (gpio) {
-		mdelay(1);
+		gpiod_set_value(gpio, true);
+		mdelay(10);
 		gpiod_set_value(gpio, false);
+		udelay(100);
 	}
 
 	ksz_reset_switch(dev->priv);
-- 
2.39.2