net: mdio: mdio-bcm-unimac: Delay before first poll

With a clock interval of 400 nsec and a 64 bit transactions (32 bit
preamble & 16 bit control & 16 bit data), it is reasonable to assume
the mdio transaction will take 25.6 usec. Add a 30 usec delay before
the first poll to reduce the chance of a 1000-2000 usec sleep.

Reduce the timeout from 1000ms to 100ms as it is unlikely for the bus
to take this long.
Signed-off-by: Justin Chen <justin.chen@broadcom.com>
Acked-by: Florian Fainelli <florian.fainelli@broadcom.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Link: https://lore.kernel.org/r/20231213222744.2891184-2-justin.chen@broadcom.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/mdio/mdio-bcm-unimac.c

@@ -81,7 +81,13 @@ static inline unsigned int unimac_mdio_busy(struct unimac_mdio_priv *priv)
 static int unimac_mdio_poll(void *wait_func_data)
 {
 	struct unimac_mdio_priv *priv = wait_func_data;
-	unsigned int timeout = 1000;
+	unsigned int timeout = 100;
+
+	/*
+	 * C22 transactions should take ~25 usec, will need to adjust
+	 * if C45 support is added.
+	 */
+	udelay(30);
 
 	do {
 		if (!unimac_mdio_busy(priv))