net: phy: c45-tjaxx: add delay between MDIO write and read in soft_reset

commit bd1bbab upstream.

In application note (AN13663) for TJA1120, on page 30, there's a figure
with average PHY startup timing values following software reset.
The time it takes for SMI to become operational after software reset
ranges roughly from 500 us to 1500 us.

This commit adds 2000 us delay after MDIO write which triggers software
reset. Without this delay, soft_reset function returns an error and
prevents successful PHY init.

Cc: stable@vger.kernel.org
Fixes: b050f2f ("phy: nxp-c45: add driver for tja1103")
Signed-off-by: Milos Reljin <milos_reljin@outlook.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Link: https://patch.msgid.link/AM8P250MB0124D258E5A71041AF2CC322E1E32@AM8P250MB0124.EURP250.PROD.OUTLOOK.COM
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: Milos Reljin

drivers/net/phy/nxp-c45-tja11xx.c

@@ -1296,6 +1296,8 @@ static int nxp_c45_soft_reset(struct phy_device *phydev)
 	if (ret)
 		return ret;
 
+	usleep_range(2000, 2050);
+
 	return phy_read_mmd_poll_timeout(phydev, MDIO_MMD_VEND1,
 					 VEND1_DEVICE_CONTROL, ret,
 					 !(ret & DEVICE_CONTROL_RESET), 20000,