linux-kernel - [PATCH v2] net: phy: c45-tjaxx: add delay between MDIO write and read in soft

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Message-ID:
 <AM8P250MB0124B5051DF9B54EC325644CE1E02@AM8P250MB0124.EURP250.PROD.OUTLOOK.COM>
Date: Thu, 23 Jan 2025 15:43:46 +0000
From: Milos Reljin <milos_reljin@...look.com>
To: andrei.botila@....nxp.com, andrew@...n.ch, hkallweit1@...il.com,
	linux@...linux.org.uk, davem@...emloft.net, edumazet@...gle.com,
	kuba@...nel.org, pabeni@...hat.com, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Cc: milos.reljin@...rk.com
Subject: [PATCH v2] net: phy: c45-tjaxx: add delay between MDIO write and
 read in soft_reset

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.

Signed-off-by: Milos Reljin <milos_reljin@...look.com>
---
Changes in v2:
 - Updated commit message to clear up where the delay value comes from.
 - Delay added with usleep_range instead of changing sleep_before_read
   parameter of phy_read_mmd_poll_timeout to avoid excessive delay.
---
 drivers/net/phy/nxp-c45-tja11xx.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/net/phy/nxp-c45-tja11xx.c b/drivers/net/phy/nxp-c45-tja11xx.c
index ade544bc007d..872e582b7e83 100644
--- a/drivers/net/phy/nxp-c45-tja11xx.c
+++ b/drivers/net/phy/nxp-c45-tja11xx.c
@@ -1297,6 +1297,8 @@ 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,
-- 
2.34.1