linux-kernel - [PATCH net-next 2/2] net: phy: micrel: lan8814 cable improvement errata

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Date: Wed, 28 Feb 2024 07:28:13 +0100
From: Horatiu Vultur <horatiu.vultur@...rochip.com>
To: <andrew@...n.ch>, <hkallweit1@...il.com>, <linux@...linux.org.uk>,
	<davem@...emloft.net>, <edumazet@...gle.com>, <kuba@...nel.org>,
	<pabeni@...hat.com>
CC: <netdev@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<UNGLinuxDriver@...rochip.com>, Horatiu Vultur <horatiu.vultur@...rochip.com>
Subject: [PATCH net-next 2/2] net: phy: micrel: lan8814 cable improvement errata

When the length of the cable is more than 100m and the lan8814 is
configured to run in 1000Base-T Slave then the register of the device
needs to be optimized.

Workaround this by setting the measure time to a value of 0xb. This
value can be set regardless of the configuration.

This issue is described in 'LAN8814 Silicon Errata and Data Sheet
Clarification' and according to that, this will not be corrected in a
future silicon revision.

Signed-off-by: Horatiu Vultur <horatiu.vultur@...rochip.com>
---
 drivers/net/phy/micrel.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/drivers/net/phy/micrel.c b/drivers/net/phy/micrel.c
index 5a0cc89eaebdd..1e3b0436e161e 100644
--- a/drivers/net/phy/micrel.c
+++ b/drivers/net/phy/micrel.c
@@ -117,6 +117,10 @@
 #define LAN8814_EEE_STATE			0x38
 #define LAN8814_EEE_STATE_MASK2P5P		BIT(10)
 
+#define LAN8814_PD_CONTROLS			0x9d
+#define LAN8814_PD_CONTROLS_PD_MEAS_TIME_MASK_	GENMASK(3, 0)
+#define LAN8814_PD_CONTROLS_PD_MEAS_TIME_VAL_	0xb
+
 /* Represents 1ppm adjustment in 2^32 format with
  * each nsec contains 4 clock cycles.
  * The value is calculated as following: (1/1000000)/((2^-32)/4)
@@ -3302,6 +3306,12 @@ static void lan8814_errata_fixes(struct phy_device *phydev)
 	val = lanphy_read_page_reg(phydev, 2, LAN8814_EEE_STATE);
 	val &= ~LAN8814_EEE_STATE_MASK2P5P;
 	lanphy_write_page_reg(phydev, 2, LAN8814_EEE_STATE, val);
+
+	/* Improve cable reach beyond 100m */
+	val = lanphy_read_page_reg(phydev, 1, LAN8814_PD_CONTROLS);
+	val &= ~LAN8814_PD_CONTROLS_PD_MEAS_TIME_MASK_;
+	val |= LAN8814_PD_CONTROLS_PD_MEAS_TIME_VAL_;
+	lanphy_write_page_reg(phydev, 1, LAN8814_PD_CONTROLS, val);
 }
 
 static int lan8814_probe(struct phy_device *phydev)
-- 
2.34.1