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From: Horatiu Vultur <horatiu.vultur@microchip.com>
To: <andrew@lunn.ch>, <hkallweit1@gmail.com>, <linux@armlinux.org.uk>,
	<davem@davemloft.net>, <edumazet@google.com>, <kuba@kernel.org>,
	<pabeni@redhat.com>
CC: <netdev@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
	<UNGLinuxDriver@microchip.com>, Horatiu Vultur <horatiu.vultur@microchip.com>
Subject: [PATCH net-next] net: micrel: Fix the frequency adjustments
Date: Thu, 1 Feb 2024 21:42:03 +0100
Message-ID: <20240201204203.2691424-1-horatiu.vultur@microchip.com>
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By default lan8841's 1588 clock frequency is 125MHz. But when adjusting
the frequency, it is using the 1PPM format of the lan8814. Which is the
wrong format as lan8814 has a 1588 clock frequency of 250MHz. So then
for each 1PPM adjustment would adjust less than expected.
Therefore fix this by using the correct 1PPM format for lan8841.

Signed-off-by: Horatiu Vultur <horatiu.vultur@microchip.com>
---
 drivers/net/phy/micrel.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/drivers/net/phy/micrel.c b/drivers/net/phy/micrel.c
index 40bea9293ddd7..9b69735819896 100644
--- a/drivers/net/phy/micrel.c
+++ b/drivers/net/phy/micrel.c
@@ -120,6 +120,12 @@
  */
 #define LAN8814_1PPM_FORMAT			17179
 
+/* Represents 1ppm adjustment in 2^32 format with
+ * each nsec contains 8 clock cycles.
+ * The value is calculated as following: (1/1000000)/((2^-32)/8)
+ */
+#define LAN8841_1PPM_FORMAT			34360
+
 #define PTP_RX_VERSION				0x0248
 #define PTP_TX_VERSION				0x0288
 #define PTP_MAX_VERSION(x)			(((x) & GENMASK(7, 0)) << 8)
@@ -4115,8 +4121,8 @@ static int lan8841_ptp_adjfine(struct ptp_clock_info *ptp, long scaled_ppm)
 		faster = false;
 	}
 
-	rate = LAN8814_1PPM_FORMAT * (upper_16_bits(scaled_ppm));
-	rate += (LAN8814_1PPM_FORMAT * (lower_16_bits(scaled_ppm))) >> 16;
+	rate = LAN8841_1PPM_FORMAT * (upper_16_bits(scaled_ppm));
+	rate += (LAN8841_1PPM_FORMAT * (lower_16_bits(scaled_ppm))) >> 16;
 
 	mutex_lock(&ptp_priv->ptp_lock);
 	phy_write_mmd(phydev, 2, LAN8841_PTP_LTC_RATE_ADJ_HI,
-- 
2.34.1