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From e5aa46ceca003444bd2e7a5f4fd43d5e61499515 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Marek=20Beh=C3=BAn?= <kabel@kernel.org>
Date: Wed, 17 Aug 2022 14:35:59 +0200
Subject: [PATCH 95/96] phy: marvell: phy-mvebu-a3700-comphy: Change 2500base-x
transmit amplitude
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
Change transmit amplitude to 1025 mV for 2500base-x mode.
This fixes issue wherein if the 8b/10b encoded packet contains a long
enough alternating sequence of bits (010101... or 101010...), which
happens if the packet contains a sequence of 'J' or '\xb5' bytes, the
packet may be lost due to FCS error. The probability of loss grows with
the number of 'J's with default transmit amplitude setting - with 114
'J's the probability is about 50%, with 125 'J's almost 100% of packets
are lost.
Signed-off-by: Marek Behún <kabel@kernel.org>
---
drivers/phy/marvell/phy-mvebu-a3700-comphy.c | 18 ++++++++++++++++++
1 file changed, 18 insertions(+)
diff --git a/drivers/phy/marvell/phy-mvebu-a3700-comphy.c b/drivers/phy/marvell/phy-mvebu-a3700-comphy.c
index a4d7d9bd100d..4a18f9ca6d25 100644
--- a/drivers/phy/marvell/phy-mvebu-a3700-comphy.c
+++ b/drivers/phy/marvell/phy-mvebu-a3700-comphy.c
@@ -68,6 +68,12 @@
#define SPEED_PLL_MASK GENMASK(7, 2)
#define SPEED_PLL_VALUE_16 FIELD_PREP(SPEED_PLL_MASK, 0x10)
+#define COMPHY_GEN3_SET0 0x0d
+#define Gx_TX_AMP_MASK GENMASK(5, 1)
+#define Gx_TX_AMP_VALUE(x) FIELD_PREP(Gx_TX_AMP_MASK, x)
+#define Gx_TX_AMP_ADJ BIT(6)
+#define Gx_TX_AMP_1025MV (Gx_TX_AMP_VALUE(0x12) | Gx_TX_AMP_ADJ)
+
#define COMPHY_DIG_LOOPBACK_EN 0x23
#define SEL_DATA_WIDTH_MASK GENMASK(11, 10)
#define DATA_WIDTH_10BIT FIELD_PREP(SEL_DATA_WIDTH_MASK, 0x0)
@@ -746,6 +752,18 @@ mvebu_a3700_comphy_ethernet_power_on(struct mvebu_a3700_comphy_lane *lane)
comphy_gbe_phy_init(lane,
lane->submode != PHY_INTERFACE_MODE_2500BASEX);
+ /*
+ * Fix issue wherein a packet may be lost if it contains a long enough
+ * sequence of 'J' or '\xb5' bytes.
+ * This only happens with 2500base-x mode. Fix this by changing transmit
+ * amplitude to 1025 mV.
+ */
+ if (lane->submode == PHY_INTERFACE_MODE_2500BASEX) {
+ data = Gx_TX_AMP_1025MV;
+ mask = Gx_TX_AMP_MASK | Gx_TX_AMP_ADJ;
+ comphy_lane_reg_set(lane, COMPHY_GEN3_SET0, data, mask);
+ }
+
/*
* 14. Check the PHY Polarity invert bit
*/
--
2.37.2
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