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Message-Id: <20240604092304.314636-4-enguerrand.de-ribaucourt@savoirfairelinux.com>
Date: Tue, 4 Jun 2024 09:23:04 +0000
From: Enguerrand de Ribaucourt <enguerrand.de-ribaucourt@...oirfairelinux.com>
To: netdev@...r.kernel.org
Cc: andrew@...n.ch,
hkallweit1@...il.com,
linux@...linux.org.uk,
woojung.huh@...rochip.com,
UNGLinuxDriver@...rochip.com,
horms@...nel.org,
Tristram.Ha@...rochip.com,
Arun.Ramadoss@...rochip.com,
Enguerrand de Ribaucourt <enguerrand.de-ribaucourt@...oirfairelinux.com>
Subject: [PATCH net v5 3/4] net: dsa: microchip: use collision based back pressure mode
Errata DS80000758 states that carrier sense back pressure mode can cause
link down issues in 100BASE-TX half duplex mode. The datasheet also
recommends to always use the collision based back pressure mode.
Fixes: b987e98e50ab ("dsa: add DSA switch driver for Microchip KSZ9477")
Signed-off-by: Enguerrand de Ribaucourt <enguerrand.de-ribaucourt@...oirfairelinux.com>
---
v5:
- define SW_BACK_PRESSURE_COLLISION
v4: https://lore.kernel.org/all/20240531142430.678198-5-enguerrand.de-ribaucourt@savoirfairelinux.com/
- rebase on net/main
- add Fixes tag
v3: https://lore.kernel.org/all/20240530102436.226189-5-enguerrand.de-ribaucourt@savoirfairelinux.com/
---
drivers/net/dsa/microchip/ksz9477.c | 4 ++++
drivers/net/dsa/microchip/ksz9477_reg.h | 1 +
2 files changed, 5 insertions(+)
diff --git a/drivers/net/dsa/microchip/ksz9477.c b/drivers/net/dsa/microchip/ksz9477.c
index f8ad7833f5d9..c2878dd0ad7e 100644
--- a/drivers/net/dsa/microchip/ksz9477.c
+++ b/drivers/net/dsa/microchip/ksz9477.c
@@ -1299,6 +1299,10 @@ int ksz9477_setup(struct dsa_switch *ds)
/* Enable REG_SW_MTU__2 reg by setting SW_JUMBO_PACKET */
ksz_cfg(dev, REG_SW_MAC_CTRL_1, SW_JUMBO_PACKET, true);
+ /* Use collision based back pressure mode. */
+ ksz_cfg(dev, REG_SW_MAC_CTRL_1, SW_BACK_PRESSURE,
+ SW_BACK_PRESSURE_COLLISION);
+
/* Now we can configure default MTU value */
ret = regmap_update_bits(ksz_regmap_16(dev), REG_SW_MTU__2, REG_SW_MTU_MASK,
VLAN_ETH_FRAME_LEN + ETH_FCS_LEN);
diff --git a/drivers/net/dsa/microchip/ksz9477_reg.h b/drivers/net/dsa/microchip/ksz9477_reg.h
index f3a205ee483f..fb124be8edd3 100644
--- a/drivers/net/dsa/microchip/ksz9477_reg.h
+++ b/drivers/net/dsa/microchip/ksz9477_reg.h
@@ -247,6 +247,7 @@
#define REG_SW_MAC_CTRL_1 0x0331
#define SW_BACK_PRESSURE BIT(5)
+#define SW_BACK_PRESSURE_COLLISION 0
#define FAIR_FLOW_CTRL BIT(4)
#define NO_EXC_COLLISION_DROP BIT(3)
#define SW_JUMBO_PACKET BIT(2)
--
2.34.1
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