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net: dsa: microchip: use collision based back pressure mode

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[ Upstream commit d963c95bc9840d070a788c35e41b715a648717f7 ]

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@savoirfairelinux.com>
Reviewed-by: Woojung Huh <Woojung.huh@microchip.com>
Acked-by: Arun Ramadoss <arun.ramadoss@microchip.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Enguerrand de Ribaucourt 2024-06-21 16:43:21 +02:00 committed by Greg Kroah-Hartman
parent 96c8693fc1
commit 9d36f6312b
2 changed files with 5 additions and 0 deletions
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4
drivers/net/dsa/microchip/ksz9477.c
View File

@ -1112,6 +1112,10 @@ 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);

1
drivers/net/dsa/microchip/ksz9477_reg.h
View File

@ -267,6 +267,7 @@
#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)