netdev - [PATCH net 2/3] mlxsw: core_env: Fix driver initialization with old firmware

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Message-ID: <314f08cecbcae00340390e077cf20e02d0b48446.1713262810.git.petrm@nvidia.com>
Date: Tue, 16 Apr 2024 12:24:15 +0200
From: Petr Machata <petrm@...dia.com>
To: "David S. Miller" <davem@...emloft.net>, Eric Dumazet
	<edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni
	<pabeni@...hat.com>, <netdev@...r.kernel.org>
CC: Ido Schimmel <idosch@...dia.com>, Petr Machata <petrm@...dia.com>,
	<mlxsw@...dia.com>, Tim 'mithro' Ansell <me@...h.ro>
Subject: [PATCH net 2/3] mlxsw: core_env: Fix driver initialization with old firmware

From: Ido Schimmel <idosch@...dia.com>

The driver queries the Management Capabilities Mask (MCAM) register
during initialization to understand if it can read up to 128 bytes from
transceiver modules.

However, not all firmware versions support this register, leading to the
driver failing to load.

Fix by treating an error in the register query as an indication that the
feature is not supported.

Fixes: 1f4aea1f72da ("mlxsw: core_env: Read transceiver module EEPROM in 128 bytes chunks")
Reported-by: Tim 'mithro' Ansell <me@...h.ro>
Signed-off-by: Ido Schimmel <idosch@...dia.com>
Reviewed-by: Petr Machata <petrm@...dia.com>
Signed-off-by: Petr Machata <petrm@...dia.com>
---
 drivers/net/ethernet/mellanox/mlxsw/core_env.c | 10 ++++------
 1 file changed, 4 insertions(+), 6 deletions(-)

diff --git a/drivers/net/ethernet/mellanox/mlxsw/core_env.c b/drivers/net/ethernet/mellanox/mlxsw/core_env.c
index 53b150b7ae4e..5d02b6aef4d2 100644
--- a/drivers/net/ethernet/mellanox/mlxsw/core_env.c
+++ b/drivers/net/ethernet/mellanox/mlxsw/core_env.c
@@ -1360,17 +1360,15 @@ static struct mlxsw_linecards_event_ops mlxsw_env_event_ops = {
 static int mlxsw_env_max_module_eeprom_len_query(struct mlxsw_env *mlxsw_env)
 {
 	char mcam_pl[MLXSW_REG_MCAM_LEN];
-	bool mcia_128b_supported;
+	bool mcia_128b_supported = false;
 	int err;
 
 	mlxsw_reg_mcam_pack(mcam_pl,
 			    MLXSW_REG_MCAM_FEATURE_GROUP_ENHANCED_FEATURES);
 	err = mlxsw_reg_query(mlxsw_env->core, MLXSW_REG(mcam), mcam_pl);
-	if (err)
-		return err;
-
-	mlxsw_reg_mcam_unpack(mcam_pl, MLXSW_REG_MCAM_MCIA_128B,
-			      &mcia_128b_supported);
+	if (!err)
+		mlxsw_reg_mcam_unpack(mcam_pl, MLXSW_REG_MCAM_MCIA_128B,
+				      &mcia_128b_supported);
 
 	mlxsw_env->max_eeprom_len = mcia_128b_supported ? 128 : 48;
 
-- 
2.43.0