mlxsw: spectrum: Upper-bound supported FW version

During initialization the driver checks whether the flashed FW image
suits its requirements by checking that it's sufficiently new.
However, there's only a weak backward compatibility scheme that is
actually guaranteed by the FW, so driver must also upper bound the
version to prevent compatibility issues between current driver and some
possible future fw.
Signed-off-by: Yuval Mintz <yuvalm@mellanox.com>
Reviewed-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/mellanox/mlxsw/spectrum.c

@@ -76,12 +76,7 @@
 #define MLXSW_FWREV_MAJOR 13
 #define MLXSW_FWREV_MINOR 1530
 #define MLXSW_FWREV_SUBMINOR 152
-
-static const struct mlxsw_fw_rev mlxsw_sp_supported_fw_rev = {
-	.major = MLXSW_FWREV_MAJOR,
-	.minor = MLXSW_FWREV_MINOR,
-	.subminor = MLXSW_FWREV_SUBMINOR
-};
+#define MLXSW_FWREV_MINOR_TO_BRANCH(minor) ((minor) / 100)
 
 #define MLXSW_SP_FW_FILENAME \
 	"mellanox/mlxsw_spectrum-" __stringify(MLXSW_FWREV_MAJOR) \
@@ -339,28 +334,25 @@ static int mlxsw_sp_firmware_flash(struct mlxsw_sp *mlxsw_sp,
 	return mlxfw_firmware_flash(&mlxsw_sp_mlxfw_dev.mlxfw_dev, firmware);
 }
 
-static bool mlxsw_sp_fw_rev_ge(const struct mlxsw_fw_rev *a,
-			       const struct mlxsw_fw_rev *b)
-{
-	if (a->major != b->major)
-		return a->major > b->major;
-	if (a->minor != b->minor)
-		return a->minor > b->minor;
-	return a->subminor >= b->subminor;
-}
-
 static int mlxsw_sp_fw_rev_validate(struct mlxsw_sp *mlxsw_sp)
 {
 	const struct mlxsw_fw_rev *rev = &mlxsw_sp->bus_info->fw_rev;
 	const struct firmware *firmware;
 	int err;
 
-	if (mlxsw_sp_fw_rev_ge(rev, &mlxsw_sp_supported_fw_rev))
+	/* Validate driver & FW are compatible */
+	if (rev->major != MLXSW_FWREV_MAJOR) {
+		WARN(1, "Mismatch in major FW version [%d:%d] is never expected; Please contact support\n",
+		     rev->major, MLXSW_FWREV_MAJOR);
+		return -EINVAL;
+	}
+	if (MLXSW_FWREV_MINOR_TO_BRANCH(rev->minor) ==
+	    MLXSW_FWREV_MINOR_TO_BRANCH(MLXSW_FWREV_MINOR))
 		return 0;
 
-	dev_info(mlxsw_sp->bus_info->dev, "The firmware version %d.%d.%d is out of date\n",
+	dev_info(mlxsw_sp->bus_info->dev, "The firmware version %d.%d.%d is incompatible with the driver\n",
 		 rev->major, rev->minor, rev->subminor);
-	dev_info(mlxsw_sp->bus_info->dev, "Upgrading firmware using file %s\n",
+	dev_info(mlxsw_sp->bus_info->dev, "Flashing firmware using file %s\n",
 		 MLXSW_SP_FW_FILENAME);
 
 	err = request_firmware_direct(&firmware, MLXSW_SP_FW_FILENAME,