net/mlx5: Let user configure event_eq_size param

Event EQ is an EQ which received the notification of almost all the
events generated by the NIC.
Currently, each event EQ is taking 512KB of memory. This size is not
needed in most use cases, and is critical with large scale. Hence,
allow user to configure the size of the event EQ.

For example to reduce event EQ size to 64, execute::
$ devlink dev param set pci/0000:00:0b.0 name event_eq_size value 64 \
cmode driverinit
$ devlink dev reload pci/0000:00:0b.0

Signed-off-by: Shay Drory <[e-mail]>
Reviewed-by: Moshe Shemesh <[e-mail]>
Signed-off-by: Saeed Mahameed <[e-mail]>

Documentation/networking/devlink/mlx5.rst

···
    * - ``io_eq_size``
      - driverinit
      - The range is between 64 and 4096.
+   * - ``event_eq_size``
+     - driverinit
+     - The range is between 64 and 4096.
 
 The ``mlx5`` driver also implements the following driver-specific
 parameters.

drivers/net/ethernet/mellanox/mlx5/core/devlink.c

···
 			      mlx5_devlink_enable_remote_dev_reset_set, NULL),
 	DEVLINK_PARAM_GENERIC(IO_EQ_SIZE, BIT(DEVLINK_PARAM_CMODE_DRIVERINIT),
 			      NULL, NULL, mlx5_devlink_eq_depth_validate),
+	DEVLINK_PARAM_GENERIC(EVENT_EQ_SIZE, BIT(DEVLINK_PARAM_CMODE_DRIVERINIT),
+			      NULL, NULL, mlx5_devlink_eq_depth_validate),
 };
 
 static void mlx5_devlink_set_params_init_values(struct devlink *devlink)
···
 	value.vu32 = MLX5_COMP_EQ_SIZE;
 	devlink_param_driverinit_value_set(devlink,
 					   DEVLINK_PARAM_GENERIC_ID_IO_EQ_SIZE,
+					   value);
+
+	value.vu32 = MLX5_NUM_ASYNC_EQE;
+	devlink_param_driverinit_value_set(devlink,
+					   DEVLINK_PARAM_GENERIC_ID_EVENT_EQ_SIZE,
 					   value);
 }
 

drivers/net/ethernet/mellanox/mlx5/core/eq.c

···
 			      name, err);
 }
 
+static u16 async_eq_depth_devlink_param_get(struct mlx5_core_dev *dev)
+{
+	struct devlink *devlink = priv_to_devlink(dev);
+	union devlink_param_value val;
+	int err;
+
+	err = devlink_param_driverinit_value_get(devlink,
+						 DEVLINK_PARAM_GENERIC_ID_EVENT_EQ_SIZE,
+						 &val);
+	if (!err)
+		return val.vu32;
+	mlx5_core_dbg(dev, "Failed to get param. using default. err = %d\n", err);
+	return MLX5_NUM_ASYNC_EQE;
+}
 static int create_async_eqs(struct mlx5_core_dev *dev)
 {
 	struct mlx5_eq_table *table = dev->priv.eq_table;
···
 
 	param = (struct mlx5_eq_param) {
 		.irq_index = MLX5_IRQ_EQ_CTRL,
-		.nent = MLX5_NUM_ASYNC_EQE,
+		.nent = async_eq_depth_devlink_param_get(dev),
 	};
 
 	gather_async_events_mask(dev, param.mask);