[PATCH net-next V2 10/10] net/mlx5e: Use the 'num_doorbells' devlink param

Tariq Toukan
2025-09-16T14:13:42Z

From: Cosmin Ratiu <cratiu@nvidia.com>

Use the new devlink param to control how many doorbells mlx5e devices
allocate and use. The maximum number of doorbells configurable is capped
to the maximum number of channels. This only applies to the Ethernet
part, the RDMA devices using mlx5 manage their own doorbells.

Signed-off-by: Cosmin Ratiu <cratiu@nvidia.com>
Reviewed-by: Dragos Tatulea <dtatulea@nvidia.com>
Signed-off-by: Tariq Toukan <tariqt@nvidia.com>
---
Documentation/networking/devlink/mlx5.rst | 9 +++++++
.../net/ethernet/mellanox/mlx5/core/devlink.c | 26 +++++++++++++++++++
.../ethernet/mellanox/mlx5/core/en_common.c | 15 ++++++++++-
3 files changed, 49 insertions(+), 1 deletion(-)

diff --git a/Documentation/networking/devlink/mlx5.rst b/Documentation/networking/devlink/mlx5.rst
index 60cc9fedf1ef..41c9b716699e 100644
--- a/Documentation/networking/devlink/mlx5.rst
+++ b/Documentation/networking/devlink/mlx5.rst
@@ -62,6 +62,15 @@ Note: permanent parameters such as ``enable_sriov`` and ``total_vfs`` require FW
echo 1 >/sys/bus/pci/rescan
grep ^ /sys/bus/pci/devices/0000:01:00.0/sriov_*

+ * - ``num_doorbells``
+ - driverinit
+ - This controls the number of channel doorbells used by the netdev. In all
+ cases, an additional doorbell is allocated and used for non-channel
+ communication (e.g. for PTP, HWS, etc.). Supported values are:
+
+ - 0: No channel-specific doorbells, use the global one for everything.
+ - [1, max_num_channels]: Spread netdev channels equally across these
+ doorbells.

The ``mlx5`` driver also implements the following driver-specific
parameters.
diff --git a/drivers/net/ethernet/mellanox/mlx5/core/devlink.c b/drivers/net/ethernet/mellanox/mlx5/core/devlink.c
index a0b68321355a..bd4cb8861218 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/devlink.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/devlink.c
@@ -535,6 +535,25 @@ mlx5_devlink_hairpin_queue_size_validate(struct devlink *devlink, u32 id,
return 0;
}

+static int mlx5_devlink_num_doorbells_validate(struct devlink *devlink, u32 id,
+ union devlink_param_value val,
+ struct netlink_ext_ack *extack)
+{
+ struct mlx5_core_dev *mdev = devlink_priv(devlink);
+ u32 val32 = val.vu32;
+ u32 max_num_channels;
+
+ max_num_channels = mlx5e_get_max_num_channels(mdev);
+ if (val32 > max_num_channels) {
+ NL_SET_ERR_MSG_FMT_MOD(extack,
+ "Requested num_doorbells (%u) exceeds maximum number of channels (%u)",
+ val32, max_num_channels);
+ return -EINVAL;
+ }
+
+ return 0;
+}
+
static void mlx5_devlink_hairpin_params_init_values(struct devlink *devlink)
{
struct mlx5_core_dev *dev = devlink_priv(devlink);
@@ -614,6 +633,9 @@ static const struct devlink_param mlx5_devlink_eth_params[] = {
"hairpin_queue_size", DEVLINK_PARAM_TYPE_U32,
BIT(DEVLINK_PARAM_CMODE_DRIVERINIT), NULL, NULL,
mlx5_devlink_hairpin_queue_size_validate),
+ DEVLINK_PARAM_GENERIC(NUM_DOORBELLS,
+ BIT(DEVLINK_PARAM_CMODE_DRIVERINIT), NULL, NULL,
+ mlx5_devlink_num_doorbells_validate),
};

static int mlx5_devlink_eth_params_register(struct devlink *devlink)
@@ -637,6 +659,10 @@ static int mlx5_devlink_eth_params_register(struct devlink *devlink)

mlx5_devlink_hairpin_params_init_values(devlink);

+ value.vu32 = MLX5_DEFAULT_NUM_DOORBELLS;
+ devl_param_driverinit_value_set(devlink,
+ DEVLINK_PARAM_GENERIC_ID_NUM_DOORBELLS,
+ value);
return 0;
}

diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en_common.c b/drivers/net/ethernet/mellanox/mlx5/core/en_common.c
index d13cebbc763a..96b744ceaf13 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en_common.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en_common.c
@@ -30,6 +30,7 @@
* SOFTWARE.
*/

+#include "devlink.h"
#include "en.h"
#include "lib/crypto.h"

@@ -140,6 +141,18 @@ static int mlx5e_create_tises(struct mlx5_core_dev *mdev, u32 tisn[MLX5_MAX_PORT
return err;
}

+static unsigned int
+mlx5e_get_devlink_param_num_doorbells(struct mlx5_core_dev *dev)
+{
+ const u32 param_id = DEVLINK_PARAM_GENERIC_ID_NUM_DOORBELLS;
+ struct devlink *devlink = priv_to_devlink(dev);
+ union devlink_param_value val;
+ int err;
+
+ err = devl_param_driverinit_value_get(devlink, param_id, &val);
+ return err ? MLX5_DEFAULT_NUM_DOORBELLS : val.vu32;
+}
+
int mlx5e_create_mdev_resources(struct mlx5_core_dev *mdev, bool create_tises)
{
struct mlx5e_hw_objs *res = &mdev->mlx5e_res.hw_objs;
@@ -164,7 +177,7 @@ int mlx5e_create_mdev_resources(struct mlx5_core_dev *mdev, bool create_tises)
goto err_dealloc_transport_domain;
}

- num_doorbells = min(MLX5_DEFAULT_NUM_DOORBELLS,
+ num_doorbells = min(mlx5e_get_devlink_param_num_doorbells(mdev),
mlx5e_get_max_num_channels(mdev));
res->bfregs = kcalloc(num_doorbells, sizeof(*res->bfregs), GFP_KERNEL);
if (!res->bfregs) {
--
2.31.1