[RFC net-next 4/4] net/mlx5e: Implement set_module_eeprom_by_page ethtool callback

["Björn Töpel" <bjorn@kernel.org>]

Add EEPROM write support by implementing the set_module_eeprom_by_page
ethtool_ops callback, mirroring the existing get_module_eeprom_by_page
read path. This enables the kernel's module loopback SET path which
requires both get and set callbacks.

The write path reuses the MCIA register (MLX5_REG_MCIA) via
mlx5_core_access_reg() with write=1 instead of write=0.

This seems to work, but I'd like some proper feedback from the mlx5
folks! ;-)

Signed-off-by: Björn Töpel <bjorn@kernel.org>
---
 .../ethernet/mellanox/mlx5/core/en_ethtool.c  | 52 +++++++++++++------
 .../ethernet/mellanox/mlx5/core/mlx5_core.h   |  6 +--
 .../net/ethernet/mellanox/mlx5/core/port.c    | 34 ++++++++----
 3 files changed, 64 insertions(+), 28 deletions(-)

diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en_ethtool.c b/drivers/net/ethernet/mellanox/mlx5/core/en_ethtool.c
index 4a8dc85d5924..1dce67485651 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en_ethtool.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en_ethtool.c
@@ -2103,22 +2103,24 @@ static int mlx5e_get_module_eeprom(struct net_device *netdev,
 	return 0;
 }
 
-static int mlx5e_get_module_eeprom_by_page(struct net_device *netdev,
-					   const struct ethtool_module_eeprom *page_data,
-					   struct netlink_ext_ack *extack)
+static int __mlx5e_access_module_eeprom_by_page(struct net_device *netdev,
+						const struct ethtool_module_eeprom *page_data,
+						struct netlink_ext_ack *extack,
+						bool write)
 {
 	struct mlx5e_priv *priv = netdev_priv(netdev);
 	struct mlx5_module_eeprom_query_params query;
 	struct mlx5_core_dev *mdev = priv->mdev;
 	u8 *data = page_data->data;
-	int size_read;
+	int size_xfered;
 	u8 status = 0;
 	int i = 0;
 
 	if (!page_data->length)
 		return -EINVAL;
 
-	memset(data, 0, page_data->length);
+	if (!write)
+		memset(data, 0, page_data->length);
 
 	query.offset = page_data->offset;
 	query.i2c_address = page_data->i2c_address;
@@ -2126,28 +2128,47 @@ static int mlx5e_get_module_eeprom_by_page(struct net_device *netdev,
 	query.page = page_data->page;
 	while (i < page_data->length) {
 		query.size = page_data->length - i;
-		size_read = mlx5_query_module_eeprom_by_page(mdev, &query,
-							     data + i, &status);
+		size_xfered = mlx5_access_module_eeprom_by_page(mdev, &query,
+								data + i, &status,
+								write);
 
-		/* Done reading, return how many bytes was read */
-		if (!size_read)
+		if (!size_xfered)
 			return i;
 
-		if (size_read < 0) {
+		if (size_xfered < 0) {
 			NL_SET_ERR_MSG_FMT_MOD(
 				extack,
-				"Query module eeprom by page failed, read %u bytes, err %d, status %u",
-				i, size_read, status);
-			return size_read;
+				"%s module eeprom by page failed, %s %u bytes, err %d, status %u",
+				write ? "Set" : "Query",
+				write ? "wrote" : "read",
+				i, size_xfered, status);
+			return size_xfered;
 		}
 
-		i += size_read;
-		query.offset += size_read;
+		i += size_xfered;
+		query.offset += size_xfered;
 	}
 
 	return i;
 }
 
+static int mlx5e_get_module_eeprom_by_page(struct net_device *netdev,
+					   const struct ethtool_module_eeprom *page_data,
+					   struct netlink_ext_ack *extack)
+{
+	return __mlx5e_access_module_eeprom_by_page(netdev, page_data, extack, false);
+}
+
+static int mlx5e_set_module_eeprom_by_page(struct net_device *netdev,
+					   const struct ethtool_module_eeprom *page_data,
+					   struct netlink_ext_ack *extack)
+{
+	int err;
+
+	err = __mlx5e_access_module_eeprom_by_page(netdev, page_data, extack, true);
+	return err < 0 ? err : 0;
+}
+
 int mlx5e_ethtool_flash_device(struct mlx5e_priv *priv,
 			       struct ethtool_flash *flash)
 {
@@ -2776,6 +2797,7 @@ const struct ethtool_ops mlx5e_ethtool_ops = {
 	.get_module_info   = mlx5e_get_module_info,
 	.get_module_eeprom = mlx5e_get_module_eeprom,
 	.get_module_eeprom_by_page = mlx5e_get_module_eeprom_by_page,
+	.set_module_eeprom_by_page = mlx5e_set_module_eeprom_by_page,
 	.flash_device      = mlx5e_flash_device,
 	.get_priv_flags    = mlx5e_get_priv_flags,
 	.set_priv_flags    = mlx5e_set_priv_flags,
diff --git a/drivers/net/ethernet/mellanox/mlx5/core/mlx5_core.h b/drivers/net/ethernet/mellanox/mlx5/core/mlx5_core.h
index b635b423d972..b69730727764 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/mlx5_core.h
+++ b/drivers/net/ethernet/mellanox/mlx5/core/mlx5_core.h
@@ -361,9 +361,9 @@ void mlx5_query_port_fcs(struct mlx5_core_dev *mdev, bool *supported,
 int mlx5_query_module_eeprom(struct mlx5_core_dev *dev,
 			     u16 offset, u16 size, u8 *data, u8 *status);
 int
-mlx5_query_module_eeprom_by_page(struct mlx5_core_dev *dev,
-				 struct mlx5_module_eeprom_query_params *params,
-				 u8 *data, u8 *status);
+mlx5_access_module_eeprom_by_page(struct mlx5_core_dev *dev,
+				  struct mlx5_module_eeprom_query_params *params,
+				  u8 *data, u8 *status, bool write);
 
 int mlx5_query_port_dcbx_param(struct mlx5_core_dev *mdev, u32 *out);
 int mlx5_set_port_dcbx_param(struct mlx5_core_dev *mdev, u32 *in);
diff --git a/drivers/net/ethernet/mellanox/mlx5/core/port.c b/drivers/net/ethernet/mellanox/mlx5/core/port.c
index ee8b9765c5ba..d68f9f9d7a80 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/port.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/port.c
@@ -369,9 +369,9 @@ static int mlx5_mcia_max_bytes(struct mlx5_core_dev *dev)
 	return (MLX5_CAP_MCAM_FEATURE(dev, mcia_32dwords) ? 32 : 12) * sizeof(u32);
 }
 
-static int mlx5_query_mcia(struct mlx5_core_dev *dev,
-			   struct mlx5_module_eeprom_query_params *params,
-			   u8 *data, u8 *status)
+static int __mlx5_access_mcia(struct mlx5_core_dev *dev,
+			      struct mlx5_module_eeprom_query_params *params,
+			      u8 *data, u8 *status, bool write)
 {
 	u32 in[MLX5_ST_SZ_DW(mcia_reg)] = {};
 	u32 out[MLX5_ST_SZ_DW(mcia_reg)];
@@ -388,8 +388,13 @@ static int mlx5_query_mcia(struct mlx5_core_dev *dev,
 	MLX5_SET(mcia_reg, in, page_number, params->page);
 	MLX5_SET(mcia_reg, in, i2c_device_address, params->i2c_address);
 
+	if (write) {
+		ptr = MLX5_ADDR_OF(mcia_reg, in, dword_0);
+		memcpy(ptr, data, size);
+	}
+
 	err = mlx5_core_access_reg(dev, in, sizeof(in), out,
-				   sizeof(out), MLX5_REG_MCIA, 0, 0);
+				   sizeof(out), MLX5_REG_MCIA, 0, write);
 	if (err)
 		return err;
 
@@ -399,12 +404,21 @@ static int mlx5_query_mcia(struct mlx5_core_dev *dev,
 		return -EIO;
 	}
 
-	ptr = MLX5_ADDR_OF(mcia_reg, out, dword_0);
-	memcpy(data, ptr, size);
+	if (!write) {
+		ptr = MLX5_ADDR_OF(mcia_reg, out, dword_0);
+		memcpy(data, ptr, size);
+	}
 
 	return size;
 }
 
+static int mlx5_query_mcia(struct mlx5_core_dev *dev,
+			   struct mlx5_module_eeprom_query_params *params,
+			   u8 *data, u8 *status)
+{
+	return __mlx5_access_mcia(dev, params, data, status, false);
+}
+
 int mlx5_query_module_eeprom(struct mlx5_core_dev *dev,
 			     u16 offset, u16 size, u8 *data, u8 *status)
 {
@@ -446,9 +460,9 @@ int mlx5_query_module_eeprom(struct mlx5_core_dev *dev,
 	return mlx5_query_mcia(dev, &query, data, status);
 }
 
-int mlx5_query_module_eeprom_by_page(struct mlx5_core_dev *dev,
-				     struct mlx5_module_eeprom_query_params *params,
-				     u8 *data, u8 *status)
+int mlx5_access_module_eeprom_by_page(struct mlx5_core_dev *dev,
+				      struct mlx5_module_eeprom_query_params *params,
+				      u8 *data, u8 *status, bool write)
 {
 	int err;
 
@@ -462,7 +476,7 @@ int mlx5_query_module_eeprom_by_page(struct mlx5_core_dev *dev,
 		return -EINVAL;
 	}
 
-	return mlx5_query_mcia(dev, params, data, status);
+	return __mlx5_access_mcia(dev, params, data, status, write);
 }
 
 static int mlx5_query_port_pvlc(struct mlx5_core_dev *dev, u32 *pvlc,
-- 
2.53.0