net/mlx5e: Don't treat small ceil values as unlimited in HTB offload

commit 736dfe4 upstream.

The hardware spec defines max_average_bw == 0 as "unlimited bandwidth".
max_average_bw is calculated as `ceil / BYTES_IN_MBIT`, which can become
0 when ceil is small, leading to an undesired effect of having no
bandwidth limit.

This commit fixes it by rounding up small values of ceil to 1 Mbit/s.

Fixes: 214baf2 ("net/mlx5e: Support HTB offload")
Signed-off-by: Maxim Mikityanskiy <maximmi@nvidia.com>
Reviewed-by: Tariq Toukan <tariqt@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/net/ethernet/mellanox/mlx5/core/en/qos.c

@@ -553,7 +553,8 @@ static int mlx5e_htb_convert_rate(struct mlx5e_priv *priv, u64 rate,
 
 static void mlx5e_htb_convert_ceil(struct mlx5e_priv *priv, u64 ceil, u32 *max_average_bw)
 {
-	*max_average_bw = div_u64(ceil, BYTES_IN_MBIT);
+	/* Hardware treats 0 as "unlimited", set at least 1. */
+	*max_average_bw = max_t(u32, div_u64(ceil, BYTES_IN_MBIT), 1);
 
 	qos_dbg(priv->mdev, "Convert: ceil %llu -> max_average_bw %u\n",
 		ceil, *max_average_bw);