netdev - Re: [PATCH net-next] amd-xgbe: Configure and retrieve 'tx-usecs' for Tx coalescing

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Message-ID: <1c1e7c9c-5143-43e9-a40b-42dfc3866a56@linux.dev>
Date: Mon, 16 Jun 2025 12:29:40 +0100
From: Vadim Fedorenko <vadim.fedorenko@...ux.dev>
To: Vishal Badole <Vishal.Badole@....com>, Shyam-sundar.S-k@....com,
 andrew+netdev@...n.ch, davem@...emloft.net, edumazet@...gle.com,
 kuba@...nel.org, pabeni@...hat.com, netdev@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next] amd-xgbe: Configure and retrieve 'tx-usecs' for
 Tx coalescing

On 16/06/2025 11:42, Vishal Badole wrote:
> Ethtool has advanced with additional configurable options, but the
> current driver does not support tx-usecs configuration.
> 
> Add support to configure and retrieve 'tx-usecs' using ethtool, which
> specifies the wait time before servicing an interrupt for Tx coalescing.
> 
> Signed-off-by: Vishal Badole <Vishal.Badole@....com>
> Acked-by: Shyam Sundar S K <Shyam-sundar.S-k@....com>
> ---
>   drivers/net/ethernet/amd/xgbe/xgbe-ethtool.c | 19 +++++++++++++++++--
>   drivers/net/ethernet/amd/xgbe/xgbe.h         |  1 +
>   2 files changed, 18 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/ethernet/amd/xgbe/xgbe-ethtool.c b/drivers/net/ethernet/amd/xgbe/xgbe-ethtool.c
> index 12395428ffe1..362f8623433a 100644
> --- a/drivers/net/ethernet/amd/xgbe/xgbe-ethtool.c
> +++ b/drivers/net/ethernet/amd/xgbe/xgbe-ethtool.c
> @@ -450,6 +450,7 @@ static int xgbe_get_coalesce(struct net_device *netdev,
>   	ec->rx_coalesce_usecs = pdata->rx_usecs;
>   	ec->rx_max_coalesced_frames = pdata->rx_frames;
>   
> +	ec->tx_coalesce_usecs = pdata->tx_usecs;
>   	ec->tx_max_coalesced_frames = pdata->tx_frames;
>   
>   	return 0;
> @@ -463,7 +464,7 @@ static int xgbe_set_coalesce(struct net_device *netdev,
>   	struct xgbe_prv_data *pdata = netdev_priv(netdev);
>   	struct xgbe_hw_if *hw_if = &pdata->hw_if;
>   	unsigned int rx_frames, rx_riwt, rx_usecs;
> -	unsigned int tx_frames;
> +	unsigned int tx_frames, tx_usecs;
>   
>   	rx_riwt = hw_if->usec_to_riwt(pdata, ec->rx_coalesce_usecs);
>   	rx_usecs = ec->rx_coalesce_usecs;
> @@ -485,9 +486,22 @@ static int xgbe_set_coalesce(struct net_device *netdev,
>   		return -EINVAL;
>   	}
>   
> +	tx_usecs = ec->tx_coalesce_usecs;
>   	tx_frames = ec->tx_max_coalesced_frames;
>   
> +	/* Check if both tx_usecs and tx_frames are set to 0 simultaneously */
> +	if (!tx_usecs && !tx_frames) {
> +		netdev_err(netdev,
> +			   "tx_usecs and tx_frames must not be 0 together\n");
> +		return -EINVAL;
> +	}
> +
>   	/* Check the bounds of values for Tx */
> +	if (tx_usecs > XGMAC_MAX_COAL_TX_TICK) {
> +		netdev_err(netdev, "tx-usecs is limited to %d usec\n",
> +			   XGMAC_MAX_COAL_TX_TICK);
> +		return -EINVAL;
> +	}

ethtool uses netlink interface now and coalesce callbacks have extack
parameters to return error information back to user-space. It would be
great to switch to use it instead of adding more netdev_err messages.

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