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

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Message-ID: <509add4e-5dff-4f30-b96b-488919fedb77@linux.dev>
Date: Sat, 19 Jul 2025 16:16:49 +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: [RESEND PATCH net-next] amd-xgbe: Configure and retrieve
 'tx-usecs' for Tx coalescing

On 19.07.2025 08:26, 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;
> +	}
>   	if (tx_frames > pdata->tx_desc_count) {
>   		netdev_err(netdev, "tx-frames is limited to %d frames\n",
>   			   pdata->tx_desc_count);
> @@ -499,6 +513,7 @@ static int xgbe_set_coalesce(struct net_device *netdev,
>   	pdata->rx_frames = rx_frames;
>   	hw_if->config_rx_coalesce(pdata);
>   
> +	pdata->tx_usecs = tx_usecs;
>   	pdata->tx_frames = tx_frames;
>   	hw_if->config_tx_coalesce(pdata);
>

I'm not quite sure, but it looks like it never works. config_tx_coalesce()
callback equals to xgbe_config_tx_coalesce() which is implemented as:

static int xgbe_config_tx_coalesce(struct xgbe_prv_data *pdata)
{
         return 0;
}

How is it expected to change anything from HW side?

> @@ -830,7 +845,7 @@ static int xgbe_set_channels(struct net_device *netdev,
>   }
>   
>   static const struct ethtool_ops xgbe_ethtool_ops = {
> -	.supported_coalesce_params = ETHTOOL_COALESCE_RX_USECS |
> +	.supported_coalesce_params = ETHTOOL_COALESCE_USECS |
>   				     ETHTOOL_COALESCE_MAX_FRAMES,
>   	.get_drvinfo = xgbe_get_drvinfo,
>   	.get_msglevel = xgbe_get_msglevel,
> diff --git a/drivers/net/ethernet/amd/xgbe/xgbe.h b/drivers/net/ethernet/amd/xgbe/xgbe.h
> index 42fa4f84ff01..e330ae9ea685 100755
> --- a/drivers/net/ethernet/amd/xgbe/xgbe.h
> +++ b/drivers/net/ethernet/amd/xgbe/xgbe.h
> @@ -272,6 +272,7 @@
>   /* Default coalescing parameters */
>   #define XGMAC_INIT_DMA_TX_USECS		1000
>   #define XGMAC_INIT_DMA_TX_FRAMES	25
> +#define XGMAC_MAX_COAL_TX_TICK		100000
>   
>   #define XGMAC_MAX_DMA_RIWT		0xff
>   #define XGMAC_INIT_DMA_RX_USECS		30