Date:   Mon, 20 Feb 2023 02:09:31 +0100
From:   Andrew Lunn <andrew@lunn.ch>
To:     Richard Weinberger <richard@nod.at>
Cc:     netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
        pabeni@redhat.com, kuba@kernel.org, edumazet@google.com,
        davem@davemloft.net, linux-imx@nxp.com, xiaoning.wang@nxp.com,
        shenwei.wang@nxp.com, wei.fang@nxp.com
Subject: Re: [PATCH] [RFC] net: fec: Allow turning off IRQ coalescing
Message-ID: <Y/LIS3xd1iZRyVGe@lunn.ch>
References: <20230218214037.16977-1-richard@nod.at>
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In-Reply-To: <20230218214037.16977-1-richard@nod.at>
Precedence: bulk

>  /* Set threshold for interrupt coalescing */
> -static void fec_enet_itr_coal_set(struct net_device *ndev)
> +static int fec_enet_itr_coal_set(struct net_device *ndev)
>  {
> +	bool disable_rx_itr = false, disable_tx_itr = false;
>  	struct fec_enet_private *fep = netdev_priv(ndev);
> -	int rx_itr, tx_itr;
> +	struct device *dev = &fep->pdev->dev;
> +	int rx_itr = 0, tx_itr = 0;
>  
> -	/* Must be greater than zero to avoid unpredictable behavior */
> -	if (!fep->rx_time_itr || !fep->rx_pkts_itr ||
> -	    !fep->tx_time_itr || !fep->tx_pkts_itr)
> -		return;
> +	if (!fep->rx_time_itr || !fep->rx_pkts_itr) {
> +		if (fep->rx_time_itr || fep->rx_pkts_itr) {
> +			dev_warn(dev, "Rx coalesced frames and usec have to be "
> +				      "both positive or both zero to disable Rx "
> +				      "coalescence completely\n");
> +			return -EINVAL;
> +		}

Hi Richard

Why do this validation here, and not in fec_enet_set_coalesce() where
there are already checks? fec_enet_set_coalesce() also has extack, so
you can return useful messages to user space, not just the kernel log.

    Andrew