netdev - Re: [net-next PATCH V2] octeontx2-pf: Add support for adaptive interrupt coalescing

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Date:   Mon, 16 May 2022 11:28:17 -0700
From:   Jakub Kicinski <kuba@...nel.org>
To:     Suman Ghosh <sumang@...vell.com>
Cc:     <davem@...emloft.net>, <edumazet@...gle.com>, <pabeni@...hat.com>,
        <sgoutham@...vell.com>, <sbhatta@...vell.com>,
        <gakula@...vell.com>, <Sunil.Goutham@...ium.com>,
        <hkelam@...vell.com>, <colin.king@...el.com>,
        <netdev@...r.kernel.org>
Subject: Re: [net-next PATCH V2] octeontx2-pf: Add support for adaptive
 interrupt coalescing

On Mon, 16 May 2022 16:23:59 +0530 Suman Ghosh wrote:
> @@ -1230,7 +1262,7 @@ static int otx2_set_link_ksettings(struct net_device *netdev,
>  
>  static const struct ethtool_ops otx2_ethtool_ops = {
>  	.supported_coalesce_params = ETHTOOL_COALESCE_USECS |
> -				     ETHTOOL_COALESCE_MAX_FRAMES,
> +				     ETHTOOL_COALESCE_MAX_FRAMES | ETHTOOL_COALESCE_USE_ADAPTIVE,

Ah there it is. Now you actually tested it with upstream :/

Please wrap the line.

Also please reject user trying to set asymmetric adaptive mode since
you don't seem to support it:

> +	/* Check and update coalesce status */
> +	if ((pfvf->flags & OTX2_FLAG_ADPTV_INT_COAL_ENABLED) ==
> +			OTX2_FLAG_ADPTV_INT_COAL_ENABLED) {
> +		priv_coalesce_status = 1;
> +		if (!ec->use_adaptive_rx_coalesce || !ec->use_adaptive_tx_coalesce)
> +			pfvf->flags &= ~OTX2_FLAG_ADPTV_INT_COAL_ENABLED;
> +	} else {
> +		priv_coalesce_status = 0;
> +		if (ec->use_adaptive_rx_coalesce || ec->use_adaptive_tx_coalesce)
> +			pfvf->flags |= OTX2_FLAG_ADPTV_INT_COAL_ENABLED;

If I'm reading this right user doing:

ethtool -C eth0 adaptive-rx on adaptive-tx off

multiple times will keep switching between adaptive and non-adaptive
mode. This will be super confusing to automation which may assume
configuration commands are idempotent.