linux-kernel - Re: [net-next RFC v3 2/7] net: ravb: Align poll function with NAPI docs

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Date: Mon, 15 Apr 2024 13:44:19 +0200
From: Niklas Söderlund <niklas.soderlund+renesas@...natech.se>
To: Paul Barker <paul.barker.ct@...renesas.com>
Cc: Sergey Shtylyov <s.shtylyov@....ru>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Geert Uytterhoeven <geert+renesas@...der.be>,
	netdev@...r.kernel.org, linux-renesas-soc@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [net-next RFC v3 2/7] net: ravb: Align poll function with NAPI
 docs

Hi Paul,

Thanks for your work.

On 2024-04-15 10:47:59 +0100, Paul Barker wrote:
> Call napi_complete_done() in accordance with the documentation in
> `Documentation/networking/napi.rst`.

The way I understand it napi_complete() is still OK to use, it's just a 
wrapper for napi_complete_done(napi, 0). But of course using 
napi_complete_done() is better if you want to use the busypolling status 
returned. Maybe the commit message can be updated to reflect this 
change, how about?

    net: ravb: Consider busypolling status when re-enabling interrupts

    Make use of the busypolling status returned from NAPI complete to decide 
    if interrupts shall be re-enabled or not. This is useful to reduce the 
    interrupt overhead.

    While at it switch to using napi_complete_done() as it take into account 
    the work done when providing the busypolling status.

> 
> Signed-off-by: Paul Barker <paul.barker.ct@...renesas.com>
> ---
>  drivers/net/ethernet/renesas/ravb_main.c | 26 ++++++++++--------------
>  1 file changed, 11 insertions(+), 15 deletions(-)
> 
> diff --git a/drivers/net/ethernet/renesas/ravb_main.c b/drivers/net/ethernet/renesas/ravb_main.c
> index 33f8043143c1..1ac599a044b2 100644
> --- a/drivers/net/ethernet/renesas/ravb_main.c
> +++ b/drivers/net/ethernet/renesas/ravb_main.c
> @@ -1340,23 +1340,19 @@ static int ravb_poll(struct napi_struct *napi, int budget)
>  	if (priv->rx_fifo_errors != ndev->stats.rx_fifo_errors)
>  		ndev->stats.rx_fifo_errors = priv->rx_fifo_errors;
>  
> -	if (work_done == budget)
> -		goto out;
> -
> -	napi_complete(napi);
> -
> -	/* Re-enable RX/TX interrupts */
> -	spin_lock_irqsave(&priv->lock, flags);
> -	if (!info->irq_en_dis) {
> -		ravb_modify(ndev, RIC0, mask, mask);
> -		ravb_modify(ndev, TIC,  mask, mask);
> -	} else {
> -		ravb_write(ndev, mask, RIE0);
> -		ravb_write(ndev, mask, TIE);
> +	if (work_done < budget && napi_complete_done(napi, work_done)) {
> +		/* Re-enable RX/TX interrupts */
> +		spin_lock_irqsave(&priv->lock, flags);
> +		if (!info->irq_en_dis) {
> +			ravb_modify(ndev, RIC0, mask, mask);
> +			ravb_modify(ndev, TIC,  mask, mask);
> +		} else {
> +			ravb_write(ndev, mask, RIE0);
> +			ravb_write(ndev, mask, TIE);
> +		}
> +		spin_unlock_irqrestore(&priv->lock, flags);
>  	}
> -	spin_unlock_irqrestore(&priv->lock, flags);
>  
> -out:
>  	return work_done;
>  }
>  
> -- 
> 2.39.2
> 

-- 
Kind Regards,
Niklas Söderlund