linux-kernel - Re: [PATCH 06/13] net: ravb: Let IP specific receive function to interrogate descriptors

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Message-ID: <b626455a-f7a4-2684-725c-c679dd75a515@omp.ru>
Date:   Thu, 23 Nov 2023 19:37:27 +0300
From:   Sergey Shtylyov <s.shtylyov@....ru>
To:     Claudiu <claudiu.beznea@...on.dev>, <davem@...emloft.net>,
        <edumazet@...gle.com>, <kuba@...nel.org>, <pabeni@...hat.com>,
        <p.zabel@...gutronix.de>, <yoshihiro.shimoda.uh@...esas.com>,
        <geert+renesas@...der.be>, <wsa+renesas@...g-engineering.com>,
        <biju.das.jz@...renesas.com>,
        <prabhakar.mahadev-lad.rj@...renesas.com>,
        <sergei.shtylyov@...entembedded.com>,
        <mitsuhiro.kimura.kc@...esas.com>, <masaru.nagai.vx@...esas.com>
CC:     <netdev@...r.kernel.org>, <linux-renesas-soc@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>,
        Claudiu Beznea <claudiu.beznea.uj@...renesas.com>
Subject: Re: [PATCH 06/13] net: ravb: Let IP specific receive function to
 interrogate descriptors

On 11/20/23 11:45 AM, Claudiu wrote:

> From: Claudiu Beznea <claudiu.beznea.uj@...renesas.com>
> 
> ravb_poll() initial code used to interrogate the first descriptor of the
> RX queue in case gptp is false to know if ravb_rx() should be called.
> This is done for non GPTP IPs. For GPTP IPs the driver PTP specific

   It's called gPTP, AFAIK.

> information was used to know if receive function should be called. As
> every IP has it's own receive function that interrogates the RX descriptor

   Its own.

> list in the same way the ravb_poll() was doing there is no need to double
> check this in ravb_poll(). Removing the code form ravb_poll() and

   From ravb_poll().

> adjusting ravb_rx_gbeth() leads to a cleaner code.
> 
> Signed-off-by: Claudiu Beznea <claudiu.beznea.uj@...renesas.com>
> ---
>  drivers/net/ethernet/renesas/ravb_main.c | 18 ++++++------------
>  1 file changed, 6 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/net/ethernet/renesas/ravb_main.c b/drivers/net/ethernet/renesas/ravb_main.c
> index 588e3be692d3..0fc9810c5e78 100644
> --- a/drivers/net/ethernet/renesas/ravb_main.c
> +++ b/drivers/net/ethernet/renesas/ravb_main.c
> @@ -771,12 +771,15 @@ static bool ravb_rx_gbeth(struct net_device *ndev, int *quota, int q)
>  	int limit;
>  
>  	entry = priv->cur_rx[q] % priv->num_rx_ring[q];
> +	desc = &priv->gbeth_rx_ring[entry];
> +	if (desc->die_dt == DT_FEMPTY)
> +		return false;
> +

   I don't understand what this buys us, the following *while* loop will
be skipped anyway, and the *for* loop as well, I think... And ravb_rx_rcar()
doesn't have that anyway...

> @@ -1279,25 +1282,16 @@ static int ravb_poll(struct napi_struct *napi, int budget)
>  	struct net_device *ndev = napi->dev;
>  	struct ravb_private *priv = netdev_priv(ndev);
>  	const struct ravb_hw_info *info = priv->info;
> -	bool gptp = info->gptp || info->ccc_gac;
> -	struct ravb_rx_desc *desc;
>  	unsigned long flags;
>  	int q = napi - priv->napi;
>  	int mask = BIT(q);
>  	int quota = budget;
> -	unsigned int entry;
>  
> -	if (!gptp) {
> -		entry = priv->cur_rx[q] % priv->num_rx_ring[q];
> -		desc = &priv->gbeth_rx_ring[entry];
> -	}
>  	/* Processing RX Descriptor Ring */
>  	/* Clear RX interrupt */
>  	ravb_write(ndev, ~(mask | RIS0_RESERVED), RIS0);
> -	if (gptp || desc->die_dt != DT_FEMPTY) {
> -		if (ravb_rx(ndev, &quota, q))
> -			goto out;
> -	}

  I don't really understand this code (despite I've AKCed it)...
Biju, could you explain this (well, you tried already but I don't
buy it anymore)?

> +	if (ravb_rx(ndev, &quota, q))
> +		goto out;

   This restores the behavior before:

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=3d4e37df882b0f4f28b7223a42492650b71252c5

   So does look correct. :-)

MBR, Sergey