netdev - RE: [PATCH 06/13] net: ravb: Let IP specific receive function to interrogate descriptors

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Message-ID:
 <TYVPR01MB112791203FFACF4484A9EAC4E86B9A@TYVPR01MB11279.jpnprd01.prod.outlook.com>
Date: Thu, 23 Nov 2023 16:48:32 +0000
From: Biju Das <biju.das.jz@...renesas.com>
To: Sergey Shtylyov <s.shtylyov@....ru>, Claudiu.Beznea
	<claudiu.beznea@...on.dev>, "davem@...emloft.net" <davem@...emloft.net>,
	"edumazet@...gle.com" <edumazet@...gle.com>, "kuba@...nel.org"
	<kuba@...nel.org>, "pabeni@...hat.com" <pabeni@...hat.com>,
	"p.zabel@...gutronix.de" <p.zabel@...gutronix.de>, Yoshihiro Shimoda
	<yoshihiro.shimoda.uh@...esas.com>, "geert+renesas@...der.be"
	<geert+renesas@...der.be>, "wsa+renesas@...g-engineering.com"
	<wsa+renesas@...g-engineering.com>, Prabhakar Mahadev Lad
	<prabhakar.mahadev-lad.rj@...renesas.com>,
	"sergei.shtylyov@...entembedded.com" <sergei.shtylyov@...entembedded.com>,
	Mitsuhiro Kimura <mitsuhiro.kimura.kc@...esas.com>, Masaru Nagai
	<masaru.nagai.vx@...esas.com>
CC: "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"linux-renesas-soc@...r.kernel.org" <linux-renesas-soc@...r.kernel.org>,
	"linux-kernel@...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

Hi Sergey Shtylyov,

> 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)?

It was initial version of the driver. Now Claudiu optimized.

Cheers,
Biju

>
> > +   if (ravb_rx(ndev, &quota, q))
> > +           goto out;
>
>    This restores the behavior before:
>
> https://git.kern/
> el.org%2Fpub%2Fscm%2Flinux%2Fkernel%2Fgit%2Ftorvalds%2Flinux.git%2Fcommit%
> 2F%3Fid%3D3d4e37df882b0f4f28b7223a42492650b71252c5&data=05%7C01%7Cbiju.das
> .jz%40bp.renesas.com%7C3c7d64ca68104738fb3f08dbec427e84%7C53d82571da1947e4
> 9cb4625a166a4a2a%7C0%7C0%7C638363542555838396%7CUnknown%7CTWFpbGZsb3d8eyJW
> IjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7
> C%7C&sdata=lGBD8FdwY26OygYAV4Sd8bzIIO4rS7rNiYabQKaQAtA%3D&reserved=0
>
>    So does look correct. :-)
>
> MBR, Sergey