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

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Date: Thu, 23 Nov 2023 19:54:43 +0300
From: Sergey Shtylyov <s.shtylyov@....ru>
To: Biju Das <biju.das.jz@...renesas.com>, 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

On 11/23/23 7:48 PM, Biju Das 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.

   I fail to understand why you had (GBEth-specific) pre-conditions here to call
ravb_rx()... and involving gPTP only further confused things...

> Cheers,
> Biju

[...]

MBR, Sergey