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

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Message-ID: <199ae595-5097-4ec6-bbff-86a3e2260b23@tuxon.dev>
Date:   Thu, 23 Nov 2023 19:15:54 +0200
From:   claudiu beznea <claudiu.beznea@...on.dev>
To:     Sergey Shtylyov <s.shtylyov@....ru>, 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 23.11.2023 18:37, Sergey Shtylyov wrote:
> 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()

Yes, I kept it because of the for loop and the update of the *quota.

As commit specifies the code has been moved in IP specific RX function
keeping the initial functionality.

> 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