netdev - Re: [PATCH net-next v2 13/14] ravb: Update EMAC configuration mode comment

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Date:   Sun, 10 Oct 2021 20:24:04 +0300
From:   Sergey Shtylyov <s.shtylyov@....ru>
To:     Biju Das <biju.das.jz@...renesas.com>,
        Sergei Shtylyov <sergei.shtylyov@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        "Jakub Kicinski" <kuba@...nel.org>
CC:     Geert Uytterhoeven <geert+renesas@...der.be>,
        Sergey Shtylyov <s.shtylyov@...russia.ru>,
        Adam Ford <aford173@...il.com>, Andrew Lunn <andrew@...n.ch>,
        Yuusuke Ashizuka <ashiduka@...itsu.com>,
        Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-renesas-soc@...r.kernel.org" 
        <linux-renesas-soc@...r.kernel.org>,
        Chris Paterson <Chris.Paterson2@...esas.com>,
        Biju Das <biju.das@...renesas.com>,
        "Prabhakar Mahadev Lad" <prabhakar.mahadev-lad.rj@...renesas.com>
Subject: Re: [PATCH net-next v2 13/14] ravb: Update EMAC configuration mode
 comment

On 10/10/21 1:56 PM, Biju Das wrote:

[...]
>>>>> Update EMAC configuration mode comment from "PAUSE prohibition"
>>>>> to "EMAC Mode: PAUSE prohibition; Duplex; TX; RX; CRC Pass Through;
>>>>> Promiscuous".
>>>>>
>>>>> Signed-off-by: Biju Das <biju.das.jz@...renesas.com>
>>>>> Suggested-by: Sergey Shtylyov <s.shtylyov@....ru>
>>>>> ---
>>>>> v1->v2:
>>>>>    * No change
>>>>> V1:
>>>>>    * New patch.
>>>>> ---
>>>>>    drivers/net/ethernet/renesas/ravb_main.c | 2 +-
>>>>>    1 file changed, 1 insertion(+), 1 deletion(-)
>>>>>
>>>>> diff --git a/drivers/net/ethernet/renesas/ravb_main.c
>>>>> b/drivers/net/ethernet/renesas/ravb_main.c
>>>>> index 9a770a05c017..b78aca235c37 100644
>>>>> --- a/drivers/net/ethernet/renesas/ravb_main.c
>>>>> +++ b/drivers/net/ethernet/renesas/ravb_main.c
>>>>> @@ -519,7 +519,7 @@ static void ravb_emac_init_gbeth(struct
>>>>> net_device
>>>> *ndev)
>>>>>    	/* Receive frame limit set register */
>>>>>    	ravb_write(ndev, GBETH_RX_BUFF_MAX + ETH_FCS_LEN, RFLR);
>>>>>
>>>>> -	/* PAUSE prohibition */
>>>>> +	/* EMAC Mode: PAUSE prohibition; Duplex; TX; RX; CRC Pass Through;
>>>>> +Promiscuous */
>>>>
>>>>      Promiscuous mode, really? Why?!
>>>
>>> This is TOE related,
> 
> I meant the context here is TOE register related. That is what I meant.
> 
>>
>>     The promiscuous mode is supported by _all_ Ethernet controllers, I
>> think.
>>
>>> and is recommendation from BSP team.
>>
>>     On what grounds?
> 
> The reference implementation has this on. Any way it is good catch. 
> I will turn it off and check.
> 
> by looking at the RJ LED's there is not much activity and packet statistics also show not much activity by default.
> 
> How can we check, it is overloading the controller? So that I can compare with and without this setting

   Maybe it doesn't get overloaded that simply, but definitely the promiscuous mode is not the thing
for the normal driver use...

>>> If you think it is wrong.
>>> I can take this out. Please let me know. Currently the board is booting
>> and everything works without issues.
>>
>>     Please do take it out. It'll needlessly overload the controller when
>> there's much traffic on the local network.
> 
> 
> I can see much activity only on RJ45 LED's when I call tcpdump or by setting IP link set eth0 promisc on.
> Otherwise there is no traffic at all.

   Sounds like the kernel initially sets the RX mode with IFF_PROMISC = 0 and thus clear ECMR.PRM but I don't
see where it does this? Could you instrument ravb_set_tx_mode() plz?

> Regards,
> Biju

[...]

MBR, Sergey