netdev - Re: [PATCH net-next v2 10/21] net: ravb: Move delay mode set in the driver's ndo

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Date: Wed, 20 Dec 2023 14:02:57 +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,
 richardcochran@...il.com, p.zabel@...gutronix.de,
 yoshihiro.shimoda.uh@...esas.com, wsa+renesas@...g-engineering.com,
 geert+renesas@...der.be
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 net-next v2 10/21] net: ravb: Move delay mode set in the
 driver's ndo_open API



On 19.12.2023 20:40, Sergey Shtylyov wrote:
> On 12/17/23 3:49 PM, claudiu beznea wrote:
> 
> [...]
>>>> From: Claudiu Beznea <claudiu.beznea.uj@...renesas.com>
>>>>
>>>> Delay parse and set were done in the driver's probe API. As some IP
>>>
>>>    Parsing and setting?
>>>
>>>> variants switch to reset mode (and thus registers' content is lost) when
>>>
>>>    Register.
>>>
>>>> setting clocks (due to module standby functionality) to be able to
>>>> implement runtime PM keep the delay parsing in the driver's probe function
>>>> and move the delay apply function to the driver's ndo_open API.
>>>
>>>    Applying?
>>>
>>>> Signed-off-by: Claudiu Beznea <claudiu.beznea.uj@...renesas.com>
>>> [...]
>>>
>>>> diff --git a/drivers/net/ethernet/renesas/ravb_main.c b/drivers/net/ethernet/renesas/ravb_main.c
>>>> index 5e01e03e1b43..04eaa1967651 100644
>>>> --- a/drivers/net/ethernet/renesas/ravb_main.c
>>>> +++ b/drivers/net/ethernet/renesas/ravb_main.c
>>> [...]
>>>> @@ -1806,6 +1821,8 @@ static int ravb_open(struct net_device *ndev)
>>>>  	if (info->nc_queues)
>>>>  		napi_enable(&priv->napi[RAVB_NC]);
>>>>  
>>>> +	ravb_set_delay_mode(ndev);
>>>> +
>>>
>>>    I suspect this belongs in ravb_dmac_init() now...
>>
>> I'm confused... Why? To me this seems more like MAC-PHY interface related.
> 
>    APSR's full name is AVB-DMAC product specific register. :-)

As ravb_dmac_init() is called in multiple places I don't think it worth
configuring delays more than once in ravb_open().

Moreover TX/RX delay is something specific to the MAC-PHY interface (and
could be influenced also by the wiring length b/w MAC and PHY).

Just because it is in the DMAC address space I don't think it worth having
it in ravb_dmac_init() (for the above mentioned reasons).

> 
>> Though I'm not sure what ravb_dmac_init() purpose is.
> 
>    To configure and start the AVB-DMAC, apparently. :-)
> 
> [...]
> 
> MRB, Sergey