netdev - Re: [PATCH net-next v2 11/21] net: ravb: Move DBAT configuration to the driver's ndo

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Date: Wed, 20 Dec 2023 13:41:18 +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 11/21] net: ravb: Move DBAT configuration to
 the driver's ndo_open API



On 19.12.2023 20:54, Sergey Shtylyov wrote:
> On 12/17/23 3:54 PM, claudiu beznea wrote:
> 
> [...]
> 
>>>>> From: Claudiu Beznea <claudiu.beznea.uj@...renesas.com>
>>>>>
>>>>> DBAT setup was done in the driver's probe API. As some IP variants switch
>>>>> to reset mode (and thus registers' content is lost) when setting clocks
>>>>> (due to module standby functionality) to be able to implement runtime PM
>>>>> move the DBAT configuration in the driver's ndo_open API.
>>>>>
>>>>> This commit prepares the code for the addition of runtime PM.
>>>>>
>>>>> Signed-off-by: Claudiu Beznea <claudiu.beznea.uj@...renesas.com>
>>>>
>>>> Reviewed-by: Sergey Shtylyov <s.shtylyov@....ru>
>>>>
>>>> [...]
>>>>> diff --git a/drivers/net/ethernet/renesas/ravb_main.c b/drivers/net/ethernet/renesas/ravb_main.c
>>>>> index 04eaa1967651..6b8ca08be35e 100644
>>>>> --- a/drivers/net/ethernet/renesas/ravb_main.c
>>>>> +++ b/drivers/net/ethernet/renesas/ravb_main.c
>>>>> @@ -1822,6 +1822,7 @@ static int ravb_open(struct net_device *ndev)
>>>>>  		napi_enable(&priv->napi[RAVB_NC]);
>>>>>  
>>>>>  	ravb_set_delay_mode(ndev);
>>>>> +	ravb_write(ndev, priv->desc_bat_dma, DBAT);
>>>
>>>    Looking at it again, I suspect this belong in ravb_dmac_init()...
>>
>> ravb_dmac_init() is called from multiple places in this driver, e.g.,
> 
>    It's purpose is to configure AVB-DMAC and DBAT is the AVB-DMAC register,
> right?

It is. But it is pointless to configure it more than one time after
ravb_open() has been called as the register content is not changed until IP
enters reset mode (though ravb_close() now).

> 
>> ravb_set_ringparam(), ravb_tx_timeout_work().
> 
>    I know. Its value is only calculated once, in ravb_probe(), right?

right

> 
>> I'm afraid we may broke the behavior of these if DBAT setup is moved

I was wrong here. DBAT is not changed by IP while TX/RX is working.

> 
>    Do not be afraid! :-)
> 
>> in ravb_dmac_init(). This is also
>> valid for setting delay (see patch 10/12).
> 
>    I don't think there will be a problem either... but maybe we
> should call it in ravb_emac_init() indeed.
> 
> [...]
> 
> MBR, Sergey