netdev - Re: [PATCH net-next v2 13/21] net: ravb: Set config mode in ndo_open and reset mode in ndo

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Message-ID: <ba18b668-94c0-4cab-9d2c-87ac6c3f8f8e@tuxon.dev>
Date: Sun, 17 Dec 2023 15:15:02 +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 13/21] net: ravb: Set config mode in ndo_open
 and reset mode in ndo_close



On 16.12.2023 19:28, Sergey Shtylyov wrote:
> On 12/14/23 2:45 PM, Claudiu wrote:
> 
>> From: Claudiu Beznea <claudiu.beznea.uj@...renesas.com>
>>
>> As some IP variants switch to reset mode (and thus registers' content is
> 
>    Register.
> 
>> lost) when setting clocks (due to module standby functionality) to be able
>> to implement runtime PM and save more power, set the IP's operation mode to
> 
>    Operating.
> 
>> reset at the end of the probe. Along with it, in the ndo_open API the IP
>> will be switched to configuration, then operational mode. In the ndo_close
>> API, the IP will be switched back to reset mode. This allows implementing
>> runtime PM and, along with it, save more power when the IP is not used.
>>
>> 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 db9222fc57c2..31a1f8a83652 100644
>> --- a/drivers/net/ethernet/renesas/ravb_main.c
>> +++ b/drivers/net/ethernet/renesas/ravb_main.c
> [...]
>> @@ -1821,13 +1845,19 @@ static int ravb_open(struct net_device *ndev)
>>  	if (info->nc_queues)
>>  		napi_enable(&priv->napi[RAVB_NC]);
>>  
>> +	/* Set AVB config mode */
>> +	error = ravb_set_config_mode(ndev);
>> +	if (error)
>> +		goto out_napi_off;
>> +
> 
>    I suspect this too belongs in ravb_dmac_init() now...

What I can do here is to keep PTP/GAC specific settings from
ravb_set_config_mode() in a separate function close to PTP setup and remove
ravb_set_config_mode() at all as ravb_dmac_init() switches anyway the IP to
config mode. But with this I don't know how the PTP/GAC will be influenced
as I don't have a setup to check it. From my memories, the commit that
introduces the setup of PTP when switching to config mode did this by
intention, so I'm not sure weather playing around with this is the way to
go forward. Do you remember something specific about this?

> 
> [...]
>> @@ -2875,19 +2886,30 @@ static int ravb_probe(struct platform_device *pdev)
>>  
>>  	device_set_wakeup_capable(&pdev->dev, 1);
>>  
>> +	/* Reset MAC as the module will be runtime disabled at this moment.
>> +	 * This saves power. MAC will be switched back to configuration mode
>> +	 * in ravb_open().
>> +	 */
>> +	error = ravb_set_reset_mode(ndev);
>> +	if (error)
>> +		goto out_netdev_unregister;
>> +
> 
>    I think this now races with the register_netdev() call above (the device
> can be opened before it returns)! Should be called before register_netdev()...
> 

Good point! Thanks!

> [...]
> 
> MBR, Sergey