linux-kernel - 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: <78688143-e777-c98b-01eb-813f0fe67491@omp.ru>
Date: Sat, 16 Dec 2023 20:28:20 +0300
From: Sergey Shtylyov <s.shtylyov@....ru>
To: Claudiu <claudiu.beznea@...on.dev>, <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 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...

[...]
> @@ -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()...

[...]

MBR, Sergey