linux-kernel - Re: [PATCH net-next v2 20/21] net: ravb: Do not apply RX CSUM settings to hardware if the interface is down

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Date: Sun, 17 Dec 2023 16:34:33 +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 20/21] net: ravb: Do not apply RX CSUM
 settings to hardware if the interface is down



On 16.12.2023 22:36, Sergey Shtylyov wrote:
> On 12/14/23 2:45 PM, Claudiu wrote:
> 
>> From: Claudiu Beznea <claudiu.beznea.uj@...renesas.com>
>>
>> Do not apply the RX CSUM settings to hardware if the interface is down. In
>> case runtime PM is enabled, and while the interface is down, the IP will be
>> in reset mode (as for some platforms disabling/enabling the clocks will
>> switch the IP to standby mode, which will lead to losing registers'
> 
>    To/From perhaps?
>    And just "register".
> 
>> content) and applying settings in reset mode is not an option. Instead,
>> cache the RX CSUM settings and apply them in ravb_open().
> 
>    Have this issue actually occurred for you?

Setting RX CSUM while the if is down? No.

> 
>> Commit prepares for the addition of runtime PM.
>>
>> 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 633346b6cd7c..9ff943dff522 100644
>> --- a/drivers/net/ethernet/renesas/ravb_main.c
>> +++ b/drivers/net/ethernet/renesas/ravb_main.c
>> @@ -1868,6 +1868,15 @@ static int ravb_open(struct net_device *ndev)
>>  	if (info->gptp || info->ccc_gac)
>>  		ravb_ptp_init(ndev, priv->pdev);
>>  
>> +	/* Apply features that might have been changed while the interface
>> +	 * was down.
>> +	 */
>> +	if (ndev->hw_features & NETIF_F_RXCSUM) {
> 
>    I'm afraid this is a wrong field; we need ndev->features, no?

RX CSUM is not enabled for all ravb aware devices (see struct
ravb_hw_info::net_hw_features). We should be setting the ECMR only for
these ones. ravb_hw_info::net_hw_features is set in ndev->hw_features in
probe(). So here code checks if platforms supports RXCSUM and then below it
applies what has been requested though ndo_set_features(), if any.

> 
>> +		u32 val = (ndev->features & NETIF_F_RXCSUM) ? ECMR_RCSC : 0;
>> +
>> +		ravb_modify(ndev, ECMR, ECMR_RCSC, val);
>> +	}
>> +
> 
>    The ECMR setting is already done in ravb_emac_init_rcar(), no need
> to duplicate it here, I think...

Ok, it worth being moved there.

> 
>>  	/* PHY control start */
>>  	error = ravb_phy_start(ndev);
>>  	if (error)
>> @@ -2337,6 +2346,9 @@ static void ravb_set_rx_csum(struct net_device *ndev, bool enable)
>>  	struct ravb_private *priv = netdev_priv(ndev);
>>  	unsigned long flags;
>>  
>> +	if (!netif_running(ndev))
> 
>    Racy as well...

It's also called with rtnl_mutex locked.

> 
>> +		return;
>> +
> 
>    Hm, sh_eth.c doesn't have such check -- perhaps should be fixed
> as well...
> 
> [...]
> 
> MBR, Sergey