netdev - Re: [PATCH net-next v2 4/5] net: ravb: Do not apply RX checksum settings to hardware if the interface is down

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Message-ID: <CADT+UeAfCTd8c+dHn3mgT=g6Boip=oRPdkODMN_j2KaROcT0AQ@mail.gmail.com>
Date: Sun, 11 Feb 2024 08:56:20 +0000
From: Biju Das <biju.das.au@...il.com>
To: Sergey Shtylyov <s.shtylyov@....ru>
Cc: Biju Das <biju.das.jz@...renesas.com>, 
	Claudiu Beznea <claudiu.beznea.uj@...renesas.com>, claudiu.beznea@...on.dev, 
	"David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, 
	Jakub Kicinski <kuba@...nel.org>, linux-kernel@...r.kernel.org, 
	linux-renesas-soc@...r.kernel.org, netdev@...r.kernel.org, 
	Paolo Abeni <pabeni@...hat.com>
Subject: Re: [PATCH net-next v2 4/5] net: ravb: Do not apply RX checksum
 settings to hardware if the interface is down

>>> From: Claudiu Beznea <claudiu.beznea.uj@...renesas.com>
>>>
>>> Do not apply the RX checksum 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 the clocks will
>>> switch the IP to reset mode, which will lead to losing register
>>> contents) and applying settings in reset mode is not an option.
>>> Instead, cache the RX checksum settings and apply them in ravb_open()
>>> through ravb_emac_init().
>>> This has been solved by introducing pm_runtime_active() check. The
>>> device runtime PM usage counter has been incremented to avoid
>>> disabling the device clocks while the check is in progress (if any).
>>>
>>> Commit prepares for the addition of runtime PM.
>>>
>>> Signed-off-by: Claudiu Beznea <claudiu.beznea.uj@...renesas.com>
>>
>> Reviewed-by: Sergey Shtylyov <s.shtylyov@....ru>
>
> This will do the same job, without code duplication right?
>
>> static int ravb_set_features(struct net_device *ndev,
>>     netdev_features_t features)
>> {
>> struct ravb_private *priv = netdev_priv(ndev);
>> struct device *dev = &priv->pdev->dev;
>> const struct ravb_hw_info *info = priv->info;
>>
>> pm_runtime_get_noresume(dev);
>> if (!pm_runtime_active(dev)) {
>> pm_runtime_put_noidle(dev);
>> ndev->features = features;
>> return 0;
>> }
>>
>> return info->set_feature(ndev, features);

> We now leak the device reference by not calling pm_runtime_put_noidle()
>after this statement...

Oops. So this leak  can be fixed like [1]

>  The approach seems sane though -- Claudiu, please consider following it.

[1]
static int ravb_set_features(struct net_device *ndev,
    netdev_features_t features)
{
struct ravb_private *priv = netdev_priv(ndev);
const struct ravb_hw_info *info = priv->info;
struct device *dev = &priv->pdev->dev;
bool pm_active;

pm_runtime_get_noresume(dev);
pm_active = pm_runtime_active(dev);
pm_runtime_put_noidle(dev);
if (pm_active )
     return info->set_feature(ndev, features);

ndev->features = features;
return 0;
}