linux-kernel - Re: [PATCH net-next v2] net: macb: Add shutdown operation support

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Message-ID: <129a670d-14b5-4f9e-b01b-0a88a0017741@gmail.com>
Date: Sat, 7 Jun 2025 18:24:53 +0200
From: Heiner Kallweit <hkallweit1@...il.com>
To: Claudiu Beznea <claudiu.beznea@...on.dev>,
 Abin Joseph <abin.joseph@....com>, nicolas.ferre@...rochip.com,
 andrew+netdev@...n.ch, davem@...emloft.net, edumazet@...gle.com,
 kuba@...nel.org, pabeni@...hat.com
Cc: git@....com, netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next v2] net: macb: Add shutdown operation support

On 07.06.2025 14:28, Claudiu Beznea wrote:
> Hi, Abin,
> 
> On 07.06.2025 10:57, Abin Joseph wrote:
>> Implement the shutdown hook to ensure clean and complete deactivation of
>> MACB controller. The shutdown sequence is protected with 'rtnl_lock()'
>> to serialize access and prevent race conditions while detaching and
>> closing the network device. This ensure a safe transition when the Kexec
>> utility calls the shutdown hook, facilitating seamless loading and
>> booting of a new kernel from the currently running one.
>>
>> Signed-off-by: Abin Joseph <abin.joseph@....com>
>> ---
>>
>> Changes in v2:
>> Update the commit description
>> Update the code to call the close only when admin is up
>>
>> ---
>>  drivers/net/ethernet/cadence/macb_main.c | 14 ++++++++++++++
>>  1 file changed, 14 insertions(+)
>>
>> diff --git a/drivers/net/ethernet/cadence/macb_main.c b/drivers/net/ethernet/cadence/macb_main.c
>> index e1e8bd2ec155..5bb08f518d54 100644
>> --- a/drivers/net/ethernet/cadence/macb_main.c
>> +++ b/drivers/net/ethernet/cadence/macb_main.c
>> @@ -5650,6 +5650,19 @@ static int __maybe_unused macb_runtime_resume(struct device *dev)
>>  	return 0;
>>  }
>>  
>> +static void macb_shutdown(struct platform_device *pdev)
>> +{
>> +	struct net_device *netdev = platform_get_drvdata(pdev);
>> +
>> +	rtnl_lock();
>> +	netif_device_detach(netdev);
>> +
>> +	if (netif_running(netdev))
>> +		dev_close(netdev);
> 
> Apart from closing the interface should we also invoke the remove?
> 
As part of closing the interface dev_close() sends notifiers.
I don't think that's something we want during shutdown.
Typically the shutdown() callback just has to quiesce the device.

> Consider the new loaded kernel will not use this interface and some
> hardware resources may remain on while not used by the newly loaded kernel.
> 
> E.g., there is this code in macb_remove():
> 
> 		if (!pm_runtime_suspended(&pdev->dev)) {
> 			macb_clks_disable(bp->pclk, bp->hclk, bp->tx_clk,
> 					  bp->rx_clk, bp->tsu_clk);
> 			pm_runtime_set_suspended(&pdev->dev);
> 		}
> 
> 
> Thank you,
> Claudiu
> 
>> +
>> +	rtnl_unlock();
>> +}
>> +
>>  static const struct dev_pm_ops macb_pm_ops = {
>>  	SET_SYSTEM_SLEEP_PM_OPS(macb_suspend, macb_resume)
>>  	SET_RUNTIME_PM_OPS(macb_runtime_suspend, macb_runtime_resume, NULL)
>> @@ -5663,6 +5676,7 @@ static struct platform_driver macb_driver = {
>>  		.of_match_table	= of_match_ptr(macb_dt_ids),
>>  		.pm	= &macb_pm_ops,
>>  	},
>> +	.shutdown	= macb_shutdown,
>>  };
>>  
>>  module_platform_driver(macb_driver);
> 
>