Re: [PATCH net-next 3/3] net: usb: smsc95xx: suspend PHY during USB suspend

[Oliver Neukum <oneukum@suse.com>]

On 30.03.26 15:42, Parthiban Veerasooran wrote:
> The smsc95xx driver registers a PHY device but does not currently
> propagate suspend events to it when the USB interface is suspended.
> 
> Call phy_suspend() from the driver's suspend callback so the attached
> PHY can properly enter low-power state during system or runtime
> suspend. This aligns smsc95xx suspend handling with other network
> drivers that manage an external or integrated PHY.
> 
> Without this, the PHY may remain active and fail to execute its own
> suspend procedure, leading to unnecessary power consumption or
> incorrect resume behavior.
> 
> This change is also required for the EVB-LAN8670-USB Rev.D0 device to
> support OATC10-compliant sleep and wake functionality.
> 
> Signed-off-by: Parthiban Veerasooran <parthiban.veerasooran@microchip.com>
> ---
>   drivers/net/usb/smsc95xx.c | 6 ++++++
>   1 file changed, 6 insertions(+)
> 
> diff --git a/drivers/net/usb/smsc95xx.c b/drivers/net/usb/smsc95xx.c
> index 42e4048b574b..3a6e03b7410a 100644
> --- a/drivers/net/usb/smsc95xx.c
> +++ b/drivers/net/usb/smsc95xx.c
> @@ -1550,6 +1550,12 @@ static int smsc95xx_suspend(struct usb_interface *intf, pm_message_t message)
>   
>   	pdata->pm_task = current;
>   
> +	if (pdata->phydev) {
> +		ret = phy_suspend(pdata->phydev);
> +		if (ret)
> +			return ret;
> +	}

At this point you have suspended the phy.
Hence the device can no longer transmit

> +
>   	ret = usbnet_suspend(intf, message);

This wants to

1. drain the queue if you do runtime PM
2. can return -EBUSY

>   	if (ret < 0) {
>   		netdev_warn(dev->net, "usbnet_suspend error\n");

And here it will return in the error case. With the phy
already suspended.

And, as a question of principle: Why do you suspend the phy
in suspend(), but take no action in resume()?

	Regards
		Oliver