Re: [PATCH net 2/2] amd-xgbe: add PCI power management for S0i3 support

[Simon Horman <horms@kernel.org>]

On Wed, Feb 25, 2026 at 04:30:01PM +0530, Raju Rangoju wrote:
> Add proper PCI power management operations to support modern standby
> (S0i3) on AMD platforms. The existing suspend/resume implementation
> did not properly handle PCI device state transitions, which prevented
> the system from reaching the deepest sleep states.
> 
> The amd_pmc driver was reporting "Last suspend didn't reach deepest
> state" when the XGBE driver was enabled.
> 
> The implementation follows the standard PCI PM model:
> 
> Suspend path:
> - Powerdown the network interface
> - Set PHY to low-power mode
> - Disable bus mastering to prevent DMA activity
> - Save PCI configuration state
> - Disable the PCI device
> - Disable wake from D3 (required for S0i3 - no Wake-on-LAN needed)
> - Set device to D3hot power state
> 
> Resume path:
> - Restore PCI power state to D0
> - Restore PCI configuration state
> - Enable the PCI device
> - Re-enable bus mastering
> - Re-enable device interrupts
> - Clear PHY low-power mode
> - Power up the network interface
> 
> Signed-off-by: Raju Rangoju <Raju.Rangoju@amd.com>
> ---
>  drivers/net/ethernet/amd/xgbe/xgbe-pci.c | 39 ++++++++++++++++++++++++
>  1 file changed, 39 insertions(+)
> 
> diff --git a/drivers/net/ethernet/amd/xgbe/xgbe-pci.c b/drivers/net/ethernet/amd/xgbe/xgbe-pci.c
> index 112d7697174c..8e392cccd065 100644
> --- a/drivers/net/ethernet/amd/xgbe/xgbe-pci.c
> +++ b/drivers/net/ethernet/amd/xgbe/xgbe-pci.c
> @@ -356,15 +356,34 @@ static int xgbe_pci_suspend(struct device *dev)
>  {
>  	struct xgbe_prv_data *pdata = dev_get_drvdata(dev);
>  	struct net_device *netdev = pdata->netdev;
> +	struct pci_dev *pdev = to_pci_dev(dev);
>  	int ret = 0;
>  
> +	if (!netdev)
> +		return 0;
> +

Can netdev be NULL here?
Same question for the check in xgbe_pci_resume().

>  	if (netif_running(netdev))
>  		ret = xgbe_powerdown(netdev);
>  
> +	/* Disable all device interrupts to prevent spurious wakeups */
> +	XP_IOWRITE(pdata, XP_INT_EN, 0x0);
> +
> +	/* Set PHY to low-power mode */
>  	pdata->lpm_ctrl = XMDIO_READ(pdata, MDIO_MMD_PCS, MDIO_CTRL1);
>  	pdata->lpm_ctrl |= MDIO_CTRL1_LPOWER;
>  	XMDIO_WRITE(pdata, MDIO_MMD_PCS, MDIO_CTRL1, pdata->lpm_ctrl);
>  
> +	/* Disable bus mastering to prevent DMA activity */
> +	pci_clear_master(pdev);
> +
> +	/* Save PCI configuration state and disable device */
> +	pci_save_state(pdev);
> +	pci_disable_device(pdev);
> +
> +	/* Disable wake from D3 - required for S0i3 deep sleep */
> +	pci_wake_from_d3(pdev, false);
> +	pci_set_power_state(pdev, PCI_D3hot);
> +
>  	return ret;
>  }
>  
> @@ -372,13 +391,33 @@ static int xgbe_pci_resume(struct device *dev)
>  {
>  	struct xgbe_prv_data *pdata = dev_get_drvdata(dev);
>  	struct net_device *netdev = pdata->netdev;
> +	struct pci_dev *pdev = to_pci_dev(dev);
>  	int ret = 0;
>  
> +	/* Restore PCI power state */
> +	pci_set_power_state(pdev, PCI_D0);
> +
> +	/* Restore PCI configuration state */
> +	pci_restore_state(pdev);
> +
> +	/* Enable PCI device */
> +	ret = pci_enable_device(pdev);
> +	if (ret)
> +		return ret;
> +
> +	/* Re-enable bus mastering */
> +	pci_set_master(pdev);
> +
> +	/* Re-enable all device interrupts */
>  	XP_IOWRITE(pdata, XP_INT_EN, 0x1fffff);
>  
> +	/* Clear PHY low-power mode */
>  	pdata->lpm_ctrl &= ~MDIO_CTRL1_LPOWER;
>  	XMDIO_WRITE(pdata, MDIO_MMD_PCS, MDIO_CTRL1, pdata->lpm_ctrl);
>  
> +	if (!netdev)
> +		return 0;
> +
>  	if (netif_running(netdev)) {
>  		ret = xgbe_powerup(netdev);
>  
> -- 
> 2.34.1
> 
>