[PATCH 1/3] net: designware: Disable DMA on removal

[Jonas Karlman]

Hi Simon,

On 2025-04-06 00:12, Simon Glass wrote:
> At present, removing the device frees struct dw_eth_dev but does not
> disable DMA. When DMA is active, packets can be received even if the
> driver is not active.
> 
> While it is possible that the memory used by the struct may remain
> untouched after removal, any other allocation may reuse that memory
> and result in DMA writing to random addresses.
> 
> In most case U-Boot does this removal in announce_and_cleanup()
> immediately before jumping to the OS. No further allocations are done
> after that point.
> 
> But with EFI_LOADER this function is not called before jumping to the
> EFI app. U-Boot continues to run while GRUB starts and finishes, as well
> as while Linux is starting up. During this time, devices cannot be
> removed, as they are in use. U-Boot completes the removal when
> efi_exit_boot_services() is called. It seems that this function does
> more allocations after calling dm_remove_devices_active() although I
> can't figure out where.
> 
> Fix this by disabling DMA when the driver is removed.
> 
> Signed-off-by: Simon Glass <sjg at chromium.org>
> Reported-by: Christian Kohlschütter <christian at kohlschutter.com>
> ---
> 
>  drivers/net/designware.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/net/designware.c b/drivers/net/designware.c
> index 07b0f49ef58..eebf14bd51a 100644
> --- a/drivers/net/designware.c
> +++ b/drivers/net/designware.c
> @@ -809,6 +809,7 @@ static int designware_eth_remove(struct udevice *dev)
>  {
>  	struct dw_eth_dev *priv = dev_get_priv(dev);
>  
> +	_dw_eth_halt(priv);

This should not really be needed, eth-uclass already call the stop() ops
that in turn call _dw_eth_halt() from the eth-uclass pre_remove() ops.

So ethernet should already have halted when remove() is called, calling
it here will probably only hide any real issue.

Regards,
Jonas

>  	free(priv->phydev);
>  	mdio_unregister(priv->bus);
>  	mdio_free(priv->bus);