qualcommax: qca_edma: add ethtool DMA reset

The EDMA block has a reset line of its own, but the driver asserts it
only at probe and when it rebuilds the rings. qca_edma is built in and
the switch sits on the conduit, so a reboot is the only other way back
to the engine's power-on state. Implement the ethtool reset op for
ETH_RESET_DMA with the rebuild ring resizing already uses.

Assisted-by: Claude:claude-opus-5-5
Signed-off-by: Julius Bairaktaris <julius@bairaktaris.de>
Link: https://github.com/openwrt/openwrt/pull/25700
Signed-off-by: Robert Marko <robimarko@gmail.com>

target/linux/qualcommax/files/drivers/net/ethernet/qualcomm/qca_edma.c

@@ -1422,6 +1422,23 @@ static int edma_set_ringparam(struct net_device *netdev,
 				ring->tx_pending, ring->rx_pending);
 }
 
+/* The rebuild asserts the block's reset line, so it is the DMA reset too. */
+static int edma_reset(struct net_device *netdev, u32 *flags)
+{
+	struct edma_priv *priv = netdev_priv(netdev);
+	int ret;
+
+	if (!(*flags & ETH_RESET_DMA))
+		return -EINVAL;
+
+	ret = edma_reconfigure(priv, priv->rx_page_order, priv->num_queues,
+			       priv->tx_ring_size, priv->rx_ring_size);
+	if (!ret)
+		*flags &= ~ETH_RESET_DMA;
+
+	return ret;
+}
+
 /* A ring interrupts once it holds more frames than its threshold, and its
  * timer interrupts for fewer once they have waited that long. A threshold of
  * zero interrupts on every frame, which leaves the timer nothing to do.
@@ -1725,6 +1742,7 @@ static const struct ethtool_ops edma_ethtool_ops = {
 	.get_rxfh_indir_size = edma_get_rxfh_indir_size,
 	.get_rxfh = edma_get_rxfh,
 	.set_rxfh = edma_set_rxfh,
+	.reset = edma_reset,
 };
 
 static void edma_rx_vlan_strip(struct edma_priv *priv,