ethernet: ionic: Fix DMA mapping tests

Change error values of `ionic_tx_map_single()` and `ionic_tx_map_frag()`
from 0 to `DMA_MAPPING_ERROR` to prevent collision with 0 as a valid
address.

This also fixes the use of `dma_mapping_error()` to test against 0 in
`ionic_xdp_post_frame()`

Fixes: 0f3154e ("ionic: Add Tx and Rx handling")
Fixes: 56e41ee ("ionic: better dma-map error handling")
Fixes: ac8813c ("ionic: convert Rx queue buffers to use page_pool")
Signed-off-by: Thomas Fourier <fourier.thomas@gmail.com>
Reviewed-by: Brett Creeley <brett.creeley@amd.com>
Link: https://patch.msgid.link/20250619094538.283723-2-fourier.thomas@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: Thomas-fourier

drivers/net/ethernet/pensando/ionic/ionic_txrx.c

@@ -321,7 +321,7 @@ static int ionic_xdp_post_frame(struct ionic_queue *q, struct xdp_frame *frame,
 					   len, DMA_TO_DEVICE);
 	} else /* XDP_REDIRECT */ {
 		dma_addr = ionic_tx_map_single(q, frame->data, len);
-		if (!dma_addr)
+		if (dma_addr == DMA_MAPPING_ERROR)
 			return -EIO;
 	}
 
@@ -357,7 +357,7 @@ static int ionic_xdp_post_frame(struct ionic_queue *q, struct xdp_frame *frame,
 			} else {
 				dma_addr = ionic_tx_map_frag(q, frag, 0,
 							     skb_frag_size(frag));
-				if (dma_mapping_error(q->dev, dma_addr)) {
+				if (dma_addr == DMA_MAPPING_ERROR) {
 					ionic_tx_desc_unmap_bufs(q, desc_info);
 					return -EIO;
 				}
@@ -1083,7 +1083,7 @@ static dma_addr_t ionic_tx_map_single(struct ionic_queue *q,
 		net_warn_ratelimited("%s: DMA single map failed on %s!\n",
 				     dev_name(dev), q->name);
 		q_to_tx_stats(q)->dma_map_err++;
-		return 0;
+		return DMA_MAPPING_ERROR;
 	}
 	return dma_addr;
 }
@@ -1100,7 +1100,7 @@ static dma_addr_t ionic_tx_map_frag(struct ionic_queue *q,
 		net_warn_ratelimited("%s: DMA frag map failed on %s!\n",
 				     dev_name(dev), q->name);
 		q_to_tx_stats(q)->dma_map_err++;
-		return 0;
+		return DMA_MAPPING_ERROR;
 	}
 	return dma_addr;
 }
@@ -1116,7 +1116,7 @@ static int ionic_tx_map_skb(struct ionic_queue *q, struct sk_buff *skb,
 	int frag_idx;
 
 	dma_addr = ionic_tx_map_single(q, skb->data, skb_headlen(skb));
-	if (!dma_addr)
+	if (dma_addr == DMA_MAPPING_ERROR)
 		return -EIO;
 	buf_info->dma_addr = dma_addr;
 	buf_info->len = skb_headlen(skb);
@@ -1126,7 +1126,7 @@ static int ionic_tx_map_skb(struct ionic_queue *q, struct sk_buff *skb,
 	nfrags = skb_shinfo(skb)->nr_frags;
 	for (frag_idx = 0; frag_idx < nfrags; frag_idx++, frag++) {
 		dma_addr = ionic_tx_map_frag(q, frag, 0, skb_frag_size(frag));
-		if (!dma_addr)
+		if (dma_addr == DMA_MAPPING_ERROR)
 			goto dma_fail;
 		buf_info->dma_addr = dma_addr;
 		buf_info->len = skb_frag_size(frag);