Subject: [PATCH net] net: cpsw: avoid alignment faults by taking NET_IP_ALIGN into account

From: Ard Biesheuvel <[email-masked]>
Date: Tue, 18 Jan 2022 11:22:04 +0100

Both versions of the CPSW driver declare a CPSW_HEADROOM_NA macro that
takes NET_IP_ALIGN into account, but fail to use it appropriately when
storing incoming packets in memory. This results in the IPv4 source and
destination addresses to appear misaligned in memory, which causes
aligment faults that need to be fixed up in software.

So let's switch from CPSW_HEADROOM to CPSW_HEADROOM_NA where needed.
This gets rid of any alignment faults on the RX path on a Beaglebone
White.

Cc: Grygorii Strashko <[email-masked]>
Cc: Ilias Apalodimas <[email-masked]>
Signed-off-by: Ard Biesheuvel <[email-masked]>
---
 drivers/net/ethernet/ti/cpsw.c      | 6 +++---
 drivers/net/ethernet/ti/cpsw_new.c  | 6 +++---
 drivers/net/ethernet/ti/cpsw_priv.c | 2 +-
 3 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/drivers/net/ethernet/ti/cpsw.c b/drivers/net/ethernet/ti/cpsw.c
index 33142d505fc8..03575c017500 100644
--- a/drivers/net/ethernet/ti/cpsw.c
+++ b/drivers/net/ethernet/ti/cpsw.c
@@ -349,7 +349,7 @@ static void cpsw_rx_handler(void *token, int len, int status)
 	struct cpsw_common	*cpsw = ndev_to_cpsw(xmeta->ndev);
 	int			pkt_size = cpsw->rx_packet_max;
 	int			ret = 0, port, ch = xmeta->ch;
-	int			headroom = CPSW_HEADROOM;
+	int			headroom = CPSW_HEADROOM_NA;
 	struct net_device	*ndev = xmeta->ndev;
 	struct cpsw_priv	*priv;
 	struct page_pool	*pool;
@@ -392,7 +392,7 @@ static void cpsw_rx_handler(void *token, int len, int status)
 	}
 
 	if (priv->xdp_prog) {
-		int headroom = CPSW_HEADROOM, size = len;
+		int size = len;
 
 		xdp_init_buff(&xdp, PAGE_SIZE, &priv->xdp_rxq[ch]);
 		if (status & CPDMA_RX_VLAN_ENCAP) {
@@ -442,7 +442,7 @@ static void cpsw_rx_handler(void *token, int len, int status)
 	xmeta->ndev = ndev;
 	xmeta->ch = ch;
 
-	dma = page_pool_get_dma_addr(new_page) + CPSW_HEADROOM;
+	dma = page_pool_get_dma_addr(new_page) + CPSW_HEADROOM_NA;
 	ret = cpdma_chan_submit_mapped(cpsw->rxv[ch].ch, new_page, dma,
 				       pkt_size, 0);
 	if (ret < 0) {
diff --git a/drivers/net/ethernet/ti/cpsw_new.c b/drivers/net/ethernet/ti/cpsw_new.c
index 279e261e4720..bd4b1528cf99 100644
--- a/drivers/net/ethernet/ti/cpsw_new.c
+++ b/drivers/net/ethernet/ti/cpsw_new.c
@@ -283,7 +283,7 @@ static void cpsw_rx_handler(void *token, int len, int status)
 {
 	struct page *new_page, *page = token;
 	void *pa = page_address(page);
-	int headroom = CPSW_HEADROOM;
+	int headroom = CPSW_HEADROOM_NA;
 	struct cpsw_meta_xdp *xmeta;
 	struct cpsw_common *cpsw;
 	struct net_device *ndev;
@@ -336,7 +336,7 @@ static void cpsw_rx_handler(void *token, int len, int status)
 	}
 
 	if (priv->xdp_prog) {
-		int headroom = CPSW_HEADROOM, size = len;
+		int size = len;
 
 		xdp_init_buff(&xdp, PAGE_SIZE, &priv->xdp_rxq[ch]);
 		if (status & CPDMA_RX_VLAN_ENCAP) {
@@ -386,7 +386,7 @@ static void cpsw_rx_handler(void *token, int len, int status)
 	xmeta->ndev = ndev;
 	xmeta->ch = ch;
 
-	dma = page_pool_get_dma_addr(new_page) + CPSW_HEADROOM;
+	dma = page_pool_get_dma_addr(new_page) + CPSW_HEADROOM_NA;
 	ret = cpdma_chan_submit_mapped(cpsw->rxv[ch].ch, new_page, dma,
 				       pkt_size, 0);
 	if (ret < 0) {
diff --git a/drivers/net/ethernet/ti/cpsw_priv.c b/drivers/net/ethernet/ti/cpsw_priv.c
index 3537502e5e8b..ba220593e6db 100644
--- a/drivers/net/ethernet/ti/cpsw_priv.c
+++ b/drivers/net/ethernet/ti/cpsw_priv.c
@@ -1122,7 +1122,7 @@ int cpsw_fill_rx_channels(struct cpsw_priv *priv)
 			xmeta->ndev = priv->ndev;
 			xmeta->ch = ch;
 
-			dma = page_pool_get_dma_addr(page) + CPSW_HEADROOM;
+			dma = page_pool_get_dma_addr(page) + CPSW_HEADROOM_NA;
 			ret = cpdma_chan_idle_submit_mapped(cpsw->rxv[ch].ch,
 							    page, dma,
 							    cpsw->rx_packet_max,
-- 
2.30.2