[PATCH net-next v2 4/4] net: stmmac: add Rx HWTS metadata to XDP ZC receive pkt

[Song Yoong Siang <yoong.siang.song@xxxxxxxxx>]

Add receive hardware timestamp metadata support via kfunc to XDP Zero Copy
receive packets.

Signed-off-by: Song Yoong Siang <yoong.siang.song@xxxxxxxxx>
---
 .../net/ethernet/stmicro/stmmac/stmmac_main.c | 29 +++++++++++++++++--
 1 file changed, 26 insertions(+), 3 deletions(-)

diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
index 7f1c0c36de8c..bcaafeea118b 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
@@ -1611,6 +1611,12 @@ static int stmmac_alloc_rx_buffers_zc(struct stmmac_priv *priv,
 	struct stmmac_rx_queue *rx_q = &dma_conf->rx_queue[queue];
 	int i;
 
+	/* struct stmmac_xdp_buff is using cb field (maximum size of 24 bytes)
+	 * in struct xdp_buff_xsk to stash driver specific information. Thus,
+	 * use this macro to make sure no size violations.
+	 */
+	XSK_CHECK_PRIV_TYPE(struct stmmac_xdp_buff);
+
 	for (i = 0; i < dma_conf->dma_rx_size; i++) {
 		struct stmmac_rx_buffer *buf;
 		dma_addr_t dma_addr;
@@ -4903,7 +4909,7 @@ static struct sk_buff *stmmac_construct_skb_zc(struct stmmac_channel *ch,
 
 static void stmmac_dispatch_skb_zc(struct stmmac_priv *priv, u32 queue,
 				   struct dma_desc *p, struct dma_desc *np,
-				   struct xdp_buff *xdp)
+				   struct xdp_buff *xdp, ktime_t rx_hwts)
 {
 	struct stmmac_channel *ch = &priv->channel[queue];
 	struct skb_shared_hwtstamps *shhwtstamp = NULL;
@@ -4921,7 +4927,7 @@ static void stmmac_dispatch_skb_zc(struct stmmac_priv *priv, u32 queue,
 
 	shhwtstamp = skb_hwtstamps(skb);
 	memset(shhwtstamp, 0, sizeof(struct skb_shared_hwtstamps));
-	stmmac_get_rx_hwtstamp(priv, p, np, &shhwtstamp->hwtstamp);
+	shhwtstamp->hwtstamp = rx_hwts;
 
 	stmmac_rx_vlan(priv->dev, skb);
 	skb->protocol = eth_type_trans(skb, priv->dev);
@@ -4999,6 +5005,16 @@ static bool stmmac_rx_refill_zc(struct stmmac_priv *priv, u32 queue, u32 budget)
 	return ret;
 }
 
+static struct stmmac_xdp_buff *xsk_buff_to_stmmac_ctx(struct xdp_buff *xdp)
+{
+	/* In XDP zero copy data path, xdp field in struct xdp_buff_xsk is used
+	 * to represent incoming packet, whereas cb field in the same structure
+	 * is used to store driver specific info. Thus, struct stmmac_xdp_buff
+	 * is laid on top of xdp and cb fields of struct xdp_buff_xsk.
+	 */
+	return (struct stmmac_xdp_buff *)xdp;
+}
+
 static int stmmac_rx_zc(struct stmmac_priv *priv, int limit, u32 queue)
 {
 	struct stmmac_rx_queue *rx_q = &priv->dma_conf.rx_queue[queue];
@@ -5028,8 +5044,10 @@ static int stmmac_rx_zc(struct stmmac_priv *priv, int limit, u32 queue)
 	}
 	while (count < limit) {
 		struct stmmac_rx_buffer *buf;
+		struct stmmac_xdp_buff *ctx;
 		unsigned int buf1_len = 0;
 		struct dma_desc *np, *p;
+		ktime_t rx_hwts = 0;
 		int entry;
 		int res;
 
@@ -5113,6 +5131,10 @@ static int stmmac_rx_zc(struct stmmac_priv *priv, int limit, u32 queue)
 			goto read_again;
 		}
 
+		stmmac_get_rx_hwtstamp(priv, p, np, &rx_hwts);
+		ctx = xsk_buff_to_stmmac_ctx(buf->xdp);
+		ctx->rx_hwts = rx_hwts;
+
 		/* XDP ZC Frame only support primary buffers for now */
 		buf1_len = stmmac_rx_buf1_len(priv, p, status, len);
 		len += buf1_len;
@@ -5132,7 +5154,8 @@ static int stmmac_rx_zc(struct stmmac_priv *priv, int limit, u32 queue)
 
 		switch (res) {
 		case STMMAC_XDP_PASS:
-			stmmac_dispatch_skb_zc(priv, queue, p, np, buf->xdp);
+			stmmac_dispatch_skb_zc(priv, queue, p, np, buf->xdp,
+					       rx_hwts);
 			xsk_buff_free(buf->xdp);
 			break;
 		case STMMAC_XDP_CONSUMED:
-- 
2.34.1