net: stmmac: Add launch time support to XDP ZC

Enable launch time (Time-Based Scheduling) support for XDP zero copy via
the XDP Tx metadata framework.

This patch has been tested with tools/testing/selftests/bpf/xdp_hw_metadata
on Intel Tiger Lake platform. Below are the test steps and result.

Test 1: Send a single packet with the launch time set to 1 s in the future.

Test steps:
1. On the DUT, start the xdp_hw_metadata selftest application:
   $ sudo ./xdp_hw_metadata enp0s30f4 -l 1000000000 -L 1

2. On the Link Partner, send a UDP packet with VLAN priority 1 to port 9091
   of the DUT.

Result:
When the launch time is set to 1 s in the future, the delta between the
launch time and the transmit hardware timestamp is 16.963 us, as shown in
printout of the xdp_hw_metadata application below.
  0x55b5864717a8: rx_desc[4]->addr=88100 addr=88100 comp_addr=88100 EoP
  No rx_hash, err=-95
  HW RX-time:   1734579065767717328 (sec:1734579065.7677)
                delta to User RX-time sec:0.0004 (375.624 usec)
  XDP RX-time:   1734579065768004454 (sec:1734579065.7680)
                 delta to User RX-time sec:0.0001 (88.498 usec)
  No rx_vlan_tci or rx_vlan_proto, err=-95
  0x55b5864717a8: ping-pong with csum=5619 (want 0000)
                  csum_start=34 csum_offset=6
  HW RX-time:   1734579065767717328 (sec:1734579065.7677)
                delta to HW Launch-time sec:1.0000 (1000000.000 usec)
  0x55b5864717a8: complete tx idx=4 addr=4018
  HW Launch-time:   1734579066767717328 (sec:1734579066.7677)
                    delta to HW TX-complete-time sec:0.0000 (16.963 usec)
  HW TX-complete-time:   1734579066767734291 (sec:1734579066.7677)
                         delta to User TX-complete-time sec:0.0001
                         (130.408 usec)
  XDP RX-time:   1734579065768004454 (sec:1734579065.7680)
                 delta to User TX-complete-time sec:0.9999
                (999860.245 usec)
  HW RX-time:   1734579065767717328 (sec:1734579065.7677)
                delta to HW TX-complete-time sec:1.0000 (1000016.963 usec)
  0x55b5864717a8: complete rx idx=132 addr=88100

Test 2: Send 1000 packets with a 10 ms interval and the launch time set to
        500 us in the future.

Test steps:
1. On the DUT, start the xdp_hw_metadata selftest application:
   $ sudo chrt -f 99 ./xdp_hw_metadata enp0s30f4 -l 500000 -L 1 > \
     /dev/shm/result.log

2. On the Link Partner, send 1000 UDP packets with a 10 ms interval and
   VLAN priority 1 to port 9091 of the DUT.

Result:
When the launch time is set to 500 us in the future, the average delta
between the launch time and the transmit hardware timestamp is 13.854 us,
as shown in the analysis of /dev/shm/result.log below. The XDP launch time
works correctly in sending 1000 packets continuously.
  Min delta: 08.410 us
  Avr delta: 13.854 us
  Max delta: 17.076 us
  Total packets forwarded: 1000

Signed-off-by: Song Yoong Siang <yoong.siang.song@intel.com>
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
Reviewed-by: Choong Yong Liang <yong.liang.choong@linux.intel.com>
Link: https://patch.msgid.link/20250216093430.957880-4-yoong.siang.song@intel.com

drivers/net/ethernet/stmicro/stmmac/stmmac.h

@@ -106,6 +106,8 @@ struct stmmac_metadata_request {
 	struct stmmac_priv *priv;
 	struct dma_desc *tx_desc;
 	bool *set_ic;
+	struct dma_edesc *edesc;
+	int tbs;
 };
 
 struct stmmac_xsk_tx_complete {

drivers/net/ethernet/stmicro/stmmac/stmmac_main.c

@@ -2491,9 +2491,20 @@ static u64 stmmac_xsk_fill_timestamp(void *_priv)
 	return 0;
 }
 
+static void stmmac_xsk_request_launch_time(u64 launch_time, void *_priv)
+{
+	struct timespec64 ts = ns_to_timespec64(launch_time);
+	struct stmmac_metadata_request *meta_req = _priv;
+
+	if (meta_req->tbs & STMMAC_TBS_EN)
+		stmmac_set_desc_tbs(meta_req->priv, meta_req->edesc, ts.tv_sec,
+				    ts.tv_nsec);
+}
+
 static const struct xsk_tx_metadata_ops stmmac_xsk_tx_metadata_ops = {
 	.tmo_request_timestamp		= stmmac_xsk_request_timestamp,
 	.tmo_fill_timestamp		= stmmac_xsk_fill_timestamp,
+	.tmo_request_launch_time	= stmmac_xsk_request_launch_time,
 };
 
 static bool stmmac_xdp_xmit_zc(struct stmmac_priv *priv, u32 queue, u32 budget)
@@ -2577,6 +2588,8 @@ static bool stmmac_xdp_xmit_zc(struct stmmac_priv *priv, u32 queue, u32 budget)
 		meta_req.priv = priv;
 		meta_req.tx_desc = tx_desc;
 		meta_req.set_ic = &set_ic;
+		meta_req.tbs = tx_q->tbs;
+		meta_req.edesc = &tx_q->dma_entx[entry];
 		xsk_tx_metadata_request(meta, &stmmac_xsk_tx_metadata_ops,
 					&meta_req);
 		if (set_ic) {