[net PATCH 13/13] fbnic: Disable PTP completions during the Tx force-flush

From: Alexander Duyck <alexanderduyck@fb.com>

When the Tx queues fail to go idle, fbnic_wait_all_queues_idle() falls
back to fbnic_tx_flush(), which sets FBNIC_TMI_DROP_CTRL_EN. That bit
only drops packets at the Tx MAC Interface start of packet protection FIFO.

The PTP completion path is governed by a separate bit in the same
register. With only the drop enable set, a timestamped frame has its
packet discarded while the matching completion is still forwarded to
the host. fbnic_clean_tsq() then walks the ring with no packet left to
match it against and reports "Tx timestamp without matching packet".
The drop does not retire the completion either, as the completion FIFO
is only drained when the completion disable is set.

Set FBNIC_TMI_DROP_CTRL_CMPL_DIS together with the drop enable so the
completions are drained rather than leaked to the host, and clear both
bits again when the flush is turned off.

Fixes: 40bf06a160a1 ("eth: fbnic: Implement Tx queue alloc/start/stop/free")
Signed-off-by: Alexander Duyck <alexanderduyck@fb.com>
---
 drivers/net/ethernet/meta/fbnic/fbnic_csr.h  |    1 +
 drivers/net/ethernet/meta/fbnic/fbnic_txrx.c |   10 +++++++---
 2 files changed, 8 insertions(+), 3 deletions(-)

diff --git a/drivers/net/ethernet/meta/fbnic/fbnic_csr.h b/drivers/net/ethernet/meta/fbnic/fbnic_csr.h
index d7583243e5cd..c371ac9f78c1 100644
--- a/drivers/net/ethernet/meta/fbnic/fbnic_csr.h
+++ b/drivers/net/ethernet/meta/fbnic/fbnic_csr.h

@@ -441,6 +441,7 @@ enum {
 #define FBNIC_TMI_SOP_PROT_CTRL		0x04400		/* 0x11000 */
 #define FBNIC_TMI_DROP_CTRL		0x04401		/* 0x11004 */
 #define FBNIC_TMI_DROP_CTRL_EN			CSR_BIT(0)
+#define FBNIC_TMI_DROP_CTRL_CMPL_DIS		CSR_BIT(1)
 #define FBNIC_TMI_DROP_PKTS		0x04402		/* 0x11008 */
 #define FBNIC_TMI_DROP_BYTE_L		0x04403		/* 0x1100c */
 #define FBNIC_TMI_ILLEGAL_PTP_REQS	0x04409		/* 0x11024 */

diff --git a/drivers/net/ethernet/meta/fbnic/fbnic_txrx.c b/drivers/net/ethernet/meta/fbnic/fbnic_txrx.c
index c572a0062e77..9bc934c6771d 100644
--- a/drivers/net/ethernet/meta/fbnic/fbnic_txrx.c
+++ b/drivers/net/ethernet/meta/fbnic/fbnic_txrx.c

@@ -2349,15 +2349,19 @@ void fbnic_disable(struct fbnic_net *fbn)
 
 static void fbnic_tx_flush(struct fbnic_dev *fbd)
 {
+	u32 drop_ctrl = FBNIC_TMI_DROP_CTRL_EN | FBNIC_TMI_DROP_CTRL_CMPL_DIS;
+
 	netdev_warn(fbd->netdev, "triggering Tx flush\n");
 
-	fbnic_rmw32(fbd, FBNIC_TMI_DROP_CTRL, FBNIC_TMI_DROP_CTRL_EN,
-		    FBNIC_TMI_DROP_CTRL_EN);
+	/* Drop packets and retire their PTP completions */
+	fbnic_rmw32(fbd, FBNIC_TMI_DROP_CTRL, drop_ctrl, drop_ctrl);
 }
 
 static void fbnic_tx_flush_off(struct fbnic_dev *fbd)
 {
-	fbnic_rmw32(fbd, FBNIC_TMI_DROP_CTRL, FBNIC_TMI_DROP_CTRL_EN, 0);
+	u32 drop_ctrl = FBNIC_TMI_DROP_CTRL_EN | FBNIC_TMI_DROP_CTRL_CMPL_DIS;
+
+	fbnic_rmw32(fbd, FBNIC_TMI_DROP_CTRL, drop_ctrl, 0);
 }
 
 struct fbnic_idle_regs {