The tieoff descriptor is a RX DMA descriptor ring of size one. It gets
configured onto queues for Wake-on-LAN during system-wide suspend when
hardware does not support disabling individual queues
(MACB_CAPS_QUEUE_DISABLE).

MACB/GEM driver allocates it alongside the main RX ring
inside macb_alloc() at open. Free is done by macb_free() at close.

Change to allocate once at probe and free on probe failure or device
removal. This makes the tieoff descriptor lifetime much longer,
avoiding repeating coherent buffer allocation on each open/close cycle.

Main benefit: we dissociate its lifetime from the main ring's lifetime.
That way there is less work to be doing on resources (re)alloc. This
currently happens on close/open, but will soon also happen on context
swap operations (set_ringparam, change_mtu, set_channels, etc).

Signed-off-by: Théo Lebrun <theo.lebrun@bootlin.com>
---
 drivers/net/ethernet/cadence/macb_main.c | 75 
+++++++++++++++++---------------
 1 file changed, 41 insertions(+), 34 deletions(-)

diff --git a/drivers/net/ethernet/cadence/macb_main.c 

b/drivers/net/ethernet/cadence/macb_main.c
index 8b52122bc134..951a7f080225 100644

--- a/drivers/net/ethernet/cadence/macb_main.c
+++ b/drivers/net/ethernet/cadence/macb_main.c

 static void macb_init_rings(struct macb *bp)

@@ -2832,8 +2801,6 @@ static void macb_init_rings(struct macb *bp)
 	bp->queues[0].tx_head = 0;
 	bp->queues[0].tx_tail = 0;
 	desc->ctrl |= MACB_BIT(TX_WRAP);
-
-	macb_init_tieoff(bp);
 }

 static void macb_reset_hw(struct macb *bp)

@@ -5518,6 +5485,38 @@ static int eyeq5_init(struct platform_device 

*pdev)
 	return ret;
 }

+static int macb_alloc_tieoff(struct macb *bp)
+{
+	/* Tieoff is a workaround in case HW cannot disable queues, for PM. 
*/
+	if (bp->caps & MACB_CAPS_QUEUE_DISABLE)
+		return 0;