From: Satish Kharat <satishkh@cisco.com>

The admin receive queue needs pre-posted DMA buffers for incoming
mailbox messages from VFs. Each buffer is a kmalloc'd region mapped
for DMA (2048 bytes, sufficient for any MBOX message).

Add enic_admin_rq_fill() to post buffers at open time, and
enic_admin_rq_drain() to unmap and free them at close time.
Wire both into the admin channel open/close paths.

Signed-off-by: Satish Kharat <satishkh@cisco.com>
---
 drivers/net/ethernet/cisco/enic/enic_admin.c | 66 +++++++++++++++++++++++++++-
 1 file changed, 64 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/cisco/enic/enic_admin.c b/drivers/net/ethernet/cisco/enic/enic_admin.c
index d1abe6a50095..a8fcd5f116d1 100644
--- a/drivers/net/ethernet/cisco/enic/enic_admin.c
+++ b/drivers/net/ethernet/cisco/enic/enic_admin.c
@@ -3,6 +3,7 @@
 
 #include <linux/kernel.h>
 #include <linux/netdevice.h>
+#include <linux/dma-mapping.h>
 
 #include "vnic_dev.h"
 #include "vnic_wq.h"
@@ -23,10 +24,63 @@ static void enic_admin_wq_buf_clean(struct vnic_wq *wq,
 {
 }
 
-/* No-op: admin RQ buffer teardown is handled in enic_admin_channel_close */
 static void enic_admin_rq_buf_clean(struct vnic_rq *rq,
 				    struct vnic_rq_buf *buf)
 {
+	struct enic *enic = vnic_dev_priv(rq->vdev);
+
+	if (!buf->os_buf)
+		return;
+
+	dma_unmap_single(&enic->pdev->dev, buf->dma_addr, buf->len,
+			 DMA_FROM_DEVICE);
+	kfree(buf->os_buf);
+	buf->os_buf = NULL;
+}
+
+static int enic_admin_rq_post_one(struct enic *enic)
+{
+	struct vnic_rq *rq = &enic->admin_rq;
+	struct rq_enet_desc *desc;
+	dma_addr_t dma_addr;
+	void *buf;
+
+	buf = kmalloc(ENIC_ADMIN_BUF_SIZE, GFP_KERNEL);
+	if (!buf)
+		return -ENOMEM;
+
+	dma_addr = dma_map_single(&enic->pdev->dev, buf, ENIC_ADMIN_BUF_SIZE,
+				  DMA_FROM_DEVICE);
+	if (dma_mapping_error(&enic->pdev->dev, dma_addr)) {
+		kfree(buf);
+		return -ENOMEM;
+	}
+
+	desc = vnic_rq_next_desc(rq);
+	rq_enet_desc_enc(desc, (u64)dma_addr | VNIC_PADDR_TARGET,
+			 RQ_ENET_TYPE_ONLY_SOP, ENIC_ADMIN_BUF_SIZE);
+	vnic_rq_post(rq, buf, 0, dma_addr, ENIC_ADMIN_BUF_SIZE, 0);
+
+	return 0;
+}
+
+static int enic_admin_rq_fill(struct enic *enic)
+{
+	struct vnic_rq *rq = &enic->admin_rq;
+	int err;
+
+	while (vnic_rq_desc_avail(rq) > 0) {
+		err = enic_admin_rq_post_one(enic);
+		if (err)
+			return err;
+	}
+
+	return 0;
+}
+
+static void enic_admin_rq_drain(struct enic *enic)
+{
+	vnic_rq_clean(&enic->admin_rq, enic_admin_rq_buf_clean);
 }
 
 static int enic_admin_qp_type_set(struct enic *enic, u32 enable)
@@ -138,6 +192,13 @@ int enic_admin_channel_open(struct enic *enic)
 	vnic_wq_enable(&enic->admin_wq);
 	vnic_rq_enable(&enic->admin_rq);
 
+	err = enic_admin_rq_fill(enic);
+	if (err) {
+		netdev_err(enic->netdev,
+			   "Failed to fill admin RQ buffers: %d\n", err);
+		goto disable_queues;
+	}
+
 	err = enic_admin_qp_type_set(enic, 1);
 	if (err) {
 		netdev_err(enic->netdev,
@@ -151,6 +212,7 @@ int enic_admin_channel_open(struct enic *enic)
 	vnic_wq_disable(&enic->admin_wq);
 	vnic_rq_disable(&enic->admin_rq);
 	enic_admin_qp_type_set(enic, 0);
+	enic_admin_rq_drain(enic);
 	enic_admin_free_resources(enic);
 	return err;
 }
@@ -166,7 +228,7 @@ void enic_admin_channel_close(struct enic *enic)
 	enic_admin_qp_type_set(enic, 0);
 
 	vnic_wq_clean(&enic->admin_wq, enic_admin_wq_buf_clean);
-	vnic_rq_clean(&enic->admin_rq, enic_admin_rq_buf_clean);
+	enic_admin_rq_drain(enic);
 	vnic_cq_clean(&enic->admin_cq[0]);
 	vnic_cq_clean(&enic->admin_cq[1]);
 	vnic_intr_clean(&enic->admin_intr);

-- 
2.43.0