Adding upstream version 6.1.76.upstream/6.1.76

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1352 insertions, 0 deletions

diff --git a/drivers/misc/bcm-vk/bcm_vk_msg.c b/drivers/misc/bcm-vk/bcm_vk_msg.c
new file mode 100644
index 000000000..3c081504f
--- /dev/null
+++ b/drivers/misc/bcm-vk/bcm_vk_msg.c
@@ -0,0 +1,1352 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright 2018-2020 Broadcom.
+ */
+
+#include <linux/delay.h>
+#include <linux/fs.h>
+#include <linux/hash.h>
+#include <linux/interrupt.h>
+#include <linux/list.h>
+#include <linux/module.h>
+#include <linux/poll.h>
+#include <linux/sizes.h>
+#include <linux/spinlock.h>
+#include <linux/timer.h>
+
+#include "bcm_vk.h"
+#include "bcm_vk_msg.h"
+#include "bcm_vk_sg.h"
+
+/* functions to manipulate the transport id in msg block */
+#define BCM_VK_MSG_Q_SHIFT	 4
+#define BCM_VK_MSG_Q_MASK	 0xF
+#define BCM_VK_MSG_ID_MASK	 0xFFF
+
+#define BCM_VK_DMA_DRAIN_MAX_MS	  2000
+
+/* number x q_size will be the max number of msg processed per loop */
+#define BCM_VK_MSG_PROC_MAX_LOOP 2
+
+/* module parameter */
+static bool hb_mon = true;
+module_param(hb_mon, bool, 0444);
+MODULE_PARM_DESC(hb_mon, "Monitoring heartbeat continuously.\n");
+static int batch_log = 1;
+module_param(batch_log, int, 0444);
+MODULE_PARM_DESC(batch_log, "Max num of logs per batch operation.\n");
+
+static bool hb_mon_is_on(void)
+{
+	return hb_mon;
+}
+
+static u32 get_q_num(const struct vk_msg_blk *msg)
+{
+	u32 q_num = msg->trans_id & BCM_VK_MSG_Q_MASK;
+
+	if (q_num >= VK_MSGQ_PER_CHAN_MAX)
+		q_num = VK_MSGQ_NUM_DEFAULT;
+	return q_num;
+}
+
+static void set_q_num(struct vk_msg_blk *msg, u32 q_num)
+{
+	u32 trans_q;
+
+	if (q_num >= VK_MSGQ_PER_CHAN_MAX)
+		trans_q = VK_MSGQ_NUM_DEFAULT;
+	else
+		trans_q = q_num;
+
+	msg->trans_id = (msg->trans_id & ~BCM_VK_MSG_Q_MASK) | trans_q;
+}
+
+static u32 get_msg_id(const struct vk_msg_blk *msg)
+{
+	return ((msg->trans_id >> BCM_VK_MSG_Q_SHIFT) & BCM_VK_MSG_ID_MASK);
+}
+
+static void set_msg_id(struct vk_msg_blk *msg, u32 val)
+{
+	msg->trans_id = (val << BCM_VK_MSG_Q_SHIFT) | get_q_num(msg);
+}
+
+static u32 msgq_inc(const struct bcm_vk_sync_qinfo *qinfo, u32 idx, u32 inc)
+{
+	return ((idx + inc) & qinfo->q_mask);
+}
+
+static
+struct vk_msg_blk __iomem *msgq_blk_addr(const struct bcm_vk_sync_qinfo *qinfo,
+					 u32 idx)
+{
+	return qinfo->q_start + (VK_MSGQ_BLK_SIZE * idx);
+}
+
+static u32 msgq_occupied(const struct bcm_vk_msgq __iomem *msgq,
+			 const struct bcm_vk_sync_qinfo *qinfo)
+{
+	u32 wr_idx, rd_idx;
+
+	wr_idx = readl_relaxed(&msgq->wr_idx);
+	rd_idx = readl_relaxed(&msgq->rd_idx);
+
+	return ((wr_idx - rd_idx) & qinfo->q_mask);
+}
+
+static
+u32 msgq_avail_space(const struct bcm_vk_msgq __iomem *msgq,
+		     const struct bcm_vk_sync_qinfo *qinfo)
+{
+	return (qinfo->q_size - msgq_occupied(msgq, qinfo) - 1);
+}
+
+/* number of retries when enqueue message fails before returning EAGAIN */
+#define BCM_VK_H2VK_ENQ_RETRY 10
+#define BCM_VK_H2VK_ENQ_RETRY_DELAY_MS 50
+
+bool bcm_vk_drv_access_ok(struct bcm_vk *vk)
+{
+	return (!!atomic_read(&vk->msgq_inited));
+}
+
+void bcm_vk_set_host_alert(struct bcm_vk *vk, u32 bit_mask)
+{
+	struct bcm_vk_alert *alert = &vk->host_alert;
+	unsigned long flags;
+
+	/* use irqsave version as this maybe called inside timer interrupt */
+	spin_lock_irqsave(&vk->host_alert_lock, flags);
+	alert->notfs |= bit_mask;
+	spin_unlock_irqrestore(&vk->host_alert_lock, flags);
+
+	if (test_and_set_bit(BCM_VK_WQ_NOTF_PEND, vk->wq_offload) == 0)
+		queue_work(vk->wq_thread, &vk->wq_work);
+}
+
+/*
+ * Heartbeat related defines
+ * The heartbeat from host is a last resort.  If stuck condition happens
+ * on the card, firmware is supposed to detect it.  Therefore, the heartbeat
+ * values used will be more relaxed on the driver, which need to be bigger
+ * than the watchdog timeout on the card.  The watchdog timeout on the card
+ * is 20s, with a jitter of 2s => 22s.  We use a value of 27s here.
+ */
+#define BCM_VK_HB_TIMER_S 3
+#define BCM_VK_HB_TIMER_VALUE (BCM_VK_HB_TIMER_S * HZ)
+#define BCM_VK_HB_LOST_MAX (27 / BCM_VK_HB_TIMER_S)
+
+static void bcm_vk_hb_poll(struct timer_list *t)
+{
+	u32 uptime_s;
+	struct bcm_vk_hb_ctrl *hb = container_of(t, struct bcm_vk_hb_ctrl,
+						 timer);
+	struct bcm_vk *vk = container_of(hb, struct bcm_vk, hb_ctrl);
+
+	if (bcm_vk_drv_access_ok(vk) && hb_mon_is_on()) {
+		/* read uptime from register and compare */
+		uptime_s = vkread32(vk, BAR_0, BAR_OS_UPTIME);
+
+		if (uptime_s == hb->last_uptime)
+			hb->lost_cnt++;
+		else /* reset to avoid accumulation */
+			hb->lost_cnt = 0;
+
+		dev_dbg(&vk->pdev->dev, "Last uptime %d current %d, lost %d\n",
+			hb->last_uptime, uptime_s, hb->lost_cnt);
+
+		/*
+		 * if the interface goes down without any activity, a value
+		 * of 0xFFFFFFFF will be continuously read, and the detection
+		 * will be happened eventually.
+		 */
+		hb->last_uptime = uptime_s;
+	} else {
+		/* reset heart beat lost cnt */
+		hb->lost_cnt = 0;
+	}
+
+	/* next, check if heartbeat exceeds limit */
+	if (hb->lost_cnt > BCM_VK_HB_LOST_MAX) {
+		dev_err(&vk->pdev->dev, "Heartbeat Misses %d times, %d s!\n",
+			BCM_VK_HB_LOST_MAX,
+			BCM_VK_HB_LOST_MAX * BCM_VK_HB_TIMER_S);
+
+		bcm_vk_blk_drv_access(vk);
+		bcm_vk_set_host_alert(vk, ERR_LOG_HOST_HB_FAIL);
+	}
+	/* re-arm timer */
+	mod_timer(&hb->timer, jiffies + BCM_VK_HB_TIMER_VALUE);
+}
+
+void bcm_vk_hb_init(struct bcm_vk *vk)
+{
+	struct bcm_vk_hb_ctrl *hb = &vk->hb_ctrl;
+
+	timer_setup(&hb->timer, bcm_vk_hb_poll, 0);
+	mod_timer(&hb->timer, jiffies + BCM_VK_HB_TIMER_VALUE);
+}
+
+void bcm_vk_hb_deinit(struct bcm_vk *vk)
+{
+	struct bcm_vk_hb_ctrl *hb = &vk->hb_ctrl;
+
+	del_timer(&hb->timer);
+}
+
+static void bcm_vk_msgid_bitmap_clear(struct bcm_vk *vk,
+				      unsigned int start,
+				      unsigned int nbits)
+{
+	spin_lock(&vk->msg_id_lock);
+	bitmap_clear(vk->bmap, start, nbits);
+	spin_unlock(&vk->msg_id_lock);
+}
+
+/*
+ * allocate a ctx per file struct
+ */
+static struct bcm_vk_ctx *bcm_vk_get_ctx(struct bcm_vk *vk, const pid_t pid)
+{
+	u32 i;
+	struct bcm_vk_ctx *ctx = NULL;
+	u32 hash_idx = hash_32(pid, VK_PID_HT_SHIFT_BIT);
+
+	spin_lock(&vk->ctx_lock);
+
+	/* check if it is in reset, if so, don't allow */
+	if (vk->reset_pid) {
+		dev_err(&vk->pdev->dev,
+			"No context allowed during reset by pid %d\n",
+			vk->reset_pid);
+
+		goto in_reset_exit;
+	}
+
+	for (i = 0; i < ARRAY_SIZE(vk->ctx); i++) {
+		if (!vk->ctx[i].in_use) {
+			vk->ctx[i].in_use = true;
+			ctx = &vk->ctx[i];
+			break;
+		}
+	}
+
+	if (!ctx) {
+		dev_err(&vk->pdev->dev, "All context in use\n");
+
+		goto all_in_use_exit;
+	}
+
+	/* set the pid and insert it to hash table */
+	ctx->pid = pid;
+	ctx->hash_idx = hash_idx;
+	list_add_tail(&ctx->node, &vk->pid_ht[hash_idx].head);
+
+	/* increase kref */
+	kref_get(&vk->kref);
+
+	/* clear counter */
+	atomic_set(&ctx->pend_cnt, 0);
+	atomic_set(&ctx->dma_cnt, 0);
+	init_waitqueue_head(&ctx->rd_wq);
+
+all_in_use_exit:
+in_reset_exit:
+	spin_unlock(&vk->ctx_lock);
+
+	return ctx;
+}
+
+static u16 bcm_vk_get_msg_id(struct bcm_vk *vk)
+{
+	u16 rc = VK_MSG_ID_OVERFLOW;
+	u16 test_bit_count = 0;
+
+	spin_lock(&vk->msg_id_lock);
+	while (test_bit_count < (VK_MSG_ID_BITMAP_SIZE - 1)) {
+		/*
+		 * first time come in this loop, msg_id will be 0
+		 * and the first one tested will be 1.  We skip
+		 * VK_SIMPLEX_MSG_ID (0) for one way host2vk
+		 * communication
+		 */
+		vk->msg_id++;
+		if (vk->msg_id == VK_MSG_ID_BITMAP_SIZE)
+			vk->msg_id = 1;
+
+		if (test_bit(vk->msg_id, vk->bmap)) {
+			test_bit_count++;
+			continue;
+		}
+		rc = vk->msg_id;
+		bitmap_set(vk->bmap, vk->msg_id, 1);
+		break;
+	}
+	spin_unlock(&vk->msg_id_lock);
+
+	return rc;
+}
+
+static int bcm_vk_free_ctx(struct bcm_vk *vk, struct bcm_vk_ctx *ctx)
+{
+	u32 idx;
+	u32 hash_idx;
+	pid_t pid;
+	struct bcm_vk_ctx *entry;
+	int count = 0;
+
+	if (!ctx) {
+		dev_err(&vk->pdev->dev, "NULL context detected\n");
+		return -EINVAL;
+	}
+	idx = ctx->idx;
+	pid = ctx->pid;
+
+	spin_lock(&vk->ctx_lock);
+
+	if (!vk->ctx[idx].in_use) {
+		dev_err(&vk->pdev->dev, "context[%d] not in use!\n", idx);
+	} else {
+		vk->ctx[idx].in_use = false;
+		vk->ctx[idx].miscdev = NULL;
+
+		/* Remove it from hash list and see if it is the last one. */
+		list_del(&ctx->node);
+		hash_idx = ctx->hash_idx;
+		list_for_each_entry(entry, &vk->pid_ht[hash_idx].head, node) {
+			if (entry->pid == pid)
+				count++;
+		}
+	}
+
+	spin_unlock(&vk->ctx_lock);
+
+	return count;
+}
+
+static void bcm_vk_free_wkent(struct device *dev, struct bcm_vk_wkent *entry)
+{
+	int proc_cnt;
+
+	bcm_vk_sg_free(dev, entry->dma, VK_DMA_MAX_ADDRS, &proc_cnt);
+	if (proc_cnt)
+		atomic_dec(&entry->ctx->dma_cnt);
+
+	kfree(entry->to_h_msg);
+	kfree(entry);
+}
+
+static void bcm_vk_drain_all_pend(struct device *dev,
+				  struct bcm_vk_msg_chan *chan,
+				  struct bcm_vk_ctx *ctx)
+{
+	u32 num;
+	struct bcm_vk_wkent *entry, *tmp;
+	struct bcm_vk *vk;
+	struct list_head del_q;
+
+	if (ctx)
+		vk = container_of(ctx->miscdev, struct bcm_vk, miscdev);
+
+	INIT_LIST_HEAD(&del_q);
+	spin_lock(&chan->pendq_lock);
+	for (num = 0; num < chan->q_nr; num++) {
+		list_for_each_entry_safe(entry, tmp, &chan->pendq[num], node) {
+			if ((!ctx) || (entry->ctx->idx == ctx->idx)) {
+				list_move_tail(&entry->node, &del_q);
+			}
+		}
+	}
+	spin_unlock(&chan->pendq_lock);
+
+	/* batch clean up */
+	num = 0;
+	list_for_each_entry_safe(entry, tmp, &del_q, node) {
+		list_del(&entry->node);
+		num++;
+		if (ctx) {
+			struct vk_msg_blk *msg;
+			int bit_set;
+			bool responded;
+			u32 msg_id;
+
+			/* if it is specific ctx, log for any stuck */
+			msg = entry->to_v_msg;
+			msg_id = get_msg_id(msg);
+			bit_set = test_bit(msg_id, vk->bmap);
+			responded = entry->to_h_msg ? true : false;
+			if (num <= batch_log)
+				dev_info(dev,
+					 "Drained: fid %u size %u msg 0x%x(seq-%x) ctx 0x%x[fd-%d] args:[0x%x 0x%x] resp %s, bmap %d\n",
+					 msg->function_id, msg->size,
+					 msg_id, entry->seq_num,
+					 msg->context_id, entry->ctx->idx,
+					 msg->cmd, msg->arg,
+					 responded ? "T" : "F", bit_set);
+			if (responded)
+				atomic_dec(&ctx->pend_cnt);
+			else if (bit_set)
+				bcm_vk_msgid_bitmap_clear(vk, msg_id, 1);
+		}
+		bcm_vk_free_wkent(dev, entry);
+	}
+	if (num && ctx)
+		dev_info(dev, "Total drained items %d [fd-%d]\n",
+			 num, ctx->idx);
+}
+
+void bcm_vk_drain_msg_on_reset(struct bcm_vk *vk)
+{
+	bcm_vk_drain_all_pend(&vk->pdev->dev, &vk->to_v_msg_chan, NULL);
+	bcm_vk_drain_all_pend(&vk->pdev->dev, &vk->to_h_msg_chan, NULL);
+}
+
+/*
+ * Function to sync up the messages queue info that is provided by BAR1
+ */
+int bcm_vk_sync_msgq(struct bcm_vk *vk, bool force_sync)
+{
+	struct bcm_vk_msgq __iomem *msgq;
+	struct device *dev = &vk->pdev->dev;
+	u32 msgq_off;
+	u32 num_q;
+	struct bcm_vk_msg_chan *chan_list[] = {&vk->to_v_msg_chan,
+					       &vk->to_h_msg_chan};
+	struct bcm_vk_msg_chan *chan;
+	int i, j;
+	int ret = 0;
+
+	/*
+	 * If the driver is loaded at startup where vk OS is not up yet,
+	 * the msgq-info may not be available until a later time.  In
+	 * this case, we skip and the sync function is supposed to be
+	 * called again.
+	 */
+	if (!bcm_vk_msgq_marker_valid(vk)) {
+		dev_info(dev, "BAR1 msgq marker not initialized.\n");
+		return -EAGAIN;
+	}
+
+	msgq_off = vkread32(vk, BAR_1, VK_BAR1_MSGQ_CTRL_OFF);
+
+	/* each side is always half the total  */
+	num_q = vkread32(vk, BAR_1, VK_BAR1_MSGQ_NR) / 2;
+	if (!num_q || (num_q > VK_MSGQ_PER_CHAN_MAX)) {
+		dev_err(dev,
+			"Advertised msgq %d error - max %d allowed\n",
+			num_q, VK_MSGQ_PER_CHAN_MAX);
+		return -EINVAL;
+	}
+
+	vk->to_v_msg_chan.q_nr = num_q;
+	vk->to_h_msg_chan.q_nr = num_q;
+
+	/* first msgq location */
+	msgq = vk->bar[BAR_1] + msgq_off;
+
+	/*
+	 * if this function is called when it is already inited,
+	 * something is wrong
+	 */
+	if (bcm_vk_drv_access_ok(vk) && !force_sync) {
+		dev_err(dev, "Msgq info already in sync\n");
+		return -EPERM;
+	}
+
+	for (i = 0; i < ARRAY_SIZE(chan_list); i++) {
+		chan = chan_list[i];
+		memset(chan->sync_qinfo, 0, sizeof(chan->sync_qinfo));
+
+		for (j = 0; j < num_q; j++) {
+			struct bcm_vk_sync_qinfo *qinfo;
+			u32 msgq_start;
+			u32 msgq_size;
+			u32 msgq_nxt;
+			u32 msgq_db_offset, q_db_offset;
+
+			chan->msgq[j] = msgq;
+			msgq_start = readl_relaxed(&msgq->start);
+			msgq_size = readl_relaxed(&msgq->size);
+			msgq_nxt = readl_relaxed(&msgq->nxt);
+			msgq_db_offset = readl_relaxed(&msgq->db_offset);
+			q_db_offset = (msgq_db_offset & ((1 << DB_SHIFT) - 1));
+			if (q_db_offset  == (~msgq_db_offset >> DB_SHIFT))
+				msgq_db_offset = q_db_offset;
+			else
+				/* fall back to default */
+				msgq_db_offset = VK_BAR0_Q_DB_BASE(j);
+
+			dev_info(dev,
+				 "MsgQ[%d] type %d num %d, @ 0x%x, db_offset 0x%x rd_idx %d wr_idx %d, size %d, nxt 0x%x\n",
+				 j,
+				 readw_relaxed(&msgq->type),
+				 readw_relaxed(&msgq->num),
+				 msgq_start,
+				 msgq_db_offset,
+				 readl_relaxed(&msgq->rd_idx),
+				 readl_relaxed(&msgq->wr_idx),
+				 msgq_size,
+				 msgq_nxt);
+
+			qinfo = &chan->sync_qinfo[j];
+			/* formulate and record static info */
+			qinfo->q_start = vk->bar[BAR_1] + msgq_start;
+			qinfo->q_size = msgq_size;
+			/* set low threshold as 50% or 1/2 */
+			qinfo->q_low = qinfo->q_size >> 1;
+			qinfo->q_mask = qinfo->q_size - 1;
+			qinfo->q_db_offset = msgq_db_offset;
+
+			msgq++;
+		}
+	}
+	atomic_set(&vk->msgq_inited, 1);
+
+	return ret;
+}
+
+static int bcm_vk_msg_chan_init(struct bcm_vk_msg_chan *chan)
+{
+	u32 i;
+
+	mutex_init(&chan->msgq_mutex);
+	spin_lock_init(&chan->pendq_lock);
+	for (i = 0; i < VK_MSGQ_MAX_NR; i++)
+		INIT_LIST_HEAD(&chan->pendq[i]);
+
+	return 0;
+}
+
+static void bcm_vk_append_pendq(struct bcm_vk_msg_chan *chan, u16 q_num,
+				struct bcm_vk_wkent *entry)
+{
+	struct bcm_vk_ctx *ctx;
+
+	spin_lock(&chan->pendq_lock);
+	list_add_tail(&entry->node, &chan->pendq[q_num]);
+	if (entry->to_h_msg) {
+		ctx = entry->ctx;
+		atomic_inc(&ctx->pend_cnt);
+		wake_up_interruptible(&ctx->rd_wq);
+	}
+	spin_unlock(&chan->pendq_lock);
+}
+
+static u32 bcm_vk_append_ib_sgl(struct bcm_vk *vk,
+				struct bcm_vk_wkent *entry,
+				struct _vk_data *data,
+				unsigned int num_planes)
+{
+	unsigned int i;
+	unsigned int item_cnt = 0;
+	struct device *dev = &vk->pdev->dev;
+	struct bcm_vk_msg_chan *chan = &vk->to_v_msg_chan;
+	struct vk_msg_blk *msg = &entry->to_v_msg[0];
+	struct bcm_vk_msgq __iomem *msgq;
+	struct bcm_vk_sync_qinfo *qinfo;
+	u32 ib_sgl_size = 0;
+	u8 *buf = (u8 *)&entry->to_v_msg[entry->to_v_blks];
+	u32 avail;
+	u32 q_num;
+
+	/* check if high watermark is hit, and if so, skip */
+	q_num = get_q_num(msg);
+	msgq = chan->msgq[q_num];
+	qinfo = &chan->sync_qinfo[q_num];
+	avail = msgq_avail_space(msgq, qinfo);
+	if (avail < qinfo->q_low) {
+		dev_dbg(dev, "Skip inserting inband SGL, [0x%x/0x%x]\n",
+			avail, qinfo->q_size);
+		return 0;
+	}
+
+	for (i = 0; i < num_planes; i++) {
+		if (data[i].address &&
+		    (ib_sgl_size + data[i].size) <= vk->ib_sgl_size) {
+			item_cnt++;
+			memcpy(buf, entry->dma[i].sglist, data[i].size);
+			ib_sgl_size += data[i].size;
+			buf += data[i].size;
+		}
+	}
+
+	dev_dbg(dev, "Num %u sgl items appended, size 0x%x, room 0x%x\n",
+		item_cnt, ib_sgl_size, vk->ib_sgl_size);
+
+	/* round up size */
+	ib_sgl_size = (ib_sgl_size + VK_MSGQ_BLK_SIZE - 1)
+		       >> VK_MSGQ_BLK_SZ_SHIFT;
+
+	return ib_sgl_size;
+}
+
+void bcm_to_v_q_doorbell(struct bcm_vk *vk, u32 q_num, u32 db_val)
+{
+	struct bcm_vk_msg_chan *chan = &vk->to_v_msg_chan;
+	struct bcm_vk_sync_qinfo *qinfo = &chan->sync_qinfo[q_num];
+
+	vkwrite32(vk, db_val, BAR_0, qinfo->q_db_offset);
+}
+
+static int bcm_to_v_msg_enqueue(struct bcm_vk *vk, struct bcm_vk_wkent *entry)
+{
+	static u32 seq_num;
+	struct bcm_vk_msg_chan *chan = &vk->to_v_msg_chan;
+	struct device *dev = &vk->pdev->dev;
+	struct vk_msg_blk *src = &entry->to_v_msg[0];
+
+	struct vk_msg_blk __iomem *dst;
+	struct bcm_vk_msgq __iomem *msgq;
+	struct bcm_vk_sync_qinfo *qinfo;
+	u32 q_num = get_q_num(src);
+	u32 wr_idx; /* local copy */
+	u32 i;
+	u32 avail;
+	u32 retry;
+
+	if (entry->to_v_blks != src->size + 1) {
+		dev_err(dev, "number of blks %d not matching %d MsgId[0x%x]: func %d ctx 0x%x\n",
+			entry->to_v_blks,
+			src->size + 1,
+			get_msg_id(src),
+			src->function_id,
+			src->context_id);
+		return -EMSGSIZE;
+	}
+
+	msgq = chan->msgq[q_num];
+	qinfo = &chan->sync_qinfo[q_num];
+
+	mutex_lock(&chan->msgq_mutex);
+
+	avail = msgq_avail_space(msgq, qinfo);
+
+	/* if not enough space, return EAGAIN and let app handles it */
+	retry = 0;
+	while ((avail < entry->to_v_blks) &&
+	       (retry++ < BCM_VK_H2VK_ENQ_RETRY)) {
+		mutex_unlock(&chan->msgq_mutex);
+
+		msleep(BCM_VK_H2VK_ENQ_RETRY_DELAY_MS);
+		mutex_lock(&chan->msgq_mutex);
+		avail = msgq_avail_space(msgq, qinfo);
+	}
+	if (retry > BCM_VK_H2VK_ENQ_RETRY) {
+		mutex_unlock(&chan->msgq_mutex);
+		return -EAGAIN;
+	}
+
+	/* at this point, mutex is taken and there is enough space */
+	entry->seq_num = seq_num++; /* update debug seq number */
+	wr_idx = readl_relaxed(&msgq->wr_idx);
+
+	if (wr_idx >= qinfo->q_size) {
+		dev_crit(dev, "Invalid wr_idx 0x%x => max 0x%x!",
+			 wr_idx, qinfo->q_size);
+		bcm_vk_blk_drv_access(vk);
+		bcm_vk_set_host_alert(vk, ERR_LOG_HOST_PCIE_DWN);
+		goto idx_err;
+	}
+
+	dst = msgq_blk_addr(qinfo, wr_idx);
+	for (i = 0; i < entry->to_v_blks; i++) {
+		memcpy_toio(dst, src, sizeof(*dst));
+
+		src++;
+		wr_idx = msgq_inc(qinfo, wr_idx, 1);
+		dst = msgq_blk_addr(qinfo, wr_idx);
+	}
+
+	/* flush the write pointer */
+	writel(wr_idx, &msgq->wr_idx);
+
+	/* log new info for debugging */
+	dev_dbg(dev,
+		"MsgQ[%d] [Rd Wr] = [%d %d] blks inserted %d - Q = [u-%d a-%d]/%d\n",
+		readl_relaxed(&msgq->num),
+		readl_relaxed(&msgq->rd_idx),
+		wr_idx,
+		entry->to_v_blks,
+		msgq_occupied(msgq, qinfo),
+		msgq_avail_space(msgq, qinfo),
+		readl_relaxed(&msgq->size));
+	/*
+	 * press door bell based on queue number. 1 is added to the wr_idx
+	 * to avoid the value of 0 appearing on the VK side to distinguish
+	 * from initial value.
+	 */
+	bcm_to_v_q_doorbell(vk, q_num, wr_idx + 1);
+idx_err:
+	mutex_unlock(&chan->msgq_mutex);
+	return 0;
+}
+
+int bcm_vk_send_shutdown_msg(struct bcm_vk *vk, u32 shut_type,
+			     const pid_t pid, const u32 q_num)
+{
+	int rc = 0;
+	struct bcm_vk_wkent *entry;
+	struct device *dev = &vk->pdev->dev;
+
+	/*
+	 * check if the marker is still good.  Sometimes, the PCIe interface may
+	 * have gone done, and if so and we ship down thing based on broken
+	 * values, kernel may panic.
+	 */
+	if (!bcm_vk_msgq_marker_valid(vk)) {
+		dev_info(dev, "PCIe comm chan - invalid marker (0x%x)!\n",
+			 vkread32(vk, BAR_1, VK_BAR1_MSGQ_DEF_RDY));
+		return -EINVAL;
+	}
+
+	entry = kzalloc(struct_size(entry, to_v_msg, 1), GFP_KERNEL);
+	if (!entry)
+		return -ENOMEM;
+
+	/* fill up necessary data */
+	entry->to_v_msg[0].function_id = VK_FID_SHUTDOWN;
+	set_q_num(&entry->to_v_msg[0], q_num);
+	set_msg_id(&entry->to_v_msg[0], VK_SIMPLEX_MSG_ID);
+	entry->to_v_blks = 1; /* always 1 block */
+
+	entry->to_v_msg[0].cmd = shut_type;
+	entry->to_v_msg[0].arg = pid;
+
+	rc = bcm_to_v_msg_enqueue(vk, entry);
+	if (rc)
+		dev_err(dev,
+			"Sending shutdown message to q %d for pid %d fails.\n",
+			get_q_num(&entry->to_v_msg[0]), pid);
+
+	kfree(entry);
+
+	return rc;
+}
+
+static int bcm_vk_handle_last_sess(struct bcm_vk *vk, const pid_t pid,
+				   const u32 q_num)
+{
+	int rc = 0;
+	struct device *dev = &vk->pdev->dev;
+
+	/*
+	 * don't send down or do anything if message queue is not initialized
+	 * and if it is the reset session, clear it.
+	 */
+	if (!bcm_vk_drv_access_ok(vk)) {
+		if (vk->reset_pid == pid)
+			vk->reset_pid = 0;
+		return -EPERM;
+	}
+
+	dev_dbg(dev, "No more sessions, shut down pid %d\n", pid);
+
+	/* only need to do it if it is not the reset process */
+	if (vk->reset_pid != pid)
+		rc = bcm_vk_send_shutdown_msg(vk, VK_SHUTDOWN_PID, pid, q_num);
+	else
+		/* put reset_pid to 0 if it is exiting last session */
+		vk->reset_pid = 0;
+
+	return rc;
+}
+
+static struct bcm_vk_wkent *bcm_vk_dequeue_pending(struct bcm_vk *vk,
+						   struct bcm_vk_msg_chan *chan,
+						   u16 q_num,
+						   u16 msg_id)
+{
+	struct bcm_vk_wkent *entry = NULL, *iter;
+
+	spin_lock(&chan->pendq_lock);
+	list_for_each_entry(iter, &chan->pendq[q_num], node) {
+		if (get_msg_id(&iter->to_v_msg[0]) == msg_id) {
+			list_del(&iter->node);
+			entry = iter;
+			bcm_vk_msgid_bitmap_clear(vk, msg_id, 1);
+			break;
+		}
+	}
+	spin_unlock(&chan->pendq_lock);
+	return entry;
+}
+
+s32 bcm_to_h_msg_dequeue(struct bcm_vk *vk)
+{
+	struct device *dev = &vk->pdev->dev;
+	struct bcm_vk_msg_chan *chan = &vk->to_h_msg_chan;
+	struct vk_msg_blk *data;
+	struct vk_msg_blk __iomem *src;
+	struct vk_msg_blk *dst;
+	struct bcm_vk_msgq __iomem *msgq;
+	struct bcm_vk_sync_qinfo *qinfo;
+	struct bcm_vk_wkent *entry;
+	u32 rd_idx, wr_idx;
+	u32 q_num, msg_id, j;
+	u32 num_blks;
+	s32 total = 0;
+	int cnt = 0;
+	int msg_processed = 0;
+	int max_msg_to_process;
+	bool exit_loop;
+
+	/*
+	 * drain all the messages from the queues, and find its pending
+	 * entry in the to_v queue, based on msg_id & q_num, and move the
+	 * entry to the to_h pending queue, waiting for user space
+	 * program to extract
+	 */
+	mutex_lock(&chan->msgq_mutex);
+
+	for (q_num = 0; q_num < chan->q_nr; q_num++) {
+		msgq = chan->msgq[q_num];
+		qinfo = &chan->sync_qinfo[q_num];
+		max_msg_to_process = BCM_VK_MSG_PROC_MAX_LOOP * qinfo->q_size;
+
+		rd_idx = readl_relaxed(&msgq->rd_idx);
+		wr_idx = readl_relaxed(&msgq->wr_idx);
+		msg_processed = 0;
+		exit_loop = false;
+		while ((rd_idx != wr_idx) && !exit_loop) {
+			u8 src_size;
+
+			/*
+			 * Make a local copy and get pointer to src blk
+			 * The rd_idx is masked before getting the pointer to
+			 * avoid out of bound access in case the interface goes
+			 * down.  It will end up pointing to the last block in
+			 * the buffer, but subsequent src->size check would be
+			 * able to catch this.
+			 */
+			src = msgq_blk_addr(qinfo, rd_idx & qinfo->q_mask);
+			src_size = readb(&src->size);
+
+			if ((rd_idx >= qinfo->q_size) ||
+			    (src_size > (qinfo->q_size - 1))) {
+				dev_crit(dev,
+					 "Invalid rd_idx 0x%x or size 0x%x => max 0x%x!",
+					 rd_idx, src_size, qinfo->q_size);
+				bcm_vk_blk_drv_access(vk);
+				bcm_vk_set_host_alert(vk,
+						      ERR_LOG_HOST_PCIE_DWN);
+				goto idx_err;
+			}
+
+			num_blks = src_size + 1;
+			data = kzalloc(num_blks * VK_MSGQ_BLK_SIZE, GFP_KERNEL);
+			if (data) {
+				/* copy messages and linearize it */
+				dst = data;
+				for (j = 0; j < num_blks; j++) {
+					memcpy_fromio(dst, src, sizeof(*dst));
+
+					dst++;
+					rd_idx = msgq_inc(qinfo, rd_idx, 1);
+					src = msgq_blk_addr(qinfo, rd_idx);
+				}
+				total++;
+			} else {
+				/*
+				 * if we could not allocate memory in kernel,
+				 * that is fatal.
+				 */
+				dev_crit(dev, "Kernel mem allocation failure.\n");
+				total = -ENOMEM;
+				goto idx_err;
+			}
+
+			/* flush rd pointer after a message is dequeued */
+			writel(rd_idx, &msgq->rd_idx);
+
+			/* log new info for debugging */
+			dev_dbg(dev,
+				"MsgQ[%d] [Rd Wr] = [%d %d] blks extracted %d - Q = [u-%d a-%d]/%d\n",
+				readl_relaxed(&msgq->num),
+				rd_idx,
+				wr_idx,
+				num_blks,
+				msgq_occupied(msgq, qinfo),
+				msgq_avail_space(msgq, qinfo),
+				readl_relaxed(&msgq->size));
+
+			/*
+			 * No need to search if it is an autonomous one-way
+			 * message from driver, as these messages do not bear
+			 * a to_v pending item. Currently, only the shutdown
+			 * message falls into this category.
+			 */
+			if (data->function_id == VK_FID_SHUTDOWN) {
+				kfree(data);
+				continue;
+			}
+
+			msg_id = get_msg_id(data);
+			/* lookup original message in to_v direction */
+			entry = bcm_vk_dequeue_pending(vk,
+						       &vk->to_v_msg_chan,
+						       q_num,
+						       msg_id);
+
+			/*
+			 * if there is message to does not have prior send,
+			 * this is the location to add here
+			 */
+			if (entry) {
+				entry->to_h_blks = num_blks;
+				entry->to_h_msg = data;
+				bcm_vk_append_pendq(&vk->to_h_msg_chan,
+						    q_num, entry);
+
+			} else {
+				if (cnt++ < batch_log)
+					dev_info(dev,
+						 "Could not find MsgId[0x%x] for resp func %d bmap %d\n",
+						 msg_id, data->function_id,
+						 test_bit(msg_id, vk->bmap));
+				kfree(data);
+			}
+			/* Fetch wr_idx to handle more back-to-back events */
+			wr_idx = readl(&msgq->wr_idx);
+
+			/*
+			 * cap the max so that even we try to handle more back-to-back events,
+			 * so that it won't hold CPU too long or in case rd/wr idexes are
+			 * corrupted which triggers infinite looping.
+			 */
+			if (++msg_processed >= max_msg_to_process) {
+				dev_warn(dev, "Q[%d] Per loop processing exceeds %d\n",
+					 q_num, max_msg_to_process);
+				exit_loop = true;
+			}
+		}
+	}
+idx_err:
+	mutex_unlock(&chan->msgq_mutex);
+	dev_dbg(dev, "total %d drained from queues\n", total);
+
+	return total;
+}
+
+/*
+ * init routine for all required data structures
+ */
+static int bcm_vk_data_init(struct bcm_vk *vk)
+{
+	int i;
+
+	spin_lock_init(&vk->ctx_lock);
+	for (i = 0; i < ARRAY_SIZE(vk->ctx); i++) {
+		vk->ctx[i].in_use = false;
+		vk->ctx[i].idx = i;	/* self identity */
+		vk->ctx[i].miscdev = NULL;
+	}
+	spin_lock_init(&vk->msg_id_lock);
+	spin_lock_init(&vk->host_alert_lock);
+	vk->msg_id = 0;
+
+	/* initialize hash table */
+	for (i = 0; i < VK_PID_HT_SZ; i++)
+		INIT_LIST_HEAD(&vk->pid_ht[i].head);
+
+	return 0;
+}
+
+irqreturn_t bcm_vk_msgq_irqhandler(int irq, void *dev_id)
+{
+	struct bcm_vk *vk = dev_id;
+
+	if (!bcm_vk_drv_access_ok(vk)) {
+		dev_err(&vk->pdev->dev,
+			"Interrupt %d received when msgq not inited\n", irq);
+		goto skip_schedule_work;
+	}
+
+	queue_work(vk->wq_thread, &vk->wq_work);
+
+skip_schedule_work:
+	return IRQ_HANDLED;
+}
+
+int bcm_vk_open(struct inode *inode, struct file *p_file)
+{
+	struct bcm_vk_ctx *ctx;
+	struct miscdevice *miscdev = (struct miscdevice *)p_file->private_data;
+	struct bcm_vk *vk = container_of(miscdev, struct bcm_vk, miscdev);
+	struct device *dev = &vk->pdev->dev;
+	int rc = 0;
+
+	/* get a context and set it up for file */
+	ctx = bcm_vk_get_ctx(vk, task_tgid_nr(current));
+	if (!ctx) {
+		dev_err(dev, "Error allocating context\n");
+		rc = -ENOMEM;
+	} else {
+		/*
+		 * set up context and replace private data with context for
+		 * other methods to use.  Reason for the context is because
+		 * it is allowed for multiple sessions to open the sysfs, and
+		 * for each file open, when upper layer query the response,
+		 * only those that are tied to a specific open should be
+		 * returned.  The context->idx will be used for such binding
+		 */
+		ctx->miscdev = miscdev;
+		p_file->private_data = ctx;
+		dev_dbg(dev, "ctx_returned with idx %d, pid %d\n",
+			ctx->idx, ctx->pid);
+	}
+	return rc;
+}
+
+ssize_t bcm_vk_read(struct file *p_file,
+		    char __user *buf,
+		    size_t count,
+		    loff_t *f_pos)
+{
+	ssize_t rc = -ENOMSG;
+	struct bcm_vk_ctx *ctx = p_file->private_data;
+	struct bcm_vk *vk = container_of(ctx->miscdev, struct bcm_vk,
+					 miscdev);
+	struct device *dev = &vk->pdev->dev;
+	struct bcm_vk_msg_chan *chan = &vk->to_h_msg_chan;
+	struct bcm_vk_wkent *entry = NULL, *iter;
+	u32 q_num;
+	u32 rsp_length;
+
+	if (!bcm_vk_drv_access_ok(vk))
+		return -EPERM;
+
+	dev_dbg(dev, "Buf count %zu\n", count);
+
+	/*
+	 * search through the pendq on the to_h chan, and return only those
+	 * that belongs to the same context.  Search is always from the high to
+	 * the low priority queues
+	 */
+	spin_lock(&chan->pendq_lock);
+	for (q_num = 0; q_num < chan->q_nr; q_num++) {
+		list_for_each_entry(iter, &chan->pendq[q_num], node) {
+			if (iter->ctx->idx == ctx->idx) {
+				if (count >=
+				    (iter->to_h_blks * VK_MSGQ_BLK_SIZE)) {
+					list_del(&iter->node);
+					atomic_dec(&ctx->pend_cnt);
+					entry = iter;
+				} else {
+					/* buffer not big enough */
+					rc = -EMSGSIZE;
+				}
+				goto read_loop_exit;
+			}
+		}
+	}
+read_loop_exit:
+	spin_unlock(&chan->pendq_lock);
+
+	if (entry) {
+		/* retrieve the passed down msg_id */
+		set_msg_id(&entry->to_h_msg[0], entry->usr_msg_id);
+		rsp_length = entry->to_h_blks * VK_MSGQ_BLK_SIZE;
+		if (copy_to_user(buf, entry->to_h_msg, rsp_length) == 0)
+			rc = rsp_length;
+
+		bcm_vk_free_wkent(dev, entry);
+	} else if (rc == -EMSGSIZE) {
+		struct vk_msg_blk tmp_msg = entry->to_h_msg[0];
+
+		/*
+		 * in this case, return just the first block, so
+		 * that app knows what size it is looking for.
+		 */
+		set_msg_id(&tmp_msg, entry->usr_msg_id);
+		tmp_msg.size = entry->to_h_blks - 1;
+		if (copy_to_user(buf, &tmp_msg, VK_MSGQ_BLK_SIZE) != 0) {
+			dev_err(dev, "Error return 1st block in -EMSGSIZE\n");
+			rc = -EFAULT;
+		}
+	}
+	return rc;
+}
+
+ssize_t bcm_vk_write(struct file *p_file,
+		     const char __user *buf,
+		     size_t count,
+		     loff_t *f_pos)
+{
+	ssize_t rc;
+	struct bcm_vk_ctx *ctx = p_file->private_data;
+	struct bcm_vk *vk = container_of(ctx->miscdev, struct bcm_vk,
+					 miscdev);
+	struct bcm_vk_msgq __iomem *msgq;
+	struct device *dev = &vk->pdev->dev;
+	struct bcm_vk_wkent *entry;
+	u32 sgl_extra_blks;
+	u32 q_num;
+	u32 msg_size;
+	u32 msgq_size;
+
+	if (!bcm_vk_drv_access_ok(vk))
+		return -EPERM;
+
+	dev_dbg(dev, "Msg count %zu\n", count);
+
+	/* first, do sanity check where count should be multiple of basic blk */
+	if (count & (VK_MSGQ_BLK_SIZE - 1)) {
+		dev_err(dev, "Failure with size %zu not multiple of %zu\n",
+			count, VK_MSGQ_BLK_SIZE);
+		rc = -EINVAL;
+		goto write_err;
+	}
+
+	/* allocate the work entry + buffer for size count and inband sgl */
+	entry = kzalloc(sizeof(*entry) + count + vk->ib_sgl_size,
+			GFP_KERNEL);
+	if (!entry) {
+		rc = -ENOMEM;
+		goto write_err;
+	}
+
+	/* now copy msg from user space, and then formulate the work entry */
+	if (copy_from_user(&entry->to_v_msg[0], buf, count)) {
+		rc = -EFAULT;
+		goto write_free_ent;
+	}
+
+	entry->to_v_blks = count >> VK_MSGQ_BLK_SZ_SHIFT;
+	entry->ctx = ctx;
+
+	/* do a check on the blk size which could not exceed queue space */
+	q_num = get_q_num(&entry->to_v_msg[0]);
+	msgq = vk->to_v_msg_chan.msgq[q_num];
+	msgq_size = readl_relaxed(&msgq->size);
+	if (entry->to_v_blks + (vk->ib_sgl_size >> VK_MSGQ_BLK_SZ_SHIFT)
+	    > (msgq_size - 1)) {
+		dev_err(dev, "Blk size %d exceed max queue size allowed %d\n",
+			entry->to_v_blks, msgq_size - 1);
+		rc = -EINVAL;
+		goto write_free_ent;
+	}
+
+	/* Use internal message id */
+	entry->usr_msg_id = get_msg_id(&entry->to_v_msg[0]);
+	rc = bcm_vk_get_msg_id(vk);
+	if (rc == VK_MSG_ID_OVERFLOW) {
+		dev_err(dev, "msg_id overflow\n");
+		rc = -EOVERFLOW;
+		goto write_free_ent;
+	}
+	set_msg_id(&entry->to_v_msg[0], rc);
+	ctx->q_num = q_num;
+
+	dev_dbg(dev,
+		"[Q-%d]Message ctx id %d, usr_msg_id 0x%x sent msg_id 0x%x\n",
+		ctx->q_num, ctx->idx, entry->usr_msg_id,
+		get_msg_id(&entry->to_v_msg[0]));
+
+	if (entry->to_v_msg[0].function_id == VK_FID_TRANS_BUF) {
+		/* Convert any pointers to sg list */
+		unsigned int num_planes;
+		int dir;
+		struct _vk_data *data;
+
+		/*
+		 * check if we are in reset, if so, no buffer transfer is
+		 * allowed and return error.
+		 */
+		if (vk->reset_pid) {
+			dev_dbg(dev, "No Transfer allowed during reset, pid %d.\n",
+				ctx->pid);
+			rc = -EACCES;
+			goto write_free_msgid;
+		}
+
+		num_planes = entry->to_v_msg[0].cmd & VK_CMD_PLANES_MASK;
+		if ((entry->to_v_msg[0].cmd & VK_CMD_MASK) == VK_CMD_DOWNLOAD)
+			dir = DMA_FROM_DEVICE;
+		else
+			dir = DMA_TO_DEVICE;
+
+		/* Calculate vk_data location */
+		/* Go to end of the message */
+		msg_size = entry->to_v_msg[0].size;
+		if (msg_size > entry->to_v_blks) {
+			rc = -EMSGSIZE;
+			goto write_free_msgid;
+		}
+
+		data = (struct _vk_data *)&entry->to_v_msg[msg_size + 1];
+
+		/* Now back up to the start of the pointers */
+		data -= num_planes;
+
+		/* Convert user addresses to DMA SG List */
+		rc = bcm_vk_sg_alloc(dev, entry->dma, dir, data, num_planes);
+		if (rc)
+			goto write_free_msgid;
+
+		atomic_inc(&ctx->dma_cnt);
+		/* try to embed inband sgl */
+		sgl_extra_blks = bcm_vk_append_ib_sgl(vk, entry, data,
+						      num_planes);
+		entry->to_v_blks += sgl_extra_blks;
+		entry->to_v_msg[0].size += sgl_extra_blks;
+	} else if (entry->to_v_msg[0].function_id == VK_FID_INIT &&
+		   entry->to_v_msg[0].context_id == VK_NEW_CTX) {
+		/*
+		 * Init happens in 2 stages, only the first stage contains the
+		 * pid that needs translating.
+		 */
+		pid_t org_pid, pid;
+
+		/*
+		 * translate the pid into the unique host space as user
+		 * may run sessions inside containers or process
+		 * namespaces.
+		 */
+#define VK_MSG_PID_MASK 0xffffff00
+#define VK_MSG_PID_SH   8
+		org_pid = (entry->to_v_msg[0].arg & VK_MSG_PID_MASK)
+			   >> VK_MSG_PID_SH;
+
+		pid = task_tgid_nr(current);
+		entry->to_v_msg[0].arg =
+			(entry->to_v_msg[0].arg & ~VK_MSG_PID_MASK) |
+			(pid << VK_MSG_PID_SH);
+		if (org_pid != pid)
+			dev_dbg(dev, "In PID 0x%x(%d), converted PID 0x%x(%d)\n",
+				org_pid, org_pid, pid, pid);
+	}
+
+	/*
+	 * store work entry to pending queue until a response is received.
+	 * This needs to be done before enqueuing the message
+	 */
+	bcm_vk_append_pendq(&vk->to_v_msg_chan, q_num, entry);
+
+	rc = bcm_to_v_msg_enqueue(vk, entry);
+	if (rc) {
+		dev_err(dev, "Fail to enqueue msg to to_v queue\n");
+
+		/* remove message from pending list */
+		entry = bcm_vk_dequeue_pending
+			       (vk,
+				&vk->to_v_msg_chan,
+				q_num,
+				get_msg_id(&entry->to_v_msg[0]));
+		goto write_free_ent;
+	}
+
+	return count;
+
+write_free_msgid:
+	bcm_vk_msgid_bitmap_clear(vk, get_msg_id(&entry->to_v_msg[0]), 1);
+write_free_ent:
+	kfree(entry);
+write_err:
+	return rc;
+}
+
+__poll_t bcm_vk_poll(struct file *p_file, struct poll_table_struct *wait)
+{
+	__poll_t ret = 0;
+	int cnt;
+	struct bcm_vk_ctx *ctx = p_file->private_data;
+	struct bcm_vk *vk = container_of(ctx->miscdev, struct bcm_vk, miscdev);
+	struct device *dev = &vk->pdev->dev;
+
+	poll_wait(p_file, &ctx->rd_wq, wait);
+
+	cnt = atomic_read(&ctx->pend_cnt);
+	if (cnt) {
+		ret = (__force __poll_t)(POLLIN | POLLRDNORM);
+		if (cnt < 0) {
+			dev_err(dev, "Error cnt %d, setting back to 0", cnt);
+			atomic_set(&ctx->pend_cnt, 0);
+		}
+	}
+
+	return ret;
+}
+
+int bcm_vk_release(struct inode *inode, struct file *p_file)
+{
+	int ret;
+	struct bcm_vk_ctx *ctx = p_file->private_data;
+	struct bcm_vk *vk = container_of(ctx->miscdev, struct bcm_vk, miscdev);
+	struct device *dev = &vk->pdev->dev;
+	pid_t pid = ctx->pid;
+	int dma_cnt;
+	unsigned long timeout, start_time;
+
+	/*
+	 * if there are outstanding DMA transactions, need to delay long enough
+	 * to ensure that the card side would have stopped touching the host buffer
+	 * and its SGL list.  A race condition could happen if the host app is killed
+	 * abruptly, eg kill -9, while some DMA transfer orders are still inflight.
+	 * Nothing could be done except for a delay as host side is running in a
+	 * completely async fashion.
+	 */
+	start_time = jiffies;
+	timeout = start_time + msecs_to_jiffies(BCM_VK_DMA_DRAIN_MAX_MS);
+	do {
+		if (time_after(jiffies, timeout)) {
+			dev_warn(dev, "%d dma still pending for [fd-%d] pid %d\n",
+				 dma_cnt, ctx->idx, pid);
+			break;
+		}
+		dma_cnt = atomic_read(&ctx->dma_cnt);
+		cpu_relax();
+		cond_resched();
+	} while (dma_cnt);
+	dev_dbg(dev, "Draining for [fd-%d] pid %d - delay %d ms\n",
+		ctx->idx, pid, jiffies_to_msecs(jiffies - start_time));
+
+	bcm_vk_drain_all_pend(&vk->pdev->dev, &vk->to_v_msg_chan, ctx);
+	bcm_vk_drain_all_pend(&vk->pdev->dev, &vk->to_h_msg_chan, ctx);
+
+	ret = bcm_vk_free_ctx(vk, ctx);
+	if (ret == 0)
+		ret = bcm_vk_handle_last_sess(vk, pid, ctx->q_num);
+	else
+		ret = 0;
+
+	kref_put(&vk->kref, bcm_vk_release_data);
+
+	return ret;
+}
+
+int bcm_vk_msg_init(struct bcm_vk *vk)
+{
+	struct device *dev = &vk->pdev->dev;
+	int ret;
+
+	if (bcm_vk_data_init(vk)) {
+		dev_err(dev, "Error initializing internal data structures\n");
+		return -EINVAL;
+	}
+
+	if (bcm_vk_msg_chan_init(&vk->to_v_msg_chan) ||
+	    bcm_vk_msg_chan_init(&vk->to_h_msg_chan)) {
+		dev_err(dev, "Error initializing communication channel\n");
+		return -EIO;
+	}
+
+	/* read msgq info if ready */
+	ret = bcm_vk_sync_msgq(vk, false);
+	if (ret && (ret != -EAGAIN)) {
+		dev_err(dev, "Error reading comm msg Q info\n");
+		return -EIO;
+	}
+
+	return 0;
+}
+
+void bcm_vk_msg_remove(struct bcm_vk *vk)
+{
+	bcm_vk_blk_drv_access(vk);
+
+	/* drain all pending items */
+	bcm_vk_drain_all_pend(&vk->pdev->dev, &vk->to_v_msg_chan, NULL);
+	bcm_vk_drain_all_pend(&vk->pdev->dev, &vk->to_h_msg_chan, NULL);
+}
+