[PATCH V1 6/6] rpmsg: glink: Send READ_NOTIFY command in FIFO full case

[Deepak Kumar Singh <deesin@xxxxxxxxxxxxxx>]

From: Arun Kumar Neelakantam <aneela@xxxxxxxxxxxxxx>

The current design sleeps unconditionally in TX FIFO full case and
wakeup only after sleep timer expires which adds random delays in
clients TX path.

Avoid sleep and use READ_NOTIFY command so that writer can be woken up
when remote notifies about read completion by sending IRQ.

Signed-off-by: Deepak Kumar Singh <deesin@xxxxxxxxxxxxxx>
Signed-off-by: Arun Kumar Neelakantam <aneela@xxxxxxxxxxxxxx>
---
 drivers/rpmsg/qcom_glink_native.c | 36 +++++++++++++++++++++++++++++++++++-
 1 file changed, 35 insertions(+), 1 deletion(-)

diff --git a/drivers/rpmsg/qcom_glink_native.c b/drivers/rpmsg/qcom_glink_native.c
index efaf32d..098039d 100644
--- a/drivers/rpmsg/qcom_glink_native.c
+++ b/drivers/rpmsg/qcom_glink_native.c
@@ -92,6 +92,8 @@ struct glink_core_rx_intent {
  * @rcids:	idr of all channels with a known remote channel id
  * @features:	remote features
  * @intentless:	flag to indicate that there is no intent
+ * @tx_avail_notify: Waitqueue for pending tx tasks
+ * @sent_read_notify: flag to check cmd sent or not
  */
 struct qcom_glink {
 	struct device *dev;
@@ -118,6 +120,8 @@ struct qcom_glink {
 	unsigned long features;
 
 	bool intentless;
+	wait_queue_head_t tx_avail_notify;
+	bool sent_read_notify;
 };
 
 enum {
@@ -301,6 +305,20 @@ static void qcom_glink_tx_write(struct qcom_glink *glink,
 	glink->tx_pipe->write(glink->tx_pipe, hdr, hlen, data, dlen);
 }
 
+static void qcom_glink_send_read_notify(struct qcom_glink *glink)
+{
+	struct glink_msg msg;
+
+	msg.cmd = cpu_to_le16(RPM_CMD_READ_NOTIF);
+	msg.param1 = 0;
+	msg.param2 = 0;
+
+	qcom_glink_tx_write(glink, &msg, sizeof(msg), NULL, 0);
+
+	mbox_send_message(glink->mbox_chan, NULL);
+	mbox_client_txdone(glink->mbox_chan, 0);
+}
+
 static int qcom_glink_tx(struct qcom_glink *glink,
 			 const void *hdr, size_t hlen,
 			 const void *data, size_t dlen, bool wait)
@@ -321,12 +339,21 @@ static int qcom_glink_tx(struct qcom_glink *glink,
 			goto out;
 		}
 
+		if (!glink->sent_read_notify) {
+			glink->sent_read_notify = true;
+			qcom_glink_send_read_notify(glink);
+		}
+
 		/* Wait without holding the tx_lock */
 		spin_unlock_irqrestore(&glink->tx_lock, flags);
 
-		usleep_range(10000, 15000);
+		wait_event_timeout(glink->tx_avail_notify,
+				qcom_glink_tx_avail(glink) >= tlen, 10 * HZ);
 
 		spin_lock_irqsave(&glink->tx_lock, flags);
+
+		if (qcom_glink_tx_avail(glink) >= tlen)
+			glink->sent_read_notify = false;
 	}
 
 	qcom_glink_tx_write(glink, hdr, hlen, data, dlen);
@@ -1000,6 +1027,9 @@ static irqreturn_t qcom_glink_native_intr(int irq, void *data)
 	unsigned int cmd;
 	int ret = 0;
 
+	/* To wakeup any blocking writers */
+	wake_up_all(&glink->tx_avail_notify);
+
 	for (;;) {
 		avail = qcom_glink_rx_avail(glink);
 		if (avail < sizeof(msg))
@@ -1542,6 +1572,9 @@ static void qcom_glink_rx_close_ack(struct qcom_glink *glink, unsigned int lcid)
 	struct glink_channel *channel;
 	unsigned long flags;
 
+	/* To wakeup any blocking writers */
+	wake_up_all(&glink->tx_avail_notify);
+
 	spin_lock_irqsave(&glink->idr_lock, flags);
 	channel = idr_find(&glink->lcids, lcid);
 	if (WARN(!channel, "close ack on unknown channel\n")) {
@@ -1658,6 +1691,7 @@ struct qcom_glink *qcom_glink_native_probe(struct device *dev,
 	spin_lock_init(&glink->rx_lock);
 	INIT_LIST_HEAD(&glink->rx_queue);
 	INIT_WORK(&glink->rx_work, qcom_glink_work);
+	init_waitqueue_head(&glink->tx_avail_notify);
 
 	spin_lock_init(&glink->idr_lock);
 	idr_init(&glink->lcids);
-- 
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