[PATCH v2 4/6] net: qrtr: Hold runtime PM during active data path operations

[Krishna Chaitanya Chundru <krishna.chundru@oss.qualcomm.com>]

The QRTR MHI transport driver does not coordinate with runtime PM, which
allows the underlying MHI controller to be runtime-suspended while
transmit, receive, or RX buffer refill operations are in progress. This can
lead to stalled transfers or failed buffer queueing once runtime PM is
enabled in the MHI core.

Add runtime PM reference counting around TX, RX, and buffer management
operations to keep the controller active for the duration of each critical
section. Enable runtime PM during probe and take explicit references around
these data path operations.

Signed-off-by: Krishna Chaitanya Chundru <krishna.chundru@oss.qualcomm.com>
---
 net/qrtr/mhi.c | 57 ++++++++++++++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 54 insertions(+), 3 deletions(-)

diff --git a/net/qrtr/mhi.c b/net/qrtr/mhi.c
index 80e341d2f8a4..cba7a5daf7a4 100644
--- a/net/qrtr/mhi.c
+++ b/net/qrtr/mhi.c
@@ -6,6 +6,7 @@
 #include <linux/mhi.h>
 #include <linux/mod_devicetable.h>
 #include <linux/module.h>
+#include <linux/pm_runtime.h>
 #include <linux/skbuff.h>
 #include <net/sock.h>
 
@@ -38,11 +39,20 @@ static void qcom_mhi_qrtr_dl_callback(struct mhi_device *mhi_dev,
 	if (rc == -EINVAL)
 		dev_err(qdev->dev, "invalid ipcrouter packet\n");
 
+	rc = pm_runtime_get(&qdev->mhi_dev->dev);
+	if (rc < 0 && rc != -EINPROGRESS) {
+		dev_err(&mhi_dev->dev, "pm_runtime_get failed %d\n", rc);
+		pm_runtime_put_noidle(&qdev->mhi_dev->dev);
+		return;
+	}
+
 	/* Done with the buffer, now recycle it for future use */
 	rc = mhi_queue_buf(mhi_dev, DMA_FROM_DEVICE, mhi_res->buf_addr,
 			   mhi_dev->mhi_cntrl->buffer_len, MHI_EOT);
 	if (rc)
 		dev_err(&mhi_dev->dev, "Failed to recycle the buffer: %d\n", rc);
+
+	pm_runtime_put(&mhi_dev->dev);
 }
 
 /* From QRTR to MHI */
@@ -54,6 +64,8 @@ static void qcom_mhi_qrtr_ul_callback(struct mhi_device *mhi_dev,
 	if (skb->sk)
 		sock_put(skb->sk);
 	consume_skb(skb);
+
+	pm_runtime_put(&mhi_dev->dev);
 }
 
 /* Send data over MHI */
@@ -69,13 +81,21 @@ static int qcom_mhi_qrtr_send(struct qrtr_endpoint *ep, struct sk_buff *skb)
 	if (rc)
 		goto free_skb;
 
+	rc = pm_runtime_resume_and_get(&qdev->mhi_dev->dev);
+	if (rc) {
+		dev_err(&qdev->mhi_dev->dev, "pm_runtime_resume_and_get failed %d\n", rc);
+		goto free_skb;
+	}
+
 	rc = mhi_queue_skb(qdev->mhi_dev, DMA_TO_DEVICE, skb, skb->len,
 			   MHI_EOT);
 	if (rc)
-		goto free_skb;
+		goto runtime_put;
 
 	return rc;
 
+runtime_put:
+	pm_runtime_put(&qdev->mhi_dev->dev);
 free_skb:
 	if (skb->sk)
 		sock_put(skb->sk);
@@ -90,20 +110,30 @@ static int qcom_mhi_qrtr_queue_dl_buffers(struct mhi_device *mhi_dev)
 	void *buf;
 	int ret;
 
+	ret = pm_runtime_resume_and_get(&mhi_dev->dev);
+	if (ret) {
+		dev_err(&mhi_dev->dev, "pm_runtime_resume_and_get failed %d\n", ret);
+		return ret;
+	}
+
 	free_desc = mhi_get_free_desc_count(mhi_dev, DMA_FROM_DEVICE);
 	while (free_desc--) {
 		buf = devm_kmalloc(&mhi_dev->dev, mhi_dev->mhi_cntrl->buffer_len, GFP_KERNEL);
-		if (!buf)
+		if (!buf) {
+			pm_runtime_put(&mhi_dev->dev);
 			return -ENOMEM;
+		}
 
 		ret = mhi_queue_buf(mhi_dev, DMA_FROM_DEVICE, buf, mhi_dev->mhi_cntrl->buffer_len,
 				    MHI_EOT);
 		if (ret) {
 			dev_err(&mhi_dev->dev, "Failed to queue buffer: %d\n", ret);
+			pm_runtime_put(&mhi_dev->dev);
 			return ret;
 		}
 	}
 
+	pm_runtime_put(&mhi_dev->dev);
 	return 0;
 }
 
@@ -121,12 +151,22 @@ static int qcom_mhi_qrtr_probe(struct mhi_device *mhi_dev,
 	qdev->dev = &mhi_dev->dev;
 	qdev->ep.xmit = qcom_mhi_qrtr_send;
 
+	pm_runtime_no_callbacks(&mhi_dev->dev);
+	rc = devm_pm_runtime_set_active_enabled(&mhi_dev->dev);
+	if (rc)
+		return rc;
+
+	rc = pm_runtime_resume_and_get(&mhi_dev->dev);
+	if (rc) {
+		dev_err(&mhi_dev->dev, "pm_runtime_resume_and_get failed %d\n", rc);
+		return rc;
+	}
 	dev_set_drvdata(&mhi_dev->dev, qdev);
 
 	/* start channels */
 	rc = mhi_prepare_for_transfer(mhi_dev);
 	if (rc)
-		return rc;
+		goto runtime_put;
 
 	rc = qrtr_endpoint_register(&qdev->ep, QRTR_EP_NID_AUTO);
 	if (rc)
@@ -138,12 +178,15 @@ static int qcom_mhi_qrtr_probe(struct mhi_device *mhi_dev,
 
 	dev_dbg(qdev->dev, "Qualcomm MHI QRTR driver probed\n");
 
+	pm_runtime_put(&mhi_dev->dev);
 	return 0;
 
 err_unregister:
 	qrtr_endpoint_unregister(&qdev->ep);
 err_unprepare:
 	mhi_unprepare_from_transfer(mhi_dev);
+runtime_put:
+	pm_runtime_put(&mhi_dev->dev);
 
 	return rc;
 }
@@ -151,10 +194,18 @@ static int qcom_mhi_qrtr_probe(struct mhi_device *mhi_dev,
 static void qcom_mhi_qrtr_remove(struct mhi_device *mhi_dev)
 {
 	struct qrtr_mhi_dev *qdev = dev_get_drvdata(&mhi_dev->dev);
+	int err;
+
+	err = pm_runtime_resume_and_get(&mhi_dev->dev);
+	if (err)
+		dev_err(&mhi_dev->dev, "pm_runtime_resume_and_get failed %d\n", err);
 
 	qrtr_endpoint_unregister(&qdev->ep);
 	mhi_unprepare_from_transfer(mhi_dev);
 	dev_set_drvdata(&mhi_dev->dev, NULL);
+
+	if (!err)
+		pm_runtime_put(&mhi_dev->dev);
 }
 
 static const struct mhi_device_id qcom_mhi_qrtr_id_table[] = {

-- 
2.34.1