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From:   Bhaumik Bhatt <bbhatt@codeaurora.org>
To:     manivannan.sadhasivam@linaro.org
Cc:     bqiang@codeaurora.org, linux-arm-msm@vger.kernel.org,
        hemantk@codeaurora.org, clew@codeaurora.org,
        linux-kernel@vger.kernel.org, Bhaumik Bhatt <bbhatt@codeaurora.org>
Subject: [PATCH] net: qrtr: mhi: synchronize qrtr and mhi preparation
Date:   Tue, 20 Jul 2021 18:42:58 -0700
Message-Id: <1626831778-31796-1-git-send-email-bbhatt@codeaurora.org>
Precedence: bulk

A dl callback can be received anytime after mhi_prepare_for_transfer
has been called. There is a window where the callback may happen
before the probe initializes the qrtr_mhi_dev state. Move the
mhi_prepare_for_transfer call after the registering the endpoint.

Once moved, the reverse can happen where qrtr will try to send a packet
before the channels are prepared. Add a wait in the sending path to
ensure the channels are prepared before trying to do a ul transfer.

Fixes: a2e2cc0dbb11 ("net: qrtr: Start MHI channels during init")
Signed-off-by: Bhaumik Bhatt <bbhatt@codeaurora.org>
---
 net/qrtr/mhi.c | 20 +++++++++++++++-----
 1 file changed, 15 insertions(+), 5 deletions(-)

diff --git a/net/qrtr/mhi.c b/net/qrtr/mhi.c
index 29b4fa3..22b0395 100644
--- a/net/qrtr/mhi.c
+++ b/net/qrtr/mhi.c
@@ -15,6 +15,7 @@ struct qrtr_mhi_dev {
 	struct qrtr_endpoint ep;
 	struct mhi_device *mhi_dev;
 	struct device *dev;
+	struct completion ready;
 };
 
 /* From MHI to QRTR */
@@ -50,6 +51,10 @@ static int qcom_mhi_qrtr_send(struct qrtr_endpoint *ep, struct sk_buff *skb)
 	struct qrtr_mhi_dev *qdev = container_of(ep, struct qrtr_mhi_dev, ep);
 	int rc;
 
+	rc = wait_for_completion_interruptible(&qdev->ready);
+	if (rc)
+		goto free_skb;
+
 	if (skb->sk)
 		sock_hold(skb->sk);
 
@@ -78,11 +83,6 @@ static int qcom_mhi_qrtr_probe(struct mhi_device *mhi_dev,
 	struct qrtr_mhi_dev *qdev;
 	int rc;
 
-	/* start channels */
-	rc = mhi_prepare_for_transfer(mhi_dev, MHI_CH_INBOUND_ALLOC_BUFS);
-	if (rc)
-		return rc;
-
 	qdev = devm_kzalloc(&mhi_dev->dev, sizeof(*qdev), GFP_KERNEL);
 	if (!qdev)
 		return -ENOMEM;
@@ -90,12 +90,22 @@ static int qcom_mhi_qrtr_probe(struct mhi_device *mhi_dev,
 	qdev->mhi_dev = mhi_dev;
 	qdev->dev = &mhi_dev->dev;
 	qdev->ep.xmit = qcom_mhi_qrtr_send;
+	init_completion(&qdev->ready);
 
 	dev_set_drvdata(&mhi_dev->dev, qdev);
 	rc = qrtr_endpoint_register(&qdev->ep, QRTR_EP_NID_AUTO);
 	if (rc)
 		return rc;
 
+	/* start channels */
+	rc = mhi_prepare_for_transfer(mhi_dev, MHI_CH_INBOUND_ALLOC_BUFS);
+	if (rc) {
+		qrtr_endpoint_unregister(&qdev->ep);
+		dev_set_drvdata(&mhi_dev->dev, NULL);
+		return rc;
+	}
+
+	complete_all(&qdev->ready);
 	dev_dbg(qdev->dev, "Qualcomm MHI QRTR driver probed\n");
 
 	return 0;
-- 
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