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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Loic Poulain <loic.poulain@linaro.org>,
        Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Subject: [PATCH 5.12 006/384] bus: mhi: core: Fix MHI runtime_pm behavior
Date:   Mon, 10 May 2021 12:16:35 +0200
Message-Id: <20210510102015.083891508@linuxfoundation.org>
In-Reply-To: <20210510102014.849075526@linuxfoundation.org>
References: <20210510102014.849075526@linuxfoundation.org>
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From: Loic Poulain <loic.poulain@linaro.org>

commit 4547a749be997eb12ea7edcf361ec2a5329f7aec upstream.

This change ensures that PM reference is always get during packet
queueing and released either after queuing completion (RX) or once
the buffer has been consumed (TX). This guarantees proper update for
underlying MHI controller runtime status (e.g. last_busy timestamp)
and prevents suspend to be triggered while TX packets are flying,
or before we completed update of the RX ring.

Signed-off-by: Loic Poulain <loic.poulain@linaro.org>
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Link: https://lore.kernel.org/r/1617700315-12492-1-git-send-email-loic.poulain@linaro.org
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/bus/mhi/core/main.c |   21 ++++++++++++++++-----
 1 file changed, 16 insertions(+), 5 deletions(-)

--- a/drivers/bus/mhi/core/main.c
+++ b/drivers/bus/mhi/core/main.c
@@ -589,8 +589,11 @@ static int parse_xfer_event(struct mhi_c
 			/* notify client */
 			mhi_chan->xfer_cb(mhi_chan->mhi_dev, &result);
 
-			if (mhi_chan->dir == DMA_TO_DEVICE)
+			if (mhi_chan->dir == DMA_TO_DEVICE) {
 				atomic_dec(&mhi_cntrl->pending_pkts);
+				/* Release the reference got from mhi_queue() */
+				mhi_cntrl->runtime_put(mhi_cntrl);
+			}
 
 			/*
 			 * Recycle the buffer if buffer is pre-allocated,
@@ -1062,9 +1065,11 @@ static int mhi_queue(struct mhi_device *
 	if (unlikely(ret))
 		goto exit_unlock;
 
-	/* trigger M3 exit if necessary */
-	if (MHI_PM_IN_SUSPEND_STATE(mhi_cntrl->pm_state))
-		mhi_trigger_resume(mhi_cntrl);
+	/* Packet is queued, take a usage ref to exit M3 if necessary
+	 * for host->device buffer, balanced put is done on buffer completion
+	 * for device->host buffer, balanced put is after ringing the DB
+	 */
+	mhi_cntrl->runtime_get(mhi_cntrl);
 
 	/* Assert dev_wake (to exit/prevent M1/M2)*/
 	mhi_cntrl->wake_toggle(mhi_cntrl);
@@ -1079,6 +1084,9 @@ static int mhi_queue(struct mhi_device *
 
 	mhi_ring_chan_db(mhi_cntrl, mhi_chan);
 
+	if (dir == DMA_FROM_DEVICE)
+		mhi_cntrl->runtime_put(mhi_cntrl);
+
 exit_unlock:
 	read_unlock_irqrestore(&mhi_cntrl->pm_lock, flags);
 
@@ -1470,8 +1478,11 @@ static void mhi_reset_data_chan(struct m
 	while (tre_ring->rp != tre_ring->wp) {
 		struct mhi_buf_info *buf_info = buf_ring->rp;
 
-		if (mhi_chan->dir == DMA_TO_DEVICE)
+		if (mhi_chan->dir == DMA_TO_DEVICE) {
 			atomic_dec(&mhi_cntrl->pending_pkts);
+			/* Release the reference got from mhi_queue() */
+			mhi_cntrl->runtime_put(mhi_cntrl);
+		}
 
 		if (!buf_info->pre_mapped)
 			mhi_cntrl->unmap_single(mhi_cntrl, buf_info);