linux-kernel - [PATCH 3/4] net: mhi_net: Implement runtime PM support

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Message-Id: <20251201-mhi_runtimepm-v1-3-fab94399ca75@oss.qualcomm.com>
Date: Mon, 01 Dec 2025 18:13:19 +0530
From: Krishna Chaitanya Chundru <krishna.chundru@....qualcomm.com>
To: Manivannan Sadhasivam <mani@...nel.org>,
        Jeff Hugo <jeff.hugo@....qualcomm.com>,
        Carl Vanderlip <carl.vanderlip@....qualcomm.com>,
        Oded Gabbay <ogabbay@...nel.org>, Jeff Johnson <jjohnson@...nel.org>,
        Andrew Lunn <andrew+netdev@...n.ch>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>
Cc: mhi@...ts.linux.dev, linux-arm-msm@...r.kernel.org,
        linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        linux-wireless@...r.kernel.org, ath11k@...ts.infradead.org,
        ath12k@...ts.infradead.org, netdev@...r.kernel.org,
        mayank.rana@....qualcomm.com, quic_vbadigan@...cinc.com,
        vivek.pernamitta@....qualcomm.com,
        Krishna Chaitanya Chundru <krishna.chundru@....qualcomm.com>
Subject: [PATCH 3/4] net: mhi_net: Implement runtime PM support

Add runtime power management support to the mhi_net driver to align with
the updated MHI framework, which expects runtime PM to be enabled by client
drivers. This ensures the controller remains active during data transfers
and can autosuspend when idle.

The driver now uses pm_runtime_get() and pm_runtime_put() around
transmit, receive, and buffer refill operations. Runtime PM is initialized
during probe with autosuspend enabled and a 100ms delay. The device is
marked with pm_runtime_no_callbacks() to notify PM framework that there
are no callbacks for this driver.

Signed-off-by: Krishna Chaitanya Chundru <krishna.chundru@....qualcomm.com>
---
 drivers/net/mhi_net.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/drivers/net/mhi_net.c b/drivers/net/mhi_net.c
index ae169929a9d8e449b5a427993abf68e8d032fae2..c5c697f29e69e9bc874b6cfff4699de12a4af114 100644
--- a/drivers/net/mhi_net.c
+++ b/drivers/net/mhi_net.c
@@ -9,6 +9,7 @@
 #include <linux/mod_devicetable.h>
 #include <linux/module.h>
 #include <linux/netdevice.h>
+#include <linux/pm_runtime.h>
 #include <linux/skbuff.h>
 #include <linux/u64_stats_sync.h>
 
@@ -76,6 +77,7 @@ static netdev_tx_t mhi_ndo_xmit(struct sk_buff *skb, struct net_device *ndev)
 	struct mhi_device *mdev = mhi_netdev->mdev;
 	int err;
 
+	pm_runtime_get(&mdev->dev);
 	err = mhi_queue_skb(mdev, DMA_TO_DEVICE, skb, skb->len, MHI_EOT);
 	if (unlikely(err)) {
 		net_err_ratelimited("%s: Failed to queue TX buf (%d)\n",
@@ -94,6 +96,7 @@ static netdev_tx_t mhi_ndo_xmit(struct sk_buff *skb, struct net_device *ndev)
 	u64_stats_inc(&mhi_netdev->stats.tx_dropped);
 	u64_stats_update_end(&mhi_netdev->stats.tx_syncp);
 
+	pm_runtime_put_autosuspend(&mdev->dev);
 	return NETDEV_TX_OK;
 }
 
@@ -261,6 +264,7 @@ static void mhi_net_ul_callback(struct mhi_device *mhi_dev,
 	}
 	u64_stats_update_end(&mhi_netdev->stats.tx_syncp);
 
+	pm_runtime_put_autosuspend(&mdev->dev);
 	if (netif_queue_stopped(ndev) && !mhi_queue_is_full(mdev, DMA_TO_DEVICE))
 		netif_wake_queue(ndev);
 }
@@ -277,6 +281,7 @@ static void mhi_net_rx_refill_work(struct work_struct *work)
 
 	size = mhi_netdev->mru ? mhi_netdev->mru : READ_ONCE(ndev->mtu);
 
+	pm_runtime_get_sync(&mdev->dev);
 	while (!mhi_queue_is_full(mdev, DMA_FROM_DEVICE)) {
 		skb = netdev_alloc_skb(ndev, size);
 		if (unlikely(!skb))
@@ -296,6 +301,7 @@ static void mhi_net_rx_refill_work(struct work_struct *work)
 		cond_resched();
 	}
 
+	pm_runtime_put_autosuspend(&mdev->dev);
 	/* If we're still starved of rx buffers, reschedule later */
 	if (mhi_get_free_desc_count(mdev, DMA_FROM_DEVICE) == mhi_netdev->rx_queue_sz)
 		schedule_delayed_work(&mhi_netdev->rx_refill, HZ / 2);
@@ -362,12 +368,19 @@ static int mhi_net_probe(struct mhi_device *mhi_dev,
 
 	SET_NETDEV_DEV(ndev, &mhi_dev->dev);
 
+	pm_runtime_no_callbacks(&mhi_dev->dev);
+	devm_pm_runtime_set_active_enabled(&mhi_dev->dev);
+	pm_runtime_set_autosuspend_delay(&mhi_dev->dev, 100);
+	pm_runtime_use_autosuspend(&mhi_dev->dev);
+	pm_runtime_get(&mhi_dev->dev);
 	err = mhi_net_newlink(mhi_dev, ndev);
 	if (err) {
 		free_netdev(ndev);
+		pm_runtime_put_autosuspend(&mhi_dev->dev);
 		return err;
 	}
 
+	pm_runtime_put_autosuspend(&mhi_dev->dev);
 	return 0;
 }
 

-- 
2.34.1