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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, Sven Van Asbroeck <thesven73@gmail.com>,
        Jakub Kicinski <kuba@kernel.org>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 5.9 162/255] lan743x: fix "BUG: invalid wait context" when setting rx mode
Date:   Tue, 17 Nov 2020 14:05:02 +0100
Message-Id: <20201117122146.822611086@linuxfoundation.org>
In-Reply-To: <20201117122138.925150709@linuxfoundation.org>
References: <20201117122138.925150709@linuxfoundation.org>
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From: Sven Van Asbroeck <thesven73@gmail.com>

[ Upstream commit 2b52a4b65bc8f14520fe6e996ea7fb3f7e400761 ]

In the net core, the struct net_device_ops -> ndo_set_rx_mode()
callback is called with the dev->addr_list_lock spinlock held.

However, this driver's ndo_set_rx_mode callback eventually calls
lan743x_dp_write(), which acquires a mutex. Mutex acquisition
may sleep, and this is not allowed when holding a spinlock.

Fix by removing the dp_lock mutex entirely. Its purpose is to
prevent concurrent accesses to the data port. No concurrent
accesses are possible, because the dev->addr_list_lock
spinlock in the core only lets through one thread at a time.

Fixes: 23f0703c125b ("lan743x: Add main source files for new lan743x driver")
Signed-off-by: Sven Van Asbroeck <thesven73@gmail.com>
Link: https://lore.kernel.org/r/20201109203828.5115-1-TheSven73@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/net/ethernet/microchip/lan743x_main.c | 12 +++---------
 drivers/net/ethernet/microchip/lan743x_main.h |  3 ---
 2 files changed, 3 insertions(+), 12 deletions(-)

diff --git a/drivers/net/ethernet/microchip/lan743x_main.c b/drivers/net/ethernet/microchip/lan743x_main.c
index be58a941965b1..6c25c7c8b7cf8 100644
--- a/drivers/net/ethernet/microchip/lan743x_main.c
+++ b/drivers/net/ethernet/microchip/lan743x_main.c
@@ -675,14 +675,12 @@ clean_up:
 static int lan743x_dp_write(struct lan743x_adapter *adapter,
 			    u32 select, u32 addr, u32 length, u32 *buf)
 {
-	int ret = -EIO;
 	u32 dp_sel;
 	int i;
 
-	mutex_lock(&adapter->dp_lock);
 	if (lan743x_csr_wait_for_bit(adapter, DP_SEL, DP_SEL_DPRDY_,
 				     1, 40, 100, 100))
-		goto unlock;
+		return -EIO;
 	dp_sel = lan743x_csr_read(adapter, DP_SEL);
 	dp_sel &= ~DP_SEL_MASK_;
 	dp_sel |= select;
@@ -694,13 +692,10 @@ static int lan743x_dp_write(struct lan743x_adapter *adapter,
 		lan743x_csr_write(adapter, DP_CMD, DP_CMD_WRITE_);
 		if (lan743x_csr_wait_for_bit(adapter, DP_SEL, DP_SEL_DPRDY_,
 					     1, 40, 100, 100))
-			goto unlock;
+			return -EIO;
 	}
-	ret = 0;
 
-unlock:
-	mutex_unlock(&adapter->dp_lock);
-	return ret;
+	return 0;
 }
 
 static u32 lan743x_mac_mii_access(u16 id, u16 index, int read)
@@ -2737,7 +2732,6 @@ static int lan743x_hardware_init(struct lan743x_adapter *adapter,
 
 	adapter->intr.irq = adapter->pdev->irq;
 	lan743x_csr_write(adapter, INT_EN_CLR, 0xFFFFFFFF);
-	mutex_init(&adapter->dp_lock);
 
 	ret = lan743x_gpio_init(adapter);
 	if (ret)
diff --git a/drivers/net/ethernet/microchip/lan743x_main.h b/drivers/net/ethernet/microchip/lan743x_main.h
index c61a404113179..a536f4a4994df 100644
--- a/drivers/net/ethernet/microchip/lan743x_main.h
+++ b/drivers/net/ethernet/microchip/lan743x_main.h
@@ -712,9 +712,6 @@ struct lan743x_adapter {
 	struct lan743x_csr      csr;
 	struct lan743x_intr     intr;
 
-	/* lock, used to prevent concurrent access to data port */
-	struct mutex		dp_lock;
-
 	struct lan743x_gpio	gpio;
 	struct lan743x_ptp	ptp;
 
-- 
2.27.0