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From:   Heiko Thiery <heiko.thiery@gmail.com>
To:     linux-kernel@vger.kernel.org, netdev@vger.kernel.org
Cc:     Jakub Kicinski <kuba@kernel.org>,
        "David S . Miller" <davem@davemloft.net>,
        Fugang Duan <fugang.duan@nxp.com>,
        Heiko Thiery <heiko.thiery@gmail.com>
Subject: [PATCH 1/1] net: fec: ptp: avoid register access when ipg clock is disabled
Date:   Sat, 20 Feb 2021 07:56:55 +0100
Message-Id: <20210220065654.25598-1-heiko.thiery@gmail.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

When accessing the timecounter register on an i.MX8MQ the kernel hangs.
This is only the case when the interface is down. This can be reproduced
by reading with 'phc_ctrl eth0 get'.

Like described in the change in 91c0d987a9788dcc5fe26baafd73bf9242b68900
the igp clock is disabled when the interface is down and leads to a
system hang.

So we check if the ptp clock status before reading the timecounter
register.

Signed-off-by: Heiko Thiery <heiko.thiery@gmail.com>
---
 drivers/net/ethernet/freescale/fec_ptp.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/net/ethernet/freescale/fec_ptp.c b/drivers/net/ethernet/freescale/fec_ptp.c
index 2e344aada4c6..c9882083da02 100644
--- a/drivers/net/ethernet/freescale/fec_ptp.c
+++ b/drivers/net/ethernet/freescale/fec_ptp.c
@@ -377,6 +377,9 @@ static int fec_ptp_gettime(struct ptp_clock_info *ptp, struct timespec64 *ts)
 	u64 ns;
 	unsigned long flags;
 
+	/* Check the ptp clock */
+	if (!adapter->ptp_clk_on)
+		return -EINVAL;
 	spin_lock_irqsave(&adapter->tmreg_lock, flags);
 	ns = timecounter_read(&adapter->tc);
 	spin_unlock_irqrestore(&adapter->tmreg_lock, flags);
-- 
2.30.0