[PATCH v2 1/1] net: fec: ptp: avoid register access when ipg clock is disabled

Heiko Thiery
2021-02-25T21:16:59Z

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>
---
v2:
- add mutex (thanks to Richard)

v3:
I did a mistake and did not test properly
- add parenteses
- fix the used variable

drivers/net/ethernet/freescale/fec_ptp.c | 7 +++++++
1 file changed, 7 insertions(+)

diff --git a/drivers/net/ethernet/freescale/fec_ptp.c b/drivers/net/ethernet/freescale/fec_ptp.c
index 2e344aada4c6..1753807cbf97 100644
--- a/drivers/net/ethernet/freescale/fec_ptp.c
+++ b/drivers/net/ethernet/freescale/fec_ptp.c
@@ -377,9 +377,16 @@ static int fec_ptp_gettime(struct ptp_clock_info *ptp, struct timespec64 *ts)
u64 ns;
unsigned long flags;

+ mutex_lock(&adapter->ptp_clk_mutex);
+ /* Check the ptp clock */
+ if (!adapter->ptp_clk_on) {
+ mutex_unlock(&adapter->ptp_clk_mutex);
+ return -EINVAL;
+ }
spin_lock_irqsave(&adapter->tmreg_lock, flags);
ns = timecounter_read(&adapter->tc);
spin_unlock_irqrestore(&adapter->tmreg_lock, flags);
+ mutex_unlock(&adapter->ptp_clk_mutex);

*ts = ns_to_timespec64(ns);

--
2.30.0