net: fec: ptp: avoid register access when ipg clock is disabled

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 <[email protected]>

---
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(+)

drivers/net/ethernet/freescale/fec_ptp.c +7 -1

index 2e344aada4c6..1753807cbf97 100644
@@ -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

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 <[email protected]>

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

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

Quoted 20 lines · Heiko Thiery

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 <[email protected]>

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

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

Sorry for the noise. But just realized that I sent a v3 version of the patch but forgot to update the subject line (still v2). Should I resend it with the correct subject?

Acked-by Richard Cochran <[email protected]>