[Intel-wired-lan] [PATCH iwl-net v1 5/5] igc: Add lock preventing multiple simultaneous PTM transactions

[christopher . s . hall]

From: Christopher S M Hall <christopher.s.h...@intel.com>

Add a mutex around the PTM transaction to prevent multiple transactors

Multiple processes try to initiate a PTM transaction, one or all may
fail. This can be reproduced by running two instances of the
following:

$ sudo phc2sys -O 0 -i tsn0 -m

PHC2SYS exits with:

"ioctl PTP_OFFSET_PRECISE: Connection timed out" when the PTM transaction
 fails

Note: Normally two instance of PHC2SYS will not run, but one process
 should not break another.

Fixes: a90ec8483732 ("igc: Add support for PTP getcrosststamp()")
Signed-off-by: Christopher S M Hall <christopher.s.h...@intel.com>
---
 drivers/net/ethernet/intel/igc/igc.h     |  1 +
 drivers/net/ethernet/intel/igc/igc_ptp.c | 12 ++++++++++--
 2 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/intel/igc/igc.h 
b/drivers/net/ethernet/intel/igc/igc.h
index c38b4d0f00ce..fbac02c79178 100644
--- a/drivers/net/ethernet/intel/igc/igc.h
+++ b/drivers/net/ethernet/intel/igc/igc.h
@@ -315,6 +315,7 @@ struct igc_adapter {
        struct timespec64 prev_ptp_time; /* Pre-reset PTP clock */
        ktime_t ptp_reset_start; /* Reset time in clock mono */
        struct system_time_snapshot snapshot;
+       struct mutex ptm_lock; /* Only allow one PTM transaction at a time */
 
        char fw_version[32];
 
diff --git a/drivers/net/ethernet/intel/igc/igc_ptp.c 
b/drivers/net/ethernet/intel/igc/igc_ptp.c
index f770e39650ef..c70a6393c210 100644
--- a/drivers/net/ethernet/intel/igc/igc_ptp.c
+++ b/drivers/net/ethernet/intel/igc/igc_ptp.c
@@ -1068,9 +1068,16 @@ static int igc_ptp_getcrosststamp(struct ptp_clock_info 
*ptp,
 {
        struct igc_adapter *adapter = container_of(ptp, struct igc_adapter,
                                                   ptp_caps);
+       int ret;
 
-       return get_device_system_crosststamp(igc_phc_get_syncdevicetime,
-                                            adapter, &adapter->snapshot, cts);
+       /* This blocks until any in progress PTM transactions complete */
+       mutex_lock(&adapter->ptm_lock);
+
+       ret = get_device_system_crosststamp(igc_phc_get_syncdevicetime,
+                                           adapter, &adapter->snapshot, cts);
+       mutex_unlock(&adapter->ptm_lock);
+
+       return ret;
 }
 
 static int igc_ptp_getcyclesx64(struct ptp_clock_info *ptp,
@@ -1302,6 +1309,7 @@ void igc_ptp_reset(struct igc_adapter *adapter)
                wr32(IGC_PTM_CTRL, ctrl);
 
                /* Force the first cycle to run. */
+               mutex_init(&adapter->ptm_lock);
                igc_ptm_trigger(hw);
 
                if (readx_poll_timeout_atomic(rd32, IGC_PTM_STAT, stat,
-- 
2.34.1