netdev - [PATCH net-next v2 2/7] ice: Remove gettime HW semaphore

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Date:   Tue, 22 Nov 2022 14:10:42 -0800
From:   Tony Nguyen <anthony.l.nguyen@...el.com>
To:     davem@...emloft.net, kuba@...nel.org, pabeni@...hat.com,
        edumazet@...gle.com
Cc:     Karol Kolacinski <karol.kolacinski@...el.com>,
        netdev@...r.kernel.org, anthony.l.nguyen@...el.com,
        richardcochran@...il.com, Gurucharan G <gurucharanx.g@...el.com>
Subject: [PATCH net-next v2 2/7] ice: Remove gettime HW semaphore

From: Karol Kolacinski <karol.kolacinski@...el.com>

Reading the time should not block other accesses to the PTP hardware.
There isn't a significant risk of reading bad values while another
thread is modifying the clock. Removing the hardware lock around the
gettime allows multiple application threads to read the clock time with
less contention.

Signed-off-by: Karol Kolacinski <karol.kolacinski@...el.com>
Tested-by: Gurucharan G <gurucharanx.g@...el.com> (A Contingent worker at Intel)
Signed-off-by: Tony Nguyen <anthony.l.nguyen@...el.com>
---
 drivers/net/ethernet/intel/ice/ice_ptp.c | 31 +++---------------------
 1 file changed, 3 insertions(+), 28 deletions(-)

diff --git a/drivers/net/ethernet/intel/ice/ice_ptp.c b/drivers/net/ethernet/intel/ice/ice_ptp.c
index 5cf198a33e26..d1bab1876249 100644
--- a/drivers/net/ethernet/intel/ice/ice_ptp.c
+++ b/drivers/net/ethernet/intel/ice/ice_ptp.c
@@ -979,26 +979,6 @@ static void ice_ptp_reset_cached_phctime(struct ice_pf *pf)
 	ice_ptp_flush_tx_tracker(pf, &pf->ptp.port.tx);
 }
 
-/**
- * ice_ptp_read_time - Read the time from the device
- * @pf: Board private structure
- * @ts: timespec structure to hold the current time value
- * @sts: Optional parameter for holding a pair of system timestamps from
- *       the system clock. Will be ignored if NULL is given.
- *
- * This function reads the source clock registers and stores them in a timespec.
- * However, since the registers are 64 bits of nanoseconds, we must convert the
- * result to a timespec before we can return.
- */
-static void
-ice_ptp_read_time(struct ice_pf *pf, struct timespec64 *ts,
-		  struct ptp_system_timestamp *sts)
-{
-	u64 time_ns = ice_ptp_read_src_clk_reg(pf, sts);
-
-	*ts = ns_to_timespec64(time_ns);
-}
-
 /**
  * ice_ptp_write_init - Set PHC time to provided value
  * @pf: Board private structure
@@ -1789,15 +1769,10 @@ ice_ptp_gettimex64(struct ptp_clock_info *info, struct timespec64 *ts,
 		   struct ptp_system_timestamp *sts)
 {
 	struct ice_pf *pf = ptp_info_to_pf(info);
-	struct ice_hw *hw = &pf->hw;
+	u64 time_ns;
 
-	if (!ice_ptp_lock(hw)) {
-		dev_err(ice_pf_to_dev(pf), "PTP failed to get time\n");
-		return -EBUSY;
-	}
-
-	ice_ptp_read_time(pf, ts, sts);
-	ice_ptp_unlock(hw);
+	time_ns = ice_ptp_read_src_clk_reg(pf, sts);
+	*ts = ns_to_timespec64(time_ns);
 
 	return 0;
 }
-- 
2.35.1