[PATCH iwl-net v5 3/8] ice: Cache struct ice_hw pointer for split register reads

[Sergey Temerkhanov <sergey.temerkhanov@intel.com>]

Cache the primary ice_hw pointer to ensure consistency between
calls (both parts of a value will be read from the same NAC).
ice_get_primary_hw() will never return NULL, but during the
ctrl_pf cleanup there may be a case when one call will return
the pointer to the ctrl_pf->hw and the subsequent one - to the
pf->hw which generally are not the same.
Struct ice_hw is embedded in the struct ice_pf so it is protected
by the same critical section - no additional synchronization is
needed.

Fixes: e2193f9f9ec9 ("ice: enable timesync operation on 2xNAC E825 devices")
Signed-off-by: Sergey Temerkhanov <sergey.temerkhanov@intel.com>
Reviewed-by: Aleksandr Loktionov <aleksandr.loktionov@intel.com>
Reviewed-by: Arkadiusz Kubalewski <arkadiusz.kubalewski@intel.com>
Tested-by: Frederick Lawler <fred@cloudflare.com>
---
 drivers/net/ethernet/intel/ice/ice_ptp_hw.c | 17 +++++++++++++----
 1 file changed, 13 insertions(+), 4 deletions(-)

diff --git a/drivers/net/ethernet/intel/ice/ice_ptp_hw.c b/drivers/net/ethernet/intel/ice/ice_ptp_hw.c
index 0e138390f8c8..38e90a68ba78 100644
--- a/drivers/net/ethernet/intel/ice/ice_ptp_hw.c
+++ b/drivers/net/ethernet/intel/ice/ice_ptp_hw.c
@@ -4,6 +4,7 @@
 #include <linux/cleanup.h>
 #include <linux/delay.h>
 #include <linux/iopoll.h>
+#include "ice.h"
 #include "ice_common.h"
 #include "ice_ptp_hw.h"
 #include "ice_ptp_consts.h"
@@ -2014,10 +2015,14 @@ static int ice_read_phy_and_phc_time_eth56g(struct ice_hw *hw, u8 port,
 		zo = rd32(hw, GLTSYN_SHTIME_0(tmr_idx));
 		lo = rd32(hw, GLTSYN_SHTIME_L(tmr_idx));
 	} else {
+		struct ice_hw *pri_hw;
+
 		guard(rcu)();
 
-		zo = rd32(ice_get_primary_hw(pf), GLTSYN_SHTIME_0(tmr_idx));
-		lo = rd32(ice_get_primary_hw(pf), GLTSYN_SHTIME_L(tmr_idx));
+		pri_hw = ice_get_primary_hw(pf);
+
+		zo = rd32(pri_hw, GLTSYN_SHTIME_0(tmr_idx));
+		lo = rd32(pri_hw, GLTSYN_SHTIME_L(tmr_idx));
 	}
 	*phc_time = (u64)lo << 32 | zo;
 
@@ -2187,12 +2192,16 @@ int ice_start_phy_timer_eth56g(struct ice_hw *hw, u8 port)
 		lo = rd32(hw, GLTSYN_INCVAL_L(tmr_idx));
 		hi = rd32(hw, GLTSYN_INCVAL_H(tmr_idx));
 	} else {
+		struct ice_hw *pri_hw;
+
 		/* cleanup.h advises against mixing goto with scoped helpers,
 		 * and this function unwinds the PTP semaphore with goto below.
 		 */
 		rcu_read_lock();
-		lo = rd32(ice_get_primary_hw(pf), GLTSYN_INCVAL_L(tmr_idx));
-		hi = rd32(ice_get_primary_hw(pf), GLTSYN_INCVAL_H(tmr_idx));
+		pri_hw = ice_get_primary_hw(pf);
+
+		lo = rd32(pri_hw, GLTSYN_INCVAL_L(tmr_idx));
+		hi = rd32(pri_hw, GLTSYN_INCVAL_H(tmr_idx));
 		rcu_read_unlock();
 	}
 	incval = (u64)hi << 32 | lo;
-- 
2.53.0