ice: track hardware stat registers past rollover

Currently, ice_stat_update32 and ice_stat_update40 will limit the
value of the software statistic to 32 or 40 bits wide, depending on
which register is being read.

This means that if a driver is running for a long time, the displayed
software register values will roll over to zero at 40 bits or 32 bits.

This occurs because the functions directly assign the difference between
the previous value and current value of the hardware statistic.

Instead, add this value to the current software statistic, and then
update the previous value.

In this way, each time ice_stat_update40 or ice_stat_update32 are
called, they will increment the software tracking value by the
difference of the hardware register from its last read. The software
tracking value will correctly count up until it overflows a u64.

The only requirement is that the ice_stat_update functions be called at
least once each time the hardware register overflows.

While we're fixing ice_stat_update40, modify it to use rd64 instead of
two calls to rd32. Additionally, drop the now unnecessary hireg
function parameter.

Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>

1 files changed, 35 insertions, 22 deletions

diff --git a/drivers/net/ethernet/intel/ice/ice_common.c b/drivers/net/ethernet/intel/ice/ice_common.c
index 2e0731c1e1a3..4be3559de207 100644
--- a/drivers/net/ethernet/intel/ice/ice_common.c
+++ b/drivers/net/ethernet/intel/ice/ice_common.c
@@ -3240,40 +3240,44 @@ void ice_replay_post(struct ice_hw *hw)
 /**
  * ice_stat_update40 - read 40 bit stat from the chip and update stat values
  * @hw: ptr to the hardware info
- * @hireg: high 32 bit HW register to read from
- * @loreg: low 32 bit HW register to read from
+ * @reg: offset of 64 bit HW register to read from
  * @prev_stat_loaded: bool to specify if previous stats are loaded
  * @prev_stat: ptr to previous loaded stat value
  * @cur_stat: ptr to current stat value
  */
 void
-ice_stat_update40(struct ice_hw *hw, u32 hireg, u32 loreg,
-		  bool prev_stat_loaded, u64 *prev_stat, u64 *cur_stat)
+ice_stat_update40(struct ice_hw *hw, u32 reg, bool prev_stat_loaded,
+		  u64 *prev_stat, u64 *cur_stat)
 {
-	u64 new_data;
-
-	new_data = rd32(hw, loreg);
-	new_data |= ((u64)(rd32(hw, hireg) & 0xFFFF)) << 32;
+	u64 new_data = rd64(hw, reg) & (BIT_ULL(40) - 1);
 
 	/* device stats are not reset at PFR, they likely will not be zeroed
-	 * when the driver starts. So save the first values read and use them as
-	 * offsets to be subtracted from the raw values in order to report stats
-	 * that count from zero.
+	 * when the driver starts. Thus, save the value from the first read
+	 * without adding to the statistic value so that we report stats which
+	 * count up from zero.
 	 */
-	if (!prev_stat_loaded)
+	if (!prev_stat_loaded) {
 		*prev_stat = new_data;
+		return;
+	}
+
+	/* Calculate the difference between the new and old values, and then
+	 * add it to the software stat value.
+	 */
 	if (new_data >= *prev_stat)
-		*cur_stat = new_data - *prev_stat;
+		*cur_stat += new_data - *prev_stat;
 	else
 		/* to manage the potential roll-over */
-		*cur_stat = (new_data + BIT_ULL(40)) - *prev_stat;
-	*cur_stat &= 0xFFFFFFFFFFULL;
+		*cur_stat += (new_data + BIT_ULL(40)) - *prev_stat;
+
+	/* Update the previously stored value to prepare for next read */
+	*prev_stat = new_data;
 }
 
 /**
  * ice_stat_update32 - read 32 bit stat from the chip and update stat values
  * @hw: ptr to the hardware info
- * @reg: HW register to read from
+ * @reg: offset of HW register to read from
  * @prev_stat_loaded: bool to specify if previous stats are loaded
  * @prev_stat: ptr to previous loaded stat value
  * @cur_stat: ptr to current stat value
@@ -3287,17 +3291,26 @@ ice_stat_update32(struct ice_hw *hw, u32 reg, bool prev_stat_loaded,
 	new_data = rd32(hw, reg);
 
 	/* device stats are not reset at PFR, they likely will not be zeroed
-	 * when the driver starts. So save the first values read and use them as
-	 * offsets to be subtracted from the raw values in order to report stats
-	 * that count from zero.
+	 * when the driver starts. Thus, save the value from the first read
+	 * without adding to the statistic value so that we report stats which
+	 * count up from zero.
 	 */
-	if (!prev_stat_loaded)
+	if (!prev_stat_loaded) {
 		*prev_stat = new_data;
+		return;
+	}
+
+	/* Calculate the difference between the new and old values, and then
+	 * add it to the software stat value.
+	 */
 	if (new_data >= *prev_stat)
-		*cur_stat = new_data - *prev_stat;
+		*cur_stat += new_data - *prev_stat;
 	else
 		/* to manage the potential roll-over */
-		*cur_stat = (new_data + BIT_ULL(32)) - *prev_stat;
+		*cur_stat += (new_data + BIT_ULL(32)) - *prev_stat;
+
+	/* Update the previously stored value to prepare for next read */
+	*prev_stat = new_data;
 }
 
 /**