[PATCH iwl-next 4/8] ixgbe: increase SECRX_RDY polling frequency in ixgbe_disable_rx_buff_generic

[Aleksandr Loktionov <aleksandr.loktionov@intel.com>]

From: Maciej Rabeda <maciej.rabeda@intel.com>

ixgbe_disable_rx_buff_generic polls for SECRX_RDY with 40 iterations
and a 1000 us (1 ms) busy-wait per iteration via udelay(), giving an
exact total wait of 40 ms.  On fast hardware the security block is
typically ready well under 1 ms, so each iteration wastes up to
999 us of stalled initialization time.

Replace udelay(1000) with usleep_range(10, 20) and raise the iteration
limit to 4000.  Because usleep_range(min, max) is guaranteed to sleep
at least 'min' microseconds, 4000 * 10 us preserves the original 40 ms
minimum wait before timeout.  The worst-case is now ~80 ms (4000 * 20
us) plus scheduler latency, which is acceptable since SECRX_RDY
failing to assert is a non-fatal informational condition (the function
just logs a debug message).

On platforms where SECRX_RDY asserts quickly this reduces the typical
stall from up to ~1 ms per iteration to ~10-20 us.  The function is
called only from process context, so usleep_range is appropriate.

Signed-off-by: Maciej Rabeda <maciej.rabeda@intel.com>
Signed-off-by: Aleksandr Loktionov <aleksandr.loktionov@intel.com>
---
 drivers/net/ethernet/intel/ixgbe/ixgbe_common.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe_common.c b/drivers/net/ethernet/intel/ixgbe/ixgbe_common.c
index 3ea6765..c85618c 100644
--- a/drivers/net/ethernet/intel/ixgbe/ixgbe_common.c
+++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_common.c
@@ -2683,7 +2683,7 @@ int prot_autoc_write_generic(struct ixgbe_hw *hw, u32 reg_val, bool locked)
  **/
 int ixgbe_disable_rx_buff_generic(struct ixgbe_hw *hw)
 {
-#define IXGBE_MAX_SECRX_POLL 40
+#define IXGBE_MAX_SECRX_POLL 4000
 	int i;
 	int secrxreg;
 
@@ -2695,8 +2695,7 @@ int ixgbe_disable_rx_buff_generic(struct ixgbe_hw *hw)
 		if (secrxreg & IXGBE_SECRXSTAT_SECRX_RDY)
 			break;
 		else
-			/* Use interrupt-safe sleep just in case */
-			udelay(1000);
+			usleep_range(10, 20);
 	}
 
 	/* For informational purposes only */
-- 
2.52.0