[PATCH v3 23/27] net/txgbe: replace rte_atomic32 with stdatomic

[Stephen Hemminger]

The swfw_busy flag guarding the AML SW-FW mailbox is a one-bit lock,
so convert it to RTE_ATOMIC(bool) and replace the legacy
test-and-set / clear pair with explicit acquire-release:

  rte_atomic32_test_and_set ->
      rte_atomic_exchange_explicit(.., true, acquire)
  rte_atomic32_clear        ->
      rte_atomic_store_explicit(.., false, release)

Acquire on the take pairs with release on the drop, so accesses
inside the critical section are synchronized between successive
holders. Default zero-initialization of struct txgbe_hw still
gives swfw_busy = false, so no init site needs updating.

Note: the code for the AML spinlock had a bug because
old rte_atomic32_test_set return value was not what the code
expected. This patch fixes that. A seperate patch for stable
has been sent upstream. (Drop this note from commit message
when rebasing after the fix is merged).

Signed-off-by: Stephen Hemminger <stephen at networkplumber.org>
---
 drivers/net/txgbe/base/txgbe_mng.c  | 4 ++--
 drivers/net/txgbe/base/txgbe_type.h | 2 +-
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/net/txgbe/base/txgbe_mng.c b/drivers/net/txgbe/base/txgbe_mng.c
index a1974820b6..c58e1d6589 100644
--- a/drivers/net/txgbe/base/txgbe_mng.c
+++ b/drivers/net/txgbe/base/txgbe_mng.c
@@ -185,7 +185,7 @@ txgbe_host_interface_command_aml(struct txgbe_hw *hw, u32 *buffer,
 	}
 
 	/* try to get lock */
-	while (rte_atomic32_test_and_set(&hw->swfw_busy)) {
+	while (rte_atomic_exchange_explicit(&hw->swfw_busy, true, rte_memory_order_acquire)) {
 		timeout--;
 		if (!timeout)
 			return TXGBE_ERR_TIMEOUT;
@@ -266,7 +266,7 @@ txgbe_host_interface_command_aml(struct txgbe_hw *hw, u32 *buffer,
 	/* index++, index replace txgbe_hic_hdr.checksum */
 	hw->swfw_index = resp->index == TXGBE_HIC_HDR_INDEX_MAX ?
 					0 : resp->index + 1;
-	rte_atomic32_clear(&hw->swfw_busy);
+	rte_atomic_store_explicit(&hw->swfw_busy, false, rte_memory_order_release);
 
 	return err;
 }
diff --git a/drivers/net/txgbe/base/txgbe_type.h b/drivers/net/txgbe/base/txgbe_type.h
index ede780321f..d3c82d51a4 100644
--- a/drivers/net/txgbe/base/txgbe_type.h
+++ b/drivers/net/txgbe/base/txgbe_type.h
@@ -880,7 +880,7 @@ struct txgbe_hw {
 	rte_spinlock_t phy_lock;
 	/*amlite: new SW-FW mbox */
 	u8 swfw_index;
-	rte_atomic32_t swfw_busy;
+	RTE_ATOMIC(bool) swfw_busy;
 	u32 fec_mode;
 	u32 cur_fec_link;
 };
-- 
2.53.0