[PATCH v2] ath10k: Replace ioread with mb to drain write buffer

[Peter Oh]

Using ioread() to perform draining write buffer is excessive.
Use compact API, mb(), that intended to be used for the case.
It reduces total 14 CPU clocks per interrupt.

Signed-off-by: Peter Oh <poh at qca.qualcomm.com>
---
 drivers/net/wireless/ath/ath10k/pci.c | 12 ++++--------
 1 file changed, 4 insertions(+), 8 deletions(-)

diff --git a/drivers/net/wireless/ath/ath10k/pci.c b/drivers/net/wireless/ath/ath10k/pci.c
index e6972b0..f1e6980 100644
--- a/drivers/net/wireless/ath/ath10k/pci.c
+++ b/drivers/net/wireless/ath/ath10k/pci.c
@@ -353,10 +353,8 @@ static void ath10k_pci_disable_and_clear_legacy_irq(struct ath10k *ar)
 	ath10k_pci_write32(ar, SOC_CORE_BASE_ADDRESS + PCIE_INTR_CLR_ADDRESS,
 			   PCIE_INTR_FIRMWARE_MASK | PCIE_INTR_CE_MASK_ALL);
 
-	/* IMPORTANT: this extra read transaction is required to
-	 * flush the posted write buffer. */
-	(void)ath10k_pci_read32(ar, SOC_CORE_BASE_ADDRESS +
-				PCIE_INTR_ENABLE_ADDRESS);
+	/* drain write buffer */
+	mb();
 }
 
 static void ath10k_pci_enable_legacy_irq(struct ath10k *ar)
@@ -365,10 +363,8 @@ static void ath10k_pci_enable_legacy_irq(struct ath10k *ar)
 			   PCIE_INTR_ENABLE_ADDRESS,
 			   PCIE_INTR_FIRMWARE_MASK | PCIE_INTR_CE_MASK_ALL);
 
-	/* IMPORTANT: this extra read transaction is required to
-	 * flush the posted write buffer. */
-	(void)ath10k_pci_read32(ar, SOC_CORE_BASE_ADDRESS +
-				PCIE_INTR_ENABLE_ADDRESS);
+	/* drain write buffer */
+	mb();
 }
 
 static inline const char *ath10k_pci_get_irq_method(struct ath10k *ar)
-- 
1.9.1