Thread (28 messages) 28 messages, 4 authors, 2018-03-16

[PATCH 1/7] i40e/i40evf: Eliminate duplicate barriers on weakly-ordered archs

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STALE3137d

From: Sinan Kaya <hidden>
Date: 2018-03-14 03:20:39
Also in: intel-wired-lan, linux-arm-kernel, linux-arm-msm, lkml
Subsystem: intel ethernet drivers, networking drivers, the rest · Maintainers: Tony Nguyen, Przemek Kitszel, Andrew Lunn, "David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Linus Torvalds

Code includes wmb() followed by writel(). writel() already has a barrier
on some architectures like arm64.

This ends up CPU observing two barriers back to back before executing the
register write.

Since code already has an explicit barrier call, changing writel() to
writel_relaxed().

Signed-off-by: Sinan Kaya <redacted>
---
 drivers/net/ethernet/intel/i40e/i40e_txrx.c   | 2 +-
 drivers/net/ethernet/intel/i40evf/i40e_txrx.c | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/net/ethernet/intel/i40e/i40e_txrx.c b/drivers/net/ethernet/intel/i40e/i40e_txrx.c
index e554aa6cf..7028516 100644
--- a/drivers/net/ethernet/intel/i40e/i40e_txrx.c
+++ b/drivers/net/ethernet/intel/i40e/i40e_txrx.c
@@ -1375,7 +1375,7 @@ static inline void i40e_release_rx_desc(struct i40e_ring *rx_ring, u32 val)
 	 * such as IA-64).
 	 */
 	wmb();
-	writel(val, rx_ring->tail);
+	writel_relaxed(val, rx_ring->tail);
 }
 
 /**
diff --git a/drivers/net/ethernet/intel/i40evf/i40e_txrx.c b/drivers/net/ethernet/intel/i40evf/i40e_txrx.c
index 357d605..2d323fc 100644
--- a/drivers/net/ethernet/intel/i40evf/i40e_txrx.c
+++ b/drivers/net/ethernet/intel/i40evf/i40e_txrx.c
@@ -667,7 +667,7 @@ static inline void i40e_release_rx_desc(struct i40e_ring *rx_ring, u32 val)
 	 * such as IA-64).
 	 */
 	wmb();
-	writel(val, rx_ring->tail);
+	writel_relaxed(val, rx_ring->tail);
 }
 
 /**
-- 
2.7.4
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