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

Re: [PATCH 4/7] igbvf: eliminate duplicate barriers on weakly-ordered archs

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From: Alexander Duyck <hidden>
Date: 2018-03-15 01:48:45
Also in: intel-wired-lan, linux-arm-kernel, linux-arm-msm, lkml

On Tue, Mar 13, 2018 at 8:20 PM, Sinan Kaya [off-list ref] wrote:
quoted hunk ↗ jump to hunk
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/igbvf/netdev.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/net/ethernet/intel/igbvf/netdev.c b/drivers/net/ethernet/intel/igbvf/netdev.c
index 4214c15..fe3441b 100644
--- a/drivers/net/ethernet/intel/igbvf/netdev.c
+++ b/drivers/net/ethernet/intel/igbvf/netdev.c
@@ -251,7 +251,7 @@ static void igbvf_alloc_rx_buffers(struct igbvf_ring *rx_ring,
                 * such as IA-64).
                */
                wmb();
-               writel(i, adapter->hw.hw_addr + rx_ring->tail);
+               writel_relaxed(i, adapter->hw.hw_addr + rx_ring->tail);
        }
 }
This one missed the writel at the end of igbvf_tx_queue_adv().
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