[PATCH v4 15/17] bnxt_en: Eliminate duplicate barriers on weakly-ordered archs
From: Sinan Kaya <hidden>
Date: 2018-03-20 02:44:27
Also in:
linux-arm-kernel, linux-arm-msm, lkml
Subsystem:
broadcom bnxt_en 50 gigabit ethernet driver, networking drivers, the rest · Maintainers:
Michael Chan, Pavan Chebbi, 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. Create a new wrapper function with relaxed write operator. Use the new wrapper when a write is following a wmb(). Since code already has an explicit barrier call, changing writel() to writel_relaxed(). Signed-off-by: Sinan Kaya <redacted> --- drivers/net/ethernet/broadcom/bnxt/bnxt.c | 2 +- drivers/net/ethernet/broadcom/bnxt/bnxt.h | 11 ++++++++++- drivers/net/ethernet/broadcom/bnxt/bnxt_ethtool.c | 2 +- 3 files changed, 12 insertions(+), 3 deletions(-)
diff --git a/drivers/net/ethernet/broadcom/bnxt/bnxt.c b/drivers/net/ethernet/broadcom/bnxt/bnxt.c
index 1500243..befb538 100644
--- a/drivers/net/ethernet/broadcom/bnxt/bnxt.c
+++ b/drivers/net/ethernet/broadcom/bnxt/bnxt.c@@ -1922,7 +1922,7 @@ static int bnxt_poll_work(struct bnxt *bp, struct bnxt_napi *bnapi, int budget) /* Sync BD data before updating doorbell */ wmb(); - bnxt_db_write(bp, db, DB_KEY_TX | prod); + bnxt_db_write_relaxed(bp, db, DB_KEY_TX | prod); } cpr->cp_raw_cons = raw_cons;
diff --git a/drivers/net/ethernet/broadcom/bnxt/bnxt.h b/drivers/net/ethernet/broadcom/bnxt/bnxt.h
index 1989c47..4c0d048 100644
--- a/drivers/net/ethernet/broadcom/bnxt/bnxt.h
+++ b/drivers/net/ethernet/broadcom/bnxt/bnxt.h@@ -1402,11 +1402,20 @@ static inline u32 bnxt_tx_avail(struct bnxt *bp, struct bnxt_tx_ring_info *txr) } /* For TX and RX ring doorbells */ +static inline void bnxt_db_write_relaxed(struct bnxt *bp, void __iomem *db, + u32 val) +{ + writel_relaxed(val, db); + if (bp->flags & BNXT_FLAG_DOUBLE_DB) + writel_relaxed(val, db); +} + +/* For TX and RX ring doorbells */ static inline void bnxt_db_write(struct bnxt *bp, void __iomem *db, u32 val) { writel(val, db); if (bp->flags & BNXT_FLAG_DOUBLE_DB) - writel(val, db); + writel_relaxed(val, db); } extern const u16 bnxt_lhint_arr[];
diff --git a/drivers/net/ethernet/broadcom/bnxt/bnxt_ethtool.c b/drivers/net/ethernet/broadcom/bnxt/bnxt_ethtool.c
index 1801582..a1b1060 100644
--- a/drivers/net/ethernet/broadcom/bnxt/bnxt_ethtool.c
+++ b/drivers/net/ethernet/broadcom/bnxt/bnxt_ethtool.c@@ -2403,7 +2403,7 @@ static int bnxt_run_loopback(struct bnxt *bp) /* Sync BD data before updating doorbell */ wmb(); - bnxt_db_write(bp, txr->tx_doorbell, DB_KEY_TX | txr->tx_prod); + bnxt_db_write_relaxed(bp, txr->tx_doorbell, DB_KEY_TX | txr->tx_prod); rc = bnxt_poll_loopback(bp, pkt_size); dma_unmap_single(&bp->pdev->dev, map, pkt_size, PCI_DMA_TODEVICE);
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2.7.4