From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sinan Kaya Subject: [PATCH v7 6/7] bnxt_en: Eliminate duplicate barriers on weakly-ordered archs Date: Sun, 25 Mar 2018 10:39:20 -0400 Message-ID: <1521988761-30344-7-git-send-email-okaya@codeaurora.org> References: <1521988761-30344-1-git-send-email-okaya@codeaurora.org> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Cc: linux-arm-msm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Sinan Kaya , Michael Chan , linux-kernel@vger.kernel.org To: netdev@vger.kernel.org, timur@codeaurora.org, sulrich@codeaurora.org Return-path: In-Reply-To: <1521988761-30344-1-git-send-email-okaya@codeaurora.org> Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org 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(). Also add mmiowb() so that write code doesn't move outside of scope. Signed-off-by: Sinan Kaya --- drivers/net/ethernet/broadcom/bnxt/bnxt.c | 2 +- drivers/net/ethernet/broadcom/bnxt/bnxt.h | 9 +++++++++ 2 files changed, 10 insertions(+), 1 deletion(-) 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..5e453b9 100644 --- a/drivers/net/ethernet/broadcom/bnxt/bnxt.h +++ b/drivers/net/ethernet/broadcom/bnxt/bnxt.h @@ -1401,6 +1401,15 @@ static inline u32 bnxt_tx_avail(struct bnxt *bp, struct bnxt_tx_ring_info *txr) ((txr->tx_prod - txr->tx_cons) & bp->tx_ring_mask); } +/* For TX and RX ring doorbells with no ordering guarantee*/ +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) { -- 2.7.4