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bnxt_en: Eliminate duplicate barriers on weakly-ordered archs 

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 <okaya@codeaurora.org>
Acked-by: Michael Chan <michael.chan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Sinan Kaya 2018-03-25 10:39:20 -04:00 committed by David S. Miller
parent e42d8cee34
commit fd141fa47c
2 changed files with 10 additions and 1 deletions
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2
drivers/net/ethernet/broadcom/bnxt/bnxt.c
View File

@ -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;

9
drivers/net/ethernet/broadcom/bnxt/bnxt.h
View File

@ -1402,6 +1402,15 @@ 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)
{