Messages in this thread | | | Date | Sun, 25 Mar 2018 09:33:35 -0400 | From | okaya@codeauro ... | Subject | Re: [PATCH v4 17/17] net: ena: Eliminate duplicate barriers on weakly-ordered archs |
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On 2018-03-25 08:06, Belgazal, Netanel wrote: > I think you should either add a parameter to > ena_com_write_sq_doorbell() or add ena_com_write_sq_doorbell_rel(). > Right now, you have unused function.
That is true. I got rid of ena_com_write_sq_doorbell_rel.
> > On 3/20/18, 4:43 AM, "Sinan Kaya" <okaya@codeaurora.org> wrote: > > Code includes barrier() 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 barrier(). > > Since code already has an explicit barrier call, changing writel() > to > writel_relaxed(). > > Signed-off-by: Sinan Kaya <okaya@codeaurora.org> > --- > drivers/net/ethernet/amazon/ena/ena_com.c | 6 ++++-- > drivers/net/ethernet/amazon/ena/ena_eth_com.h | 22 > ++++++++++++++++++++-- > drivers/net/ethernet/amazon/ena/ena_netdev.c | 4 ++-- > 3 files changed, 26 insertions(+), 6 deletions(-) > > diff --git a/drivers/net/ethernet/amazon/ena/ena_com.c > b/drivers/net/ethernet/amazon/ena/ena_com.c > index bf2de52..b6e628f 100644 > --- a/drivers/net/ethernet/amazon/ena/ena_com.c > +++ b/drivers/net/ethernet/amazon/ena/ena_com.c > @@ -631,7 +631,8 @@ static u32 ena_com_reg_bar_read32(struct > ena_com_dev *ena_dev, u16 offset) > */ > wmb(); > > - writel(mmio_read_reg, ena_dev->reg_bar + > ENA_REGS_MMIO_REG_READ_OFF); > + writel_relaxed(mmio_read_reg, > + ena_dev->reg_bar + ENA_REGS_MMIO_REG_READ_OFF); > > for (i = 0; i < timeout; i++) { > if (read_resp->req_id == mmio_read->seq_num) > @@ -1826,7 +1827,8 @@ void ena_com_aenq_intr_handler(struct > ena_com_dev *dev, void *data) > > /* write the aenq doorbell after all AENQ descriptors were read > */ > mb(); > - writel((u32)aenq->head, dev->reg_bar + > ENA_REGS_AENQ_HEAD_DB_OFF); > + writel_relaxed((u32)aenq->head, > + dev->reg_bar + ENA_REGS_AENQ_HEAD_DB_OFF); > } > > int ena_com_dev_reset(struct ena_com_dev *ena_dev, > diff --git a/drivers/net/ethernet/amazon/ena/ena_eth_com.h > b/drivers/net/ethernet/amazon/ena/ena_eth_com.h > index 2f76572..09ef7cd 100644 > --- a/drivers/net/ethernet/amazon/ena/ena_eth_com.h > +++ b/drivers/net/ethernet/amazon/ena/ena_eth_com.h > @@ -107,7 +107,8 @@ static inline int > ena_com_sq_empty_space(struct ena_com_io_sq *io_sq) > return io_sq->q_depth - 1 - cnt; > } > > -static inline int ena_com_write_sq_doorbell(struct ena_com_io_sq > *io_sq) > +static inline int ena_com_write_sq_doorbell(struct ena_com_io_sq > *io_sq, > + bool relaxed) > { > u16 tail; > > @@ -116,7 +117,24 @@ static inline int > ena_com_write_sq_doorbell(struct ena_com_io_sq *io_sq) > pr_debug("write submission queue doorbell for queue: %d tail: > %d\n", > io_sq->qid, tail); > > - writel(tail, io_sq->db_addr); > + if (relaxed) > + writel_relaxed(tail, io_sq->db_addr); > + else > + writel(tail, io_sq->db_addr); > + > + return 0; > +} > + > +static inline int ena_com_write_sq_doorbell_rel(struct > ena_com_io_sq *io_sq) > +{ > + u16 tail; > + > + tail = io_sq->tail; > + > + pr_debug("write submission queue doorbell for queue: %d tail: > %d\n", > + io_sq->qid, tail); > + > + writel_relaxed(tail, io_sq->db_addr); > > return 0; > } > diff --git a/drivers/net/ethernet/amazon/ena/ena_netdev.c > b/drivers/net/ethernet/amazon/ena/ena_netdev.c > index 6975150..0530201 100644 > --- a/drivers/net/ethernet/amazon/ena/ena_netdev.c > +++ b/drivers/net/ethernet/amazon/ena/ena_netdev.c > @@ -556,7 +556,7 @@ static int ena_refill_rx_bufs(struct ena_ring > *rx_ring, u32 num) > * issue a doorbell > */ > wmb(); > - ena_com_write_sq_doorbell(rx_ring->ena_com_io_sq); > + ena_com_write_sq_doorbell(rx_ring->ena_com_io_sq, true); > } > > rx_ring->next_to_use = next_to_use; > @@ -2151,7 +2151,7 @@ static netdev_tx_t ena_start_xmit(struct > sk_buff *skb, struct net_device *dev) > > if (netif_xmit_stopped(txq) || !skb->xmit_more) { > /* trigger the dma engine */ > - ena_com_write_sq_doorbell(tx_ring->ena_com_io_sq); > + ena_com_write_sq_doorbell(tx_ring->ena_com_io_sq, false); > u64_stats_update_begin(&tx_ring->syncp); > tx_ring->tx_stats.doorbells++; > u64_stats_update_end(&tx_ring->syncp); > -- > 2.7.4
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