lkml.org 
[lkml]   [2018]   [Mar]   [16]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH v3 13/18] net: cxgb4/cxgb4vf: Eliminate duplicate barriers on weakly-ordered archs
Date
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().

Signed-off-by: Sinan Kaya <okaya@codeaurora.org>
---
drivers/net/ethernet/chelsio/cxgb4/cxgb4.h | 6 ++++++
drivers/net/ethernet/chelsio/cxgb4/cxgb4_main.c | 13 +++++++------
drivers/net/ethernet/chelsio/cxgb4/sge.c | 8 ++++----
drivers/net/ethernet/chelsio/cxgb4/t4_hw.c | 2 +-
drivers/net/ethernet/chelsio/cxgb4vf/adapter.h | 14 ++++++++++++++
drivers/net/ethernet/chelsio/cxgb4vf/sge.c | 16 +++++++++-------
6 files changed, 41 insertions(+), 18 deletions(-)

diff --git a/drivers/net/ethernet/chelsio/cxgb4/cxgb4.h b/drivers/net/ethernet/chelsio/cxgb4/cxgb4.h
index 9040e13..6bde0b9 100644
--- a/drivers/net/ethernet/chelsio/cxgb4/cxgb4.h
+++ b/drivers/net/ethernet/chelsio/cxgb4/cxgb4.h
@@ -1202,6 +1202,12 @@ static inline void t4_write_reg(struct adapter *adap, u32 reg_addr, u32 val)
writel(val, adap->regs + reg_addr);
}

+static inline void t4_write_reg_relaxed(struct adapter *adap, u32 reg_addr,
+ u32 val)
+{
+ writel_relaxed(val, adap->regs + reg_addr);
+}
+
#ifndef readq
static inline u64 readq(const volatile void __iomem *addr)
{
diff --git a/drivers/net/ethernet/chelsio/cxgb4/cxgb4_main.c b/drivers/net/ethernet/chelsio/cxgb4/cxgb4_main.c
index 7b452e8..276472d 100644
--- a/drivers/net/ethernet/chelsio/cxgb4/cxgb4_main.c
+++ b/drivers/net/ethernet/chelsio/cxgb4/cxgb4_main.c
@@ -1723,8 +1723,8 @@ int cxgb4_sync_txq_pidx(struct net_device *dev, u16 qid, u16 pidx,
else
val = PIDX_T5_V(delta);
wmb();
- t4_write_reg(adap, MYPF_REG(SGE_PF_KDOORBELL_A),
- QID_V(qid) | val);
+ t4_write_reg_relaxed(adap, MYPF_REG(SGE_PF_KDOORBELL_A),
+ QID_V(qid) | val);
}
out:
return ret;
@@ -1902,8 +1902,9 @@ static void enable_txq_db(struct adapter *adap, struct sge_txq *q)
* are committed before we tell HW about them.
*/
wmb();
- t4_write_reg(adap, MYPF_REG(SGE_PF_KDOORBELL_A),
- QID_V(q->cntxt_id) | PIDX_V(q->db_pidx_inc));
+ t4_write_reg_relaxed(adap, MYPF_REG(SGE_PF_KDOORBELL_A),
+ QID_V(q->cntxt_id) |
+ PIDX_V(q->db_pidx_inc));
q->db_pidx_inc = 0;
}
q->db_disabled = 0;
@@ -2003,8 +2004,8 @@ static void sync_txq_pidx(struct adapter *adap, struct sge_txq *q)
else
val = PIDX_T5_V(delta);
wmb();
- t4_write_reg(adap, MYPF_REG(SGE_PF_KDOORBELL_A),
- QID_V(q->cntxt_id) | val);
+ t4_write_reg_relaxed(adap, MYPF_REG(SGE_PF_KDOORBELL_A),
+ QID_V(q->cntxt_id) | val);
}
out:
q->db_disabled = 0;
diff --git a/drivers/net/ethernet/chelsio/cxgb4/sge.c b/drivers/net/ethernet/chelsio/cxgb4/sge.c
index 6e310a0..1a1738a 100644
--- a/drivers/net/ethernet/chelsio/cxgb4/sge.c
+++ b/drivers/net/ethernet/chelsio/cxgb4/sge.c
@@ -530,11 +530,11 @@ static inline void ring_fl_db(struct adapter *adap, struct sge_fl *q)
* mechanism.
*/
if (unlikely(q->bar2_addr == NULL)) {
- t4_write_reg(adap, MYPF_REG(SGE_PF_KDOORBELL_A),
- val | QID_V(q->cntxt_id));
+ t4_write_reg_relaxed(adap, MYPF_REG(SGE_PF_KDOORBELL_A),
+ val | QID_V(q->cntxt_id));
} else {
- writel(val | QID_V(q->bar2_qid),
- q->bar2_addr + SGE_UDB_KDOORBELL);
+ writel_relaxed(val | QID_V(q->bar2_qid),
+ q->bar2_addr + SGE_UDB_KDOORBELL);

/* This Write memory Barrier will force the write to
* the User Doorbell area to be flushed.
diff --git a/drivers/net/ethernet/chelsio/cxgb4/t4_hw.c b/drivers/net/ethernet/chelsio/cxgb4/t4_hw.c
index 920bccd..8b723a0 100644
--- a/drivers/net/ethernet/chelsio/cxgb4/t4_hw.c
+++ b/drivers/net/ethernet/chelsio/cxgb4/t4_hw.c
@@ -139,7 +139,7 @@ void t4_write_indirect(struct adapter *adap, unsigned int addr_reg,
{
while (nregs--) {
t4_write_reg(adap, addr_reg, start_idx++);
- t4_write_reg(adap, data_reg, *vals++);
+ t4_write_reg_relaxed(adap, data_reg, *vals++);
}
}

diff --git a/drivers/net/ethernet/chelsio/cxgb4vf/adapter.h b/drivers/net/ethernet/chelsio/cxgb4vf/adapter.h
index 5883f09..00247be4 100644
--- a/drivers/net/ethernet/chelsio/cxgb4vf/adapter.h
+++ b/drivers/net/ethernet/chelsio/cxgb4vf/adapter.h
@@ -442,6 +442,20 @@ static inline void t4_write_reg(struct adapter *adapter, u32 reg_addr, u32 val)
writel(val, adapter->regs + reg_addr);
}

+/**
+ * t4_write_reg_relaxed - write a HW register without ordering guarantees
+ * @adapter: the adapter
+ * @reg_addr: the register address
+ * @val: the value to write
+ *
+ * Write a 32-bit value into the given HW register.
+ */
+static inline void t4_write_reg_relaxed(struct adapter *adapter, u32 reg_addr,
+ u32 val)
+{
+ writel_relaxed(val, adapter->regs + reg_addr);
+}
+
#ifndef readq
static inline u64 readq(const volatile void __iomem *addr)
{
diff --git a/drivers/net/ethernet/chelsio/cxgb4vf/sge.c b/drivers/net/ethernet/chelsio/cxgb4vf/sge.c
index dfce5df..1d98387 100644
--- a/drivers/net/ethernet/chelsio/cxgb4vf/sge.c
+++ b/drivers/net/ethernet/chelsio/cxgb4vf/sge.c
@@ -546,12 +546,13 @@ static inline void ring_fl_db(struct adapter *adapter, struct sge_fl *fl)
* mechanism.
*/
if (unlikely(fl->bar2_addr == NULL)) {
- t4_write_reg(adapter,
- T4VF_SGE_BASE_ADDR + SGE_VF_KDOORBELL,
- QID_V(fl->cntxt_id) | val);
+ t4_write_reg_relaxed(adapter,
+ T4VF_SGE_BASE_ADDR +
+ SGE_VF_KDOORBELL,
+ QID_V(fl->cntxt_id) | val);
} else {
- writel(val | QID_V(fl->bar2_qid),
- fl->bar2_addr + SGE_UDB_KDOORBELL);
+ writel_relaxed(val | QID_V(fl->bar2_qid),
+ fl->bar2_addr + SGE_UDB_KDOORBELL);

/* This Write memory Barrier will force the write to
* the User Doorbell area to be flushed.
@@ -980,8 +981,9 @@ static inline void ring_tx_db(struct adapter *adapter, struct sge_txq *tq,
if (unlikely(tq->bar2_addr == NULL)) {
u32 val = PIDX_V(n);

- t4_write_reg(adapter, T4VF_SGE_BASE_ADDR + SGE_VF_KDOORBELL,
- QID_V(tq->cntxt_id) | val);
+ t4_write_reg_relaxed(adapter,
+ T4VF_SGE_BASE_ADDR + SGE_VF_KDOORBELL,
+ QID_V(tq->cntxt_id) | val);
} else {
u32 val = PIDX_T5_V(n);

--
2.7.4
\
 
 \ /
  Last update: 2018-03-16 17:22    [W:0.037 / U:10.752 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site