netdev - [net-next,v2,1/1] net: stmmac: Add dma_wmb() barrier before setting OWN bit in set_rx

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Message-Id: <20240821060307.46350-1-ende.tan@starfivetech.com>
Date: Wed, 21 Aug 2024 14:03:07 +0800
From: ende.tan@...rfivetech.com
To: netdev@...r.kernel.org
Cc: andrew@...n.ch,
	alexandre.torgue@...s.st.com,
	joabreu@...opsys.com,
	davem@...emloft.net,
	edumazet@...gle.com,
	kuba@...nel.org,
	pabeni@...hat.com,
	mcoquelin.stm32@...il.com,
	linux-kernel@...r.kernel.org,
	linux-stm32@...md-mailman.stormreply.com,
	linux-arm-kernel@...ts.infradead.org,
	leyfoon.tan@...rfivetech.com,
	minda.chen@...rfivetech.com,
	endeneer@...il.com,
	Tan En De <ende.tan@...rfivetech.com>
Subject: [net-next,v2,1/1] net: stmmac: Add dma_wmb() barrier before setting OWN bit in set_rx_owner()

From: Tan En De <ende.tan@...rfivetech.com>

Currently, some set_rx_owner() callbacks set interrupt-on-completion bit
in addition to OWN bit, without inserting a dma_wmb() barrier in
between. This might cause missed interrupt if the DMA sees the OWN bit
before the interrupt-on-completion bit is set.

Thus, this patch adds dma_wmb() barrier right before setting OWN bit in
each of the callbacks. Now that the responsibility of calling dma_wmb()
is delegated to the callbacks, let's simplify main driver code by
removing dma_wmb() before stmmac_set_rx_owner().

Signed-off-by: Tan En De <ende.tan@...rfivetech.com>
---
v2:
- Avoid introducing a new function just to set the interrupt-on-completion
  bit, as it is wasteful to do so.
- Delegate the responsibility of calling dma_wmb() from main driver code
  to set_rx_owner() callbacks (i.e. let callbacks to manage the low-level
  ordering/barrier rather than cluttering up the main driver code).
v1:
- https://patchwork.kernel.org/project/netdevbpf/patch/20240814092438.3129-1-ende.tan@starfivetech.com/
---
 drivers/net/ethernet/stmicro/stmmac/dwmac4_descs.c   | 5 ++++-
 drivers/net/ethernet/stmicro/stmmac/dwxgmac2_descs.c | 5 +++--
 drivers/net/ethernet/stmicro/stmmac/enh_desc.c       | 1 +
 drivers/net/ethernet/stmicro/stmmac/norm_desc.c      | 1 +
 drivers/net/ethernet/stmicro/stmmac/stmmac_main.c    | 2 --
 5 files changed, 9 insertions(+), 5 deletions(-)

diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac4_descs.c b/drivers/net/ethernet/stmicro/stmmac/dwmac4_descs.c
index 1c5802e0d7f4..95aea6ad485b 100644
--- a/drivers/net/ethernet/stmicro/stmmac/dwmac4_descs.c
+++ b/drivers/net/ethernet/stmicro/stmmac/dwmac4_descs.c
@@ -186,10 +186,13 @@ static void dwmac4_set_tx_owner(struct dma_desc *p)
 
 static void dwmac4_set_rx_owner(struct dma_desc *p, int disable_rx_ic)
 {
-	p->des3 |= cpu_to_le32(RDES3_OWN | RDES3_BUFFER1_VALID_ADDR);
+	p->des3 |= cpu_to_le32(RDES3_BUFFER1_VALID_ADDR);
 
 	if (!disable_rx_ic)
 		p->des3 |= cpu_to_le32(RDES3_INT_ON_COMPLETION_EN);
+
+	dma_wmb();
+	p->des3 |= cpu_to_le32(RDES3_OWN);
 }
 
 static int dwmac4_get_tx_ls(struct dma_desc *p)
diff --git a/drivers/net/ethernet/stmicro/stmmac/dwxgmac2_descs.c b/drivers/net/ethernet/stmicro/stmmac/dwxgmac2_descs.c
index fc82862a612c..d76ae833c840 100644
--- a/drivers/net/ethernet/stmicro/stmmac/dwxgmac2_descs.c
+++ b/drivers/net/ethernet/stmicro/stmmac/dwxgmac2_descs.c
@@ -56,10 +56,11 @@ static void dwxgmac2_set_tx_owner(struct dma_desc *p)
 
 static void dwxgmac2_set_rx_owner(struct dma_desc *p, int disable_rx_ic)
 {
-	p->des3 |= cpu_to_le32(XGMAC_RDES3_OWN);
-
 	if (!disable_rx_ic)
 		p->des3 |= cpu_to_le32(XGMAC_RDES3_IOC);
+
+	dma_wmb();
+	p->des3 |= cpu_to_le32(XGMAC_RDES3_OWN);
 }
 
 static int dwxgmac2_get_tx_ls(struct dma_desc *p)
diff --git a/drivers/net/ethernet/stmicro/stmmac/enh_desc.c b/drivers/net/ethernet/stmicro/stmmac/enh_desc.c
index 937b7a0466fc..9219fe69ea44 100644
--- a/drivers/net/ethernet/stmicro/stmmac/enh_desc.c
+++ b/drivers/net/ethernet/stmicro/stmmac/enh_desc.c
@@ -289,6 +289,7 @@ static void enh_desc_set_tx_owner(struct dma_desc *p)
 
 static void enh_desc_set_rx_owner(struct dma_desc *p, int disable_rx_ic)
 {
+	dma_wmb();
 	p->des0 |= cpu_to_le32(RDES0_OWN);
 }
 
diff --git a/drivers/net/ethernet/stmicro/stmmac/norm_desc.c b/drivers/net/ethernet/stmicro/stmmac/norm_desc.c
index 68a7cfcb1d8f..d0b703a3346f 100644
--- a/drivers/net/ethernet/stmicro/stmmac/norm_desc.c
+++ b/drivers/net/ethernet/stmicro/stmmac/norm_desc.c
@@ -155,6 +155,7 @@ static void ndesc_set_tx_owner(struct dma_desc *p)
 
 static void ndesc_set_rx_owner(struct dma_desc *p, int disable_rx_ic)
 {
+	dma_wmb();
 	p->des0 |= cpu_to_le32(RDES0_OWN);
 }
 
diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
index d9fca8d1227c..859a2c4c9e5c 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
@@ -4848,7 +4848,6 @@ static inline void stmmac_rx_refill(struct stmmac_priv *priv, u32 queue)
 		if (!priv->use_riwt)
 			use_rx_wd = false;
 
-		dma_wmb();
 		stmmac_set_rx_owner(priv, p, use_rx_wd);
 
 		entry = STMMAC_GET_ENTRY(entry, priv->dma_conf.dma_rx_size);
@@ -5205,7 +5204,6 @@ static bool stmmac_rx_refill_zc(struct stmmac_priv *priv, u32 queue, u32 budget)
 		if (!priv->use_riwt)
 			use_rx_wd = false;
 
-		dma_wmb();
 		stmmac_set_rx_owner(priv, rx_desc, use_rx_wd);
 
 		entry = STMMAC_GET_ENTRY(entry, priv->dma_conf.dma_rx_size);
-- 
2.34.1