netdev - [PATCH] net: stmmac: fix FPE events losing

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Date: Tue, 14 Nov 2023 11:07:34 +0000
From: Jianheng Zhang <Jianheng.Zhang@...opsys.com>
To: Alexandre Torgue <alexandre.torgue@...s.st.com>,
        Jose Abreu <Jose.Abreu@...opsys.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Tan Tee Min <tee.min.tan@...el.com>,
        Ong Boon Leong <boon.leong.ong@...el.com>,
        Voon Weifeng <weifeng.voon@...el.com>,
        Mohammad Athari Bin Ismail <mohammad.athari.ismail@...el.com>
CC: "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-stm32@...md-mailman.stormreply.com"
	<linux-stm32@...md-mailman.stormreply.com>,
        "linux-arm-kernel@...ts.infradead.org"
	<linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>
Subject: [PATCH] net: stmmac: fix FPE events losing

The 32-bit access of register MAC_FPE_CTRL_STS may clear the FPE status
bits unexpectedly. Use 8-bit access for MAC_FPE_CTRL_STS control bits to
avoid unexpected access of MAC_FPE_CTRL_STS status bits that can reduce
the FPE handshake retries.

The bit[19:17] of register MAC_FPE_CTRL_STS are status register bits.
Those bits are clear on read (or write of 1 when RCWE bit in
MAC_CSR_SW_Ctrl register is set). Using 32-bit access for
MAC_FPE_CTRL_STS control bits makes side effects that clear the status
bits. Then the stmmac interrupt handler missing FPE event status and
leads to FPE handshake failure and retries.

The bit[7:0] of register MAC_FPE_CTRL_STS are control bits or reserved
that have no access side effects, so can use 8-bit access for
MAC_FPE_CTRL_STS control bits.

Fixes: 5a5586112b92 ("net: stmmac: support FPE link partner hand-shaking procedure")
Signed-off-by: jianheng <jianheng@...opsys.com>
---
 drivers/net/ethernet/stmicro/stmmac/dwmac5.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac5.c b/drivers/net/ethernet/stmicro/stmmac/dwmac5.c
index e95d35f..7333995 100644
--- a/drivers/net/ethernet/stmicro/stmmac/dwmac5.c
+++ b/drivers/net/ethernet/stmicro/stmmac/dwmac5.c
@@ -716,11 +716,11 @@ void dwmac5_fpe_configure(void __iomem *ioaddr, u32 num_txq, u32 num_rxq,
 	u32 value;
 
 	if (!enable) {
-		value = readl(ioaddr + MAC_FPE_CTRL_STS);
+		value = readb(ioaddr + MAC_FPE_CTRL_STS);
 
 		value &= ~EFPE;
 
-		writel(value, ioaddr + MAC_FPE_CTRL_STS);
+		writeb(value, ioaddr + MAC_FPE_CTRL_STS);
 		return;
 	}
 
@@ -729,9 +729,9 @@ void dwmac5_fpe_configure(void __iomem *ioaddr, u32 num_txq, u32 num_rxq,
 	value |= (num_rxq - 1) << GMAC_RXQCTRL_FPRQ_SHIFT;
 	writel(value, ioaddr + GMAC_RXQ_CTRL1);
 
-	value = readl(ioaddr + MAC_FPE_CTRL_STS);
+	value = readb(ioaddr + MAC_FPE_CTRL_STS);
 	value |= EFPE;
-	writel(value, ioaddr + MAC_FPE_CTRL_STS);
+	writeb(value, ioaddr + MAC_FPE_CTRL_STS);
 }
 
 int dwmac5_fpe_irq_status(void __iomem *ioaddr, struct net_device *dev)
@@ -770,7 +770,7 @@ void dwmac5_fpe_send_mpacket(void __iomem *ioaddr, enum stmmac_mpacket_type type
 {
 	u32 value;
 
-	value = readl(ioaddr + MAC_FPE_CTRL_STS);
+	value = readb(ioaddr + MAC_FPE_CTRL_STS);
 
 	if (type == MPACKET_VERIFY) {
 		value &= ~SRSP;
@@ -780,5 +780,5 @@ void dwmac5_fpe_send_mpacket(void __iomem *ioaddr, enum stmmac_mpacket_type type
 		value |= SRSP;
 	}
 
-	writel(value, ioaddr + MAC_FPE_CTRL_STS);
+	writeb(value, ioaddr + MAC_FPE_CTRL_STS);
 }
-- 
1.8.3.1