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From: Yannick Vignon <yannick.vignon@oss.nxp.com>
To: Giuseppe Cavallaro <peppe.cavallaro@st.com>,
	Alexandre Torgue <alexandre.torgue@foss.st.com>,
	Jose Abreu <joabreu@synopsys.com>,
	"David S. Miller" <davem@davemloft.net>,
	Jakub Kicinski <kuba@kernel.org>,
	Maxime Coquelin <mcoquelin.stm32@gmail.com>,
	Rayagond Kokatanur <rayagond@vayavyalabs.com>,
	netdev@vger.kernel.org, linux-stm32@st-md-mailman.stormreply.com,
	linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org, sebastien.laveze@oss.nxp.com,
	Vladimir Oltean <olteanv@gmail.com>,
	Xiaoliang Yang <xiaoliang.yang_1@nxp.com>,
	mingkai.hu@nxp.com, Joakim Zhang <qiangqing.zhang@nxp.com>
Cc: Yannick Vignon <yannick.vignon@nxp.com>
Subject: [PATCH net] net: stmmac: ensure PTP time register reads are consistent
Date: Thu,  3 Feb 2022 17:00:25 +0100	[thread overview]
Message-ID: <20220203160025.750632-1-yannick.vignon@oss.nxp.com> (raw)

From: Yannick Vignon <yannick.vignon@nxp.com>

Even if protected from preemption and interrupts, a small time window
remains when the 2 register reads could return inconsistent values,
each time the "seconds" register changes. This could lead to an about
1-second error in the reported time.

Add logic to ensure the "seconds" and "nanoseconds" values are consistent.

Fixes: 92ba6888510c ("stmmac: add the support for PTP hw clock driver")
Signed-off-by: Yannick Vignon <yannick.vignon@nxp.com>
---
 .../ethernet/stmicro/stmmac/stmmac_hwtstamp.c | 19 ++++++++++++-------
 1 file changed, 12 insertions(+), 7 deletions(-)

diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_hwtstamp.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_hwtstamp.c
index 074e2cdfb0fa..a7ec9f4d46ce 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_hwtstamp.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_hwtstamp.c
@@ -145,15 +145,20 @@ static int adjust_systime(void __iomem *ioaddr, u32 sec, u32 nsec,
 
 static void get_systime(void __iomem *ioaddr, u64 *systime)
 {
-	u64 ns;
-
-	/* Get the TSSS value */
-	ns = readl(ioaddr + PTP_STNSR);
-	/* Get the TSS and convert sec time value to nanosecond */
-	ns += readl(ioaddr + PTP_STSR) * 1000000000ULL;
+	u64 ns, sec0, sec1;
+
+	/* Get the TSS value */
+	sec1 = readl_relaxed(ioaddr + PTP_STSR);
+	do {
+		sec0 = sec1;
+		/* Get the TSSS value */
+		ns = readl_relaxed(ioaddr + PTP_STNSR);
+		/* Get the TSS value */
+		sec1 = readl_relaxed(ioaddr + PTP_STSR);
+	} while (sec0 != sec1);
 
 	if (systime)
-		*systime = ns;
+		*systime = ns + (sec1 * 1000000000ULL);
 }
 
 static void get_ptptime(void __iomem *ptpaddr, u64 *ptp_time)
-- 
2.25.1


WARNING: multiple messages have this Message-ID (diff)
From: Yannick Vignon <yannick.vignon@oss.nxp.com>
To: Giuseppe Cavallaro <peppe.cavallaro@st.com>,
	Alexandre Torgue <alexandre.torgue@foss.st.com>,
	Jose Abreu <joabreu@synopsys.com>,
	"David S. Miller" <davem@davemloft.net>,
	Jakub Kicinski <kuba@kernel.org>,
	Maxime Coquelin <mcoquelin.stm32@gmail.com>,
	Rayagond Kokatanur <rayagond@vayavyalabs.com>,
	netdev@vger.kernel.org, linux-stm32@st-md-mailman.stormreply.com,
	linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org, sebastien.laveze@oss.nxp.com,
	Vladimir Oltean <olteanv@gmail.com>,
	Xiaoliang Yang <xiaoliang.yang_1@nxp.com>,
	mingkai.hu@nxp.com, Joakim Zhang <qiangqing.zhang@nxp.com>
Cc: Yannick Vignon <yannick.vignon@nxp.com>
Subject: [PATCH net] net: stmmac: ensure PTP time register reads are consistent
Date: Thu,  3 Feb 2022 17:00:25 +0100	[thread overview]
Message-ID: <20220203160025.750632-1-yannick.vignon@oss.nxp.com> (raw)

From: Yannick Vignon <yannick.vignon@nxp.com>

Even if protected from preemption and interrupts, a small time window
remains when the 2 register reads could return inconsistent values,
each time the "seconds" register changes. This could lead to an about
1-second error in the reported time.

Add logic to ensure the "seconds" and "nanoseconds" values are consistent.

Fixes: 92ba6888510c ("stmmac: add the support for PTP hw clock driver")
Signed-off-by: Yannick Vignon <yannick.vignon@nxp.com>
---
 .../ethernet/stmicro/stmmac/stmmac_hwtstamp.c | 19 ++++++++++++-------
 1 file changed, 12 insertions(+), 7 deletions(-)

diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_hwtstamp.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_hwtstamp.c
index 074e2cdfb0fa..a7ec9f4d46ce 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_hwtstamp.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_hwtstamp.c
@@ -145,15 +145,20 @@ static int adjust_systime(void __iomem *ioaddr, u32 sec, u32 nsec,
 
 static void get_systime(void __iomem *ioaddr, u64 *systime)
 {
-	u64 ns;
-
-	/* Get the TSSS value */
-	ns = readl(ioaddr + PTP_STNSR);
-	/* Get the TSS and convert sec time value to nanosecond */
-	ns += readl(ioaddr + PTP_STSR) * 1000000000ULL;
+	u64 ns, sec0, sec1;
+
+	/* Get the TSS value */
+	sec1 = readl_relaxed(ioaddr + PTP_STSR);
+	do {
+		sec0 = sec1;
+		/* Get the TSSS value */
+		ns = readl_relaxed(ioaddr + PTP_STNSR);
+		/* Get the TSS value */
+		sec1 = readl_relaxed(ioaddr + PTP_STSR);
+	} while (sec0 != sec1);
 
 	if (systime)
-		*systime = ns;
+		*systime = ns + (sec1 * 1000000000ULL);
 }
 
 static void get_ptptime(void __iomem *ptpaddr, u64 *ptp_time)
-- 
2.25.1


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             reply	other threads:[~2022-02-03 16:20 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-02-03 16:00 Yannick Vignon [this message]
2022-02-03 16:00 ` [PATCH net] net: stmmac: ensure PTP time register reads are consistent Yannick Vignon
2022-02-03 16:28 ` Russell King (Oracle)
2022-02-03 16:28   ` Russell King (Oracle)
2022-02-03 16:38   ` Yannick Vignon
2022-02-03 16:38     ` Yannick Vignon
2022-02-03 16:44     ` Russell King (Oracle)
2022-02-03 16:44       ` Russell King (Oracle)
2022-02-03 22:10 ` patchwork-bot+netdevbpf
2022-02-03 22:10   ` patchwork-bot+netdevbpf

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