From 00b4070cf444d7e36177ac0cad82318bdb268a14 Mon Sep 17 00:00:00 2001 From: Yannick Vignon Date: Thu, 3 Feb 2022 17:00:25 +0100 Subject: net: stmmac: ensure PTP time register reads are consistent commit 80d4609008e6d696a279e39ae7458c916fcd44c1 upstream. 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 Reviewed-by: Russell King (Oracle) Link: https://lore.kernel.org/r/20220203160025.750632-1-yannick.vignon@oss.nxp.com Signed-off-by: Jakub Kicinski Signed-off-by: Greg Kroah-Hartman --- drivers/net/ethernet/stmicro/stmmac/stmmac_hwtstamp.c | 19 ++++++++++++------- 1 file changed, 12 insertions(+), 7 deletions(-) (limited to 'drivers/net') diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_hwtstamp.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_hwtstamp.c index e1fbd7c81bfa..08a058e1bc75 100644 --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_hwtstamp.c +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_hwtstamp.c @@ -159,15 +159,20 @@ 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); } const struct stmmac_hwtimestamp stmmac_ptp = { -- cgit v1.2.3