From: Yannick Vignon <yannick.vignon@xxxxxxx>
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 <yannick.vignon@xxxxxxx>
Reviewed-by: Russell King (Oracle) <rmk+kernel@xxxxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20220203160025.750632-1-yannick.vignon@xxxxxxxxxxx
Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/net/ethernet/stmicro/stmmac/stmmac_hwtstamp.c | 17 +++++++++++------
1 file changed, 11 insertions(+), 6 deletions(-)
--- 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 *
static void get_systime(void __iomem *ioaddr, u64 *systime)
{
- u64 ns;
+ u64 ns, sec0, sec1;
- /* 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;
+ /* 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 = {
