Merge tag 'v5.7-rc7' into perf/core, to pick up fixes

Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 8 insertions, 4 deletions

diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_hwtstamp.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_hwtstamp.c
index fcf080243a0f..d291612eeafb 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_hwtstamp.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_hwtstamp.c
@@ -27,12 +27,16 @@ static void config_sub_second_increment(void __iomem *ioaddr,
 	unsigned long data;
 	u32 reg_value;
 
-	/* For GMAC3.x, 4.x versions, convert the ptp_clock to nano second
-	 *	formula = (1/ptp_clock) * 1000000000
-	 * where ptp_clock is 50MHz if fine method is used to update system
+	/* For GMAC3.x, 4.x versions, in "fine adjustement mode" set sub-second
+	 * increment to twice the number of nanoseconds of a clock cycle.
+	 * The calculation of the default_addend value by the caller will set it
+	 * to mid-range = 2^31 when the remainder of this division is zero,
+	 * which will make the accumulator overflow once every 2 ptp_clock
+	 * cycles, adding twice the number of nanoseconds of a clock cycle :
+	 * 2000000000ULL / ptp_clock.
 	 */
 	if (value & PTP_TCR_TSCFUPDT)
-		data = (1000000000ULL / 50000000);
+		data = (2000000000ULL / ptp_clock);
 	else
 		data = (1000000000ULL / ptp_clock);