[PATCH 4.9 21/56] net: stmmac: Fix TX timestamp calculation

Greg Kroah-Hartman
2018-03-02T08:51:07Z

From: Fredrik Hallenberg <megahallon@gmail.com>

[ Upstream commit 200922c93f008e03ddc804c6dacdf26ca1ba86d7 ]

When using GMAC4 the value written in PTP_SSIR should be shifted however
the shifted value is also used in subsequent calculations which results
in a bad timestamp value.

Signed-off-by: Fredrik Hallenberg <megahallon@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/net/ethernet/stmicro/stmmac/stmmac_hwtstamp.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)

--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_hwtstamp.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_hwtstamp.c
@@ -38,6 +38,7 @@ static u32 stmmac_config_sub_second_incr
{
u32 value = readl(ioaddr + PTP_TCR);
unsigned long data;
+ u32 reg_value;

/* For GMAC3.x, 4.x versions, convert the ptp_clock to nano second
* formula = (1/ptp_clock) * 1000000000
@@ -54,10 +55,11 @@ static u32 stmmac_config_sub_second_incr

data &= PTP_SSIR_SSINC_MASK;

+ reg_value = data;
if (gmac4)
- data = data << GMAC4_PTP_SSIR_SSINC_SHIFT;
+ reg_value <<= GMAC4_PTP_SSIR_SSINC_SHIFT;

- writel(data, ioaddr + PTP_SSIR);
+ writel(reg_value, ioaddr + PTP_SSIR);

return data;
}