Re: [net v1] net: stmmac: fixed new system time seconds value calculation
From: David Miller
Date:  Sat Jun 22 2019 - 19:18:36 EST
From: Voon Weifeng <weifeng.voon@xxxxxxxxx>
Date: Wed, 19 Jun 2019 22:13:48 +0800
> From: Roland Hii <roland.king.guan.hii@xxxxxxxxx>
> 
> When ADDSUB bit is set, the system time seconds field is calculated as
> the complement of the seconds part of the update value.
> 
> For example, if 3.000000001 seconds need to be subtracted from the
> system time, this field is calculated as
> 2^32 - 3 = 4294967296 - 3 = 0x100000000 - 3 = 0xFFFFFFFD
> 
> Previously, the 0x100000000 is mistakenly written as 100000000.
> 
> This is further simplified from
>   sec = (0x100000000ULL - sec);
> to
>   sec = -sec;
> 
> Fixes: ba1ffd74df74 ("stmmac: fix PTP support for GMAC4")
> Signed-off-by: Roland Hii <roland.king.guan.hii@xxxxxxxxx>
> Signed-off-by: Ong Boon Leong <boon.leong.ong@xxxxxxxxx>
> Signed-off-by: Voon Weifeng <weifeng.voon@xxxxxxxxx>
Applied and queued up for -stable.