// SPDX-License-Identifier: GPL-2.0+
/* Copyright (C) 2011 Richard Cochran <richardcochran@gmail.com> */
#include <linux/module.h>
#include <linux/device.h>
#include <linux/pci.h>
#include <linux/ptp_classify.h>
#include "igb.h"
#define INCVALUE_MASK 0x7fffffff
#define ISGN 0x80000000
/* The 82580 timesync updates the system timer every 8ns by 8ns,
* and this update value cannot be reprogrammed.
*
* Neither the 82576 nor the 82580 offer registers wide enough to hold
* nanoseconds time values for very long. For the 82580, SYSTIM always
* counts nanoseconds, but the upper 24 bits are not available. The
* frequency is adjusted by changing the 32 bit fractional nanoseconds
* register, TIMINCA.
*
* For the 82576, the SYSTIM register time unit is affect by the
* choice of the 24 bit TININCA:IV (incvalue) field. Five bits of this
* field are needed to provide the nominal 16 nanosecond period,
* leaving 19 bits for fractional nanoseconds.
*
* We scale the NIC clock cycle by a large factor so that relatively
* small clock corrections can be added or subtracted at each clock
* tick. The drawbacks of a large factor are a) that the clock
* register overflows more quickly (not such a big deal) and b) that
* the increment per tick has to fit into 24 bits. As a result we
* need to use a shift of 19 so we can fit a value of 16 into the
* TIMINCA register.
*
*
* SYSTIMH SYSTIML
* +--------------+ +---+---+------+
* 82576 | 32 | | 8 | 5 | 19 |
* +--------------+ +---+---+------+
* \________ 45 bits _______/ fract
*
* +----------+---+ +--------------+
* 82580 | 24 | 8 | | 32 |
* +----------+---+ +--------------+
* reserved \______ 40 bits _____/
*
*
* The 45 bit 82576 SYSTIM overflows every
* 2^45 * 10^-9 / 3600 = 9.77 hours.
*
* The 40 bit 82580 SYSTIM overflows every
* 2^40 * 10^-9 / 60 = 18.3 minutes.
*
* SYSTIM is converted to real time using a timecounter. As
* timecounter_cyc2time() allows old ti
