// SPDX-License-Identifier: GPL-2.0
//
// Copyright (c) 2023, 2024 Pengutronix,
//               Marc Kleine-Budde <kernel@pengutronix.de>
//

#include <linux/clocksource.h>

#include "rockchip_canfd.h"

static u64 rkcanfd_timestamp_read(struct cyclecounter *cc)
{
        const struct rkcanfd_priv *priv = container_of(cc, struct rkcanfd_priv, cc);

        return rkcanfd_get_timestamp(priv);
}

void rkcanfd_skb_set_timestamp(const struct rkcanfd_priv *priv,
                               struct sk_buff *skb, const u32 timestamp)
{
        struct skb_shared_hwtstamps *hwtstamps = skb_hwtstamps(skb);
        u64 ns;

        ns = timecounter_cyc2time(&priv->tc, timestamp);

        hwtstamps->hwtstamp = ns_to_ktime(ns);
}

static void rkcanfd_timestamp_work(struct work_struct *work)
{
        const struct delayed_work *delayed_work = to_delayed_work(work);
        struct rkcanfd_priv *priv;

        priv = container_of(delayed_work, struct rkcanfd_priv, timestamp);
        timecounter_read(&priv->tc);

        schedule_delayed_work(&priv->timestamp, priv->work_delay_jiffies);
}

void rkcanfd_timestamp_init(struct rkcanfd_priv *priv)
{
        const struct can_bittiming *dbt = &priv->can.fd.data_bittiming;
        const struct can_bittiming *bt = &priv->can.bittiming;
        struct cyclecounter *cc = &priv->cc;
        u32 bitrate, div, reg, rate;
        u64 work_delay_ns;
        u64 max_cycles;

        /* At the standard clock rate of 300Mhz on the rk3658, the 32
         * bit timer overflows every 14s. This means that we have to
         * poll it quite often to avoid missing a wrap around.
         *
         * Divide it down to a reasonable rate, at least twice the bit
         * rate.
         */
        bitrate = max(bt->bitrate, dbt->bitrate);
        div = min(DIV_ROUND_UP(priv->can.clock.freq, bitrate * 2),
                  FIELD_MAX(RKCANFD_REG_TIMESTAMP_CTRL_TIME_BASE_COUNTER_PRESCALE) + 1);

        reg = FIELD_PREP(RKCANFD_REG_TIMESTAMP_CTRL_TIME_BASE_COUNTER_PRESCALE,
                         div - 1) |
                RKCANFD_REG_TIMESTAMP_CTRL_TIME_BASE_COUNTER_ENABLE;
        rkcanfd_write(priv, RKCANFD_REG_TIMESTAMP_CTRL, reg);

        cc->read = rkcanfd_timestamp_read;
        cc->mask = CYCLECOUNTER_MASK(32);

        rate = priv->can.clock.freq / div;
        clocks_calc_mult_shift(&cc->mult, &cc->shift, rate, NSEC_PER_SEC,
                               RKCANFD_TIMESTAMP_WORK_MAX_DELAY_SEC);

        max_cycles = div_u64(ULLONG_MAX, cc->mult);
        max_cycles = min(max_cycles, cc->mask);
        work_delay_ns = clocksource_cyc2ns(max_cycles, cc->mult, cc->shift);
        priv->work_delay_jiffies = div_u64(work_delay_ns, 3u * NSEC_PER_SEC / HZ);
        INIT_DELAYED_WORK(&priv->timestamp, rkcanfd_timestamp_work);

        netdev_dbg(priv->ndev, "clock=%lu.%02luMHz bitrate=%lu.%02luMBit/s div=%u rate=%lu.%02luMHz mult=%u shift=%u delay=%lus\n",
                   priv->can.clock.freq / MEGA,
                   priv->can.clock.freq % MEGA / KILO / 10,
                   bitrate / MEGA,
                   bitrate % MEGA / KILO / 100,
                   div,
                   rate / MEGA,
                   rate % MEGA / KILO / 10,
                   cc->mult, cc->shift,
                   priv->work_delay_jiffies / HZ);
}

void rkcanfd_timestamp_start(struct rkcanfd_priv *priv)
{
        timecounter_init(&priv->tc, &priv->cc, ktime_get_real_ns());

        schedule_delayed_work(&priv->timestamp, priv->work_delay_jiffies);
}

void rkcanfd_timestamp_stop(struct rkcanfd_priv *priv)
{
        cancel_delayed_work(&priv->timestamp);
}

void rkcanfd_timestamp_stop_sync(struct rkcanfd_priv *priv)
{
        cancel_delayed_work_sync(&priv->timestamp);
}