/*
 * Copyright (C) Fuzhou Rockchip Electronics Co.Ltd
 * Author: Yakir Yang <ykk@rock-chips.com>
 *
 * This software is licensed under the terms of the GNU General Public
 * License version 2, as published by the Free Software Foundation, and
 * may be copied, distributed, and modified under those terms.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 */

#include <drm/drmP.h>
#include <drm/drm_crtc_helper.h>

#include "rockchip_drm_drv.h"
#include "rockchip_drm_psr.h"

#define PSR_FLUSH_TIMEOUT_MS    100

struct psr_drv {
        struct list_head        list;
        struct drm_encoder      *encoder;

        struct mutex            lock;
        int                     inhibit_count;
        bool                    enabled;

        struct delayed_work     flush_work;

        int (*set)(struct drm_encoder *encoder, bool enable);
};

static struct psr_drv *find_psr_by_encoder(struct drm_encoder *encoder)
{
        struct rockchip_drm_private *drm_drv = encoder->dev->dev_private;
        struct psr_drv *psr;

        mutex_lock(&drm_drv->psr_list_lock);
        list_for_each_entry(psr, &drm_drv->psr_list, list) {
                if (psr->encoder == encoder)
                        goto out;
        }
        psr = ERR_PTR(-ENODEV);

out:
        mutex_unlock(&drm_drv->psr_list_lock);
        return psr;
}

static int psr_set_state_locked(struct psr_drv *psr, bool enable)
{
        int ret;

        if (psr->inhibit_count > 0)
                return -EINVAL;

        if (enable == psr->enabled)
                return 0;

        ret = psr->set(psr->encoder, enable);
        if (ret)
                return ret;

        psr->enabled = enable;
        return 0;
}

static void psr_flush_handler(struct work_struct *work)
{
        struct psr_drv *psr = container_of(to_delayed_work(work),
                                           struct psr_drv, flush_work);

        mutex_lock(&psr->lock);
        psr_set_state_locked(psr, true);
        mutex_unlock(&psr->lock);
}

/**
 * rockchip_drm_psr_inhibit_put - release PSR inhibit on given encoder
 * @encoder: encoder to obtain the PSR encoder
 *
 * Decrements PSR inhibit count on given encoder. Should be called only
 * for a PSR inhibit count increment done before. If PSR inhibit counter
 * reaches zero, PSR flush work is scheduled to make the hardware enter
 * PSR mode in PSR_FLUSH_TIMEOUT_MS.
 *
 * Returns:
 * Zero on success, negative errno on failure.
 */
int rockchip_drm_psr_inhibit_put(struct drm_encoder *encoder)
{
        struct psr_drv *psr = find_psr_by_encoder(encoder);

        if (IS_ERR(psr))
                return PTR_ERR(psr);

        mutex_lock(&psr->lock);
        --psr->inhibit_count;
        WARN_ON(psr->inhibit_count < 0);
        if (!psr->inhibit_count)
                mod_delayed_work(system_wq, &psr->flush_work,
                                 PSR_FLUSH_TIMEOUT_MS);
        mutex_unlock(&psr->lock);

        return 0;
}
EXPORT_SYMBOL(rockchip_drm_psr_inhibit_put);

/**
 * rockchip_drm_psr_inhibit_get - acquire PSR inhibit on given encoder
 * @encoder: encoder to obtain the PSR encoder
 *
 * Increments PSR inhibit count on given encoder. This function guarantees
 * that after it returns PSR is turned off on given encoder and no PSR-related
 * hardware state change occurs at least until a matching call to
 * rockchip_drm_psr_inhibit_put() is done.
 *
 * Returns:
 * Zero on success, negative errno on failure.
 */
int rockchip_drm_psr_inhibit_get(struct drm_encoder *encoder)
{
        struct psr_drv *psr = find_psr_by_encoder(encoder);

        if (IS_ERR(psr))
                return PTR_ERR(psr);

        mutex_lock(&psr->lock);
        psr_set_state_locked(psr, false);
        ++psr->inhibit_count;
        mutex_unlock(&psr->lock);
        cancel_delayed_work_sync(&psr->flush_work);

        return 0;
}
EXPORT_SYMBOL(rockchip_drm_psr_inhibit_get);

static void rockchip_drm_do_flush(struct psr_drv *psr)
{
        cancel_delayed_work_sync(&psr->flush_work);

        mutex_lock(&psr->lock);
        if (!psr_set_state_locked(psr, false))
                mod_delayed_work(system_wq, &psr->flush_work,
                                 PSR_FLUSH_TIMEOUT_MS);
        mutex_unlock(&psr->lock);
}

/**
 * rockchip_drm_psr_flush_all - force to flush all registered PSR encoders
 * @dev: drm device
 *
 * Disable the PSR function for all registered encoders, and then enable the
 * PSR function back after PSR_FLUSH_TIMEOUT. If encoder PSR state have been
 * changed during flush time, then keep the state no change after flush
 * timeout.
 *
 * Returns:
 * Zero on success, negative errno on failure.
 */
void rockchip_drm_psr_flush_all(struct drm_device *dev)
{
        struct rockchip_drm_private *drm_drv = dev->dev_private;
        struct psr_drv *psr;

        mutex_lock(&drm_drv->psr_list_lock);
        list_for_each_entry(psr, &drm_drv->psr_list, list)
                rockchip_drm_do_flush(psr);
        mutex_unlock(&drm_drv->psr_list_lock);
}
EXPORT_SYMBOL(rockchip_drm_psr_flush_all);

/**
 * rockchip_drm_psr_register - register encoder to psr driver
 * @encoder: encoder that obtain the PSR function
 * @psr_set: call back to set PSR state
 *
 * The function returns with PSR inhibit counter initialized with one
 * and the caller (typically encoder driver) needs to call
 * rockchip_drm_psr_inhibit_put() when it becomes ready to accept PSR
 * enable request.
 *
 * Returns:
 * Zero on success, negative errno on failure.
 */
int rockchip_drm_psr_register(struct drm_encoder *encoder,
                        int (*psr_set)(struct drm_encoder *, bool enable))
{
        struct rockchip_drm_private *drm_drv = encoder->dev->dev_private;
        struct psr_drv *psr;

        if (!encoder || !psr_set)
                return -EINVAL;

        psr = kzalloc(sizeof(struct psr_drv), GFP_KERNEL);
        if (!psr)
                return -ENOMEM;

        INIT_DELAYED_WORK(&psr->flush_work, psr_flush_handler);
        mutex_init(&psr->lock);

        psr->inhibit_count = 1;
        psr->enabled = false;
        psr->encoder = encoder;
        psr->set = psr_set;

        mutex_lock(&drm_drv->psr_list_lock);
        list_add_tail(&psr->list, &drm_drv->psr_list);
        mutex_unlock(&drm_drv->psr_list_lock);

        return 0;
}
EXPORT_SYMBOL(rockchip_drm_psr_register);

/**
 * rockchip_drm_psr_unregister - unregister encoder to psr driver
 * @encoder: encoder that obtain the PSR function
 * @psr_set: call back to set PSR state
 *
 * It is expected that the PSR inhibit counter is 1 when this function is
 * called, which corresponds to a state when related encoder has been
 * disconnected from any CRTCs and its driver called
 * rockchip_drm_psr_inhibit_get() to stop the PSR logic.
 *
 * Returns:
 * Zero on success, negative errno on failure.
 */
void rockchip_drm_psr_unregister(struct drm_encoder *encoder)
{
        struct rockchip_drm_private *drm_drv = encoder->dev->dev_private;
        struct psr_drv *psr, *n;

        mutex_lock(&drm_drv->psr_list_lock);
        list_for_each_entry_safe(psr, n, &drm_drv->psr_list, list) {
                if (psr->encoder == encoder) {
                        /*
                         * Any other value would mean that the encoder
                         * is still in use.
                         */
                        WARN_ON(psr->inhibit_count != 1);

                        list_del(&psr->list);
                        kfree(psr);
                }
        }
        mutex_unlock(&drm_drv->psr_list_lock);
}
EXPORT_SYMBOL(rockchip_drm_psr_unregister);