/*
 * Copyright © 2015 Intel Corporation
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice (including the next
 * paragraph) shall be included in all copies or substantial portions of the
 * Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
 * IN THE SOFTWARE.
 */

#include <linux/debugfs.h>
#include <linux/kernel.h>

#include <drm/drm_print.h>
#include <drm/drm_probe_helper.h>

#include "intel_connector.h"
#include "intel_display_core.h"
#include "intel_display_power.h"
#include "intel_display_rpm.h"
#include "intel_display_types.h"
#include "intel_display_utils.h"
#include "intel_dp.h"
#include "intel_hdcp.h"
#include "intel_hotplug.h"
#include "intel_hotplug_irq.h"
#include "intel_parent.h"

/**
 * DOC: Hotplug
 *
 * Simply put, hotplug occurs when a display is connected to or disconnected
 * from the system. However, there may be adapters and docking stations and
 * Display Port short pulses and MST devices involved, complicating matters.
 *
 * Hotplug in i915 is handled in many different levels of abstraction.
 *
 * The platform dependent interrupt handling code in i915_irq.c enables,
 * disables, and does preliminary handling of the interrupts. The interrupt
 * handlers gather the hotplug detect (HPD) information from relevant registers
 * into a platform independent mask of hotplug pins that have fired.
 *
 * The platform independent interrupt handler intel_hpd_irq_handler() in
 * intel_hotplug.c does hotplug irq storm detection and mitigation, and passes
 * further processing to appropriate bottom halves (Display Port specific and
 * regular hotplug).
 *
 * The Display Port work function i915_digport_work_func() calls into
 * intel_dp_hpd_pulse() via hooks, which handles DP short pulses and DP MST long
 * pulses, with failures and non-MST long pulses triggering regular hotplug
 * processing on the connector.
 *
 * The regular hotplug work function i915_hotplug_work_func() calls connector
 * detect hooks, and, if connector status changes, triggers sending of hotplug
 * uevent to userspace via drm_kms_helper_hotplug_event().
 *
 * Finally, the userspace is responsible for triggering a modeset upon receiving
 * the hotplug uevent, disabling or enabling the crtc as needed.
 *
 * The hotplug interrupt storm detection and mitigation code keeps track of the
 * number of interrupts per hotplug pin per a period of time, and if the number
 * of interrupts exceeds a certain threshold, the interrupt is disabled for a
 * while before being re-enabled. The intention is to mitigate issues raising
 * from broken hardware triggering massive amounts of interrupts and grinding
 * the system to a halt.
 *
 * Current implementation expects that hotplug interrupt storm will not be
 * seen when display port sink is connected, hence on platforms whose DP
 * callback is handled by i915_digport_work_func reenabling of hpd is not
 * performed (it was never expected to be disabled in the first place ;) )
 * this is specific to DP sinks handled by this routine and any other display
 * such as HDMI or DVI enabled on the same port will have proper logic since
 * it will use i915_hotplug_work_func where this logic is handled.
 */

/**
 * intel_hpd_pin_default - return default pin associated with certain port.
 * @port: the hpd port to get associated pin
 *
 * It is only valid and used by digital port encoder.
 *
 * Return pin that is associatade with @port.
 */
enum hpd_pin intel_hpd_pin_default(enum port port)
{
        return HPD_PORT_A + port - PORT_A;
}

/* Threshold == 5 for long IRQs, 50 for short */
#define HPD_STORM_DEFAULT_THRESHOLD     50

#define HPD_STORM_DETECT_PERIOD         1000
#define HPD_STORM_REENABLE_DELAY        (2 * 60 * 1000)
#define HPD_RETRY_DELAY                 1000

static enum hpd_pin
intel_connector_hpd_pin(struct intel_connector *connector)
{
        struct intel_encoder *encoder = intel_attached_encoder(connector);

        /*
         * MST connectors get their encoder attached dynamically
         * so need to make sure we have an encoder here. But since
         * MST encoders have their hpd_pin set to HPD_NONE we don't
         * have to special case them beyond that.
         */
        return encoder ? encoder->hpd_pin : HPD_NONE;
}

/**
 * intel_hpd_irq_storm_detect - gather stats and detect HPD IRQ storm on a pin
 * @display: display device
 * @pin: the pin to gather stats on
 * @long_hpd: whether the HPD IRQ was long or short
 *
 * Gather stats about HPD IRQs from the specified @pin, and detect IRQ
 * storms. Only the pin specific stats and state are changed, the caller is
 * responsible for further action.
 *
 * The number of IRQs that are allowed within @HPD_STORM_DETECT_PERIOD is
 * stored in @display->hotplug.hpd_storm_threshold which defaults to
 * @HPD_STORM_DEFAULT_THRESHOLD. Long IRQs count as +10 to this threshold, and
 * short IRQs count as +1. If this threshold is exceeded, it's considered an
 * IRQ storm and the IRQ state is set to @HPD_MARK_DISABLED.
 *
 * By default, most systems will only count long IRQs towards
 * &display->hotplug.hpd_storm_threshold. However, some older systems also
 * suffer from short IRQ storms and must also track these. Because short IRQ
 * storms are naturally caused by sideband interactions with DP MST devices,
 * short IRQ detection is only enabled for systems without DP MST support.
 * Systems which are new enough to support DP MST are far less likely to
 * suffer from IRQ storms at all, so this is fine.
 *
 * The HPD threshold can be controlled through i915_hpd_storm_ctl in debugfs,
 * and should only be adjusted for automated hotplug testing.
 *
 * Return true if an IRQ storm was detected on @pin.
 */
static bool intel_hpd_irq_storm_detect(struct intel_display *display,
                                       enum hpd_pin pin, bool long_hpd)
{
        struct intel_hotplug *hpd = &display->hotplug;
        unsigned long start = hpd->stats[pin].last_jiffies;
        unsigned long end = start + msecs_to_jiffies(HPD_STORM_DETECT_PERIOD);
        const int increment = long_hpd ? 10 : 1;
        const int threshold = hpd->hpd_storm_threshold;
        bool storm = false;

        if (!threshold ||
            (!long_hpd && !display->hotplug.hpd_short_storm_enabled))
                return false;

        if (!time_in_range(jiffies, start, end)) {
                hpd->stats[pin].last_jiffies = jiffies;
                hpd->stats[pin].count = 0;
        }

        hpd->stats[pin].count += increment;
        if (hpd->stats[pin].count > threshold) {
                hpd->stats[pin].state = HPD_MARK_DISABLED;
                drm_dbg_kms(display->drm,
                            "HPD interrupt storm detected on PIN %d\n", pin);
                storm = true;
        } else {
                drm_dbg_kms(display->drm,
                            "Received HPD interrupt on PIN %d - cnt: %d\n",
                              pin,
                              hpd->stats[pin].count);
        }

        return storm;
}

static bool detection_work_enabled(struct intel_display *display)
{
        lockdep_assert_held(&display->irq.lock);

        return display->hotplug.detection_work_enabled;
}

static bool
mod_delayed_detection_work(struct intel_display *display, struct delayed_work *work, int delay)
{
        lockdep_assert_held(&display->irq.lock);

        if (!detection_work_enabled(display))
                return false;

        return mod_delayed_work(display->wq.unordered, work, delay);
}

static bool
queue_delayed_detection_work(struct intel_display *display, struct delayed_work *work, int delay)
{
        lockdep_assert_held(&display->irq.lock);

        if (!detection_work_enabled(display))
                return false;

        return queue_delayed_work(display->wq.unordered, work, delay);
}

static bool
queue_detection_work(struct intel_display *display, struct work_struct *work)
{
        lockdep_assert_held(&display->irq.lock);

        if (!detection_work_enabled(display))
                return false;

        return queue_work(display->wq.unordered, work);
}

static void
intel_hpd_irq_storm_switch_to_polling(struct intel_display *display)
{
        struct drm_connector_list_iter conn_iter;
        struct intel_connector *connector;
        bool hpd_disabled = false;

        lockdep_assert_held(&display->irq.lock);

        drm_connector_list_iter_begin(display->drm, &conn_iter);
        for_each_intel_connector_iter(connector, &conn_iter) {
                enum hpd_pin pin;

                if (connector->base.polled != DRM_CONNECTOR_POLL_HPD)
                        continue;

                pin = intel_connector_hpd_pin(connector);
                if (pin == HPD_NONE ||
                    display->hotplug.stats[pin].state != HPD_MARK_DISABLED)
                        continue;

                drm_info(display->drm,
                         "HPD interrupt storm detected on connector %s: "
                         "switching from hotplug detection to polling\n",
                         connector->base.name);

                display->hotplug.stats[pin].state = HPD_DISABLED;
                connector->base.polled = DRM_CONNECTOR_POLL_CONNECT |
                        DRM_CONNECTOR_POLL_DISCONNECT;
                hpd_disabled = true;
        }
        drm_connector_list_iter_end(&conn_iter);

        /* Enable polling and queue hotplug re-enabling. */
        if (hpd_disabled) {
                drm_kms_helper_poll_reschedule(display->drm);
                mod_delayed_detection_work(display,
                                           &display->hotplug.reenable_work,
                                           msecs_to_jiffies(HPD_STORM_REENABLE_DELAY));
        }
}

static void intel_hpd_irq_storm_reenable_work(struct work_struct *work)
{
        struct intel_display *display =
                container_of(work, typeof(*display), hotplug.reenable_work.work);
        struct drm_connector_list_iter conn_iter;
        struct intel_connector *connector;
        struct ref_tracker *wakeref;
        enum hpd_pin pin;

        wakeref = intel_display_rpm_get(display);

        spin_lock_irq(&display->irq.lock);

        drm_connector_list_iter_begin(display->drm, &conn_iter);
        for_each_intel_connector_iter(connector, &conn_iter) {
                pin = intel_connector_hpd_pin(connector);
                if (pin == HPD_NONE ||
                    display->hotplug.stats[pin].state != HPD_DISABLED)
                        continue;

                if (connector->base.polled != connector->polled)
                        drm_dbg(display->drm,
                                "Reenabling HPD on connector %s\n",
                                connector->base.name);
                connector->base.polled = connector->polled;
        }
        drm_connector_list_iter_end(&conn_iter);

        for_each_hpd_pin(pin) {
                if (display->hotplug.stats[pin].state == HPD_DISABLED)
                        display->hotplug.stats[pin].state = HPD_ENABLED;
        }

        intel_hpd_irq_setup(display);

        spin_unlock_irq(&display->irq.lock);

        intel_display_rpm_put(display, wakeref);
}

static enum intel_hotplug_state
intel_hotplug_detect_connector(struct intel_connector *connector)
{
        struct drm_device *dev = connector->base.dev;
        enum drm_connector_status old_status;
        u64 old_epoch_counter;
        int status;
        bool ret = false;

        drm_WARN_ON(dev, !mutex_is_locked(&dev->mode_config.mutex));
        old_status = connector->base.status;
        old_epoch_counter = connector->base.epoch_counter;

        status = drm_helper_probe_detect(&connector->base, NULL, false);
        if (!connector->base.force)
                connector->base.status = status;

        if (old_epoch_counter != connector->base.epoch_counter)
                ret = true;

        if (ret) {
                drm_dbg_kms(dev, "[CONNECTOR:%d:%s] status updated from %s to %s (epoch counter %llu->%llu)\n",
                            connector->base.base.id,
                            connector->base.name,
                            drm_get_connector_status_name(old_status),
                            drm_get_connector_status_name(connector->base.status),
                            old_epoch_counter,
                            connector->base.epoch_counter);
                return INTEL_HOTPLUG_CHANGED;
        }
        return INTEL_HOTPLUG_UNCHANGED;
}

enum intel_hotplug_state
intel_encoder_hotplug(struct intel_encoder *encoder,
                      struct intel_connector *connector)
{
        return intel_hotplug_detect_connector(connector);
}

static bool intel_encoder_has_hpd_pulse(struct intel_encoder *encoder)
{
        return intel_encoder_is_dig_port(encoder) &&
                enc_to_dig_port(encoder)->hpd_pulse != NULL;
}

static bool hpd_pin_has_pulse(struct intel_display *display, enum hpd_pin pin)
{
        struct intel_encoder *encoder;

        for_each_intel_encoder(display->drm, encoder) {
                if (encoder->hpd_pin != pin)
                        continue;

                if (intel_encoder_has_hpd_pulse(encoder))
                        return true;
        }

        return false;
}

static bool hpd_pin_is_blocked(struct intel_display *display, enum hpd_pin pin)
{
        lockdep_assert_held(&display->irq.lock);

        return display->hotplug.stats[pin].blocked_count;
}

static u32 get_blocked_hpd_pin_mask(struct intel_display *display)
{
        enum hpd_pin pin;
        u32 hpd_pin_mask = 0;

        for_each_hpd_pin(pin) {
                if (hpd_pin_is_blocked(display, pin))
                        hpd_pin_mask |= BIT(pin);
        }

        return hpd_pin_mask;
}

static void i915_digport_work_func(struct work_struct *work)
{
        struct intel_display *display =
                container_of(work, struct intel_display, hotplug.dig_port_work);
        struct intel_hotplug *hotplug = &display->hotplug;
        u32 long_hpd_pin_mask, short_hpd_pin_mask;
        struct intel_encoder *encoder;
        u32 blocked_hpd_pin_mask;
        u32 old_bits = 0;

        spin_lock_irq(&display->irq.lock);

        blocked_hpd_pin_mask = get_blocked_hpd_pin_mask(display);
        long_hpd_pin_mask = hotplug->long_hpd_pin_mask & ~blocked_hpd_pin_mask;
        hotplug->long_hpd_pin_mask &= ~long_hpd_pin_mask;
        short_hpd_pin_mask = hotplug->short_hpd_pin_mask & ~blocked_hpd_pin_mask;
        hotplug->short_hpd_pin_mask &= ~short_hpd_pin_mask;

        spin_unlock_irq(&display->irq.lock);

        for_each_intel_encoder(display->drm, encoder) {
                struct intel_digital_port *dig_port;
                enum hpd_pin pin = encoder->hpd_pin;
                bool long_hpd, short_hpd;
                enum irqreturn ret;

                if (!intel_encoder_has_hpd_pulse(encoder))
                        continue;

                long_hpd = long_hpd_pin_mask & BIT(pin);
                short_hpd = short_hpd_pin_mask & BIT(pin);

                if (!long_hpd && !short_hpd)
                        continue;

                dig_port = enc_to_dig_port(encoder);

                ret = dig_port->hpd_pulse(dig_port, long_hpd);
                if (ret == IRQ_NONE) {
                        /* fall back to old school hpd */
                        old_bits |= BIT(pin);
                }
        }

        if (old_bits) {
                spin_lock_irq(&display->irq.lock);
                display->hotplug.event_bits |= old_bits;
                queue_delayed_detection_work(display,
                                             &display->hotplug.hotplug_work, 0);
                spin_unlock_irq(&display->irq.lock);
        }
}

/**
 * intel_hpd_trigger_irq - trigger an hpd irq event for a port
 * @dig_port: digital port
 *
 * Trigger an HPD interrupt event for the given port, emulating a short pulse
 * generated by the sink, and schedule the dig port work to handle it.
 */
void intel_hpd_trigger_irq(struct intel_digital_port *dig_port)
{
        struct intel_display *display = to_intel_display(dig_port);
        struct intel_hotplug *hotplug = &display->hotplug;
        struct intel_encoder *encoder = &dig_port->base;

        spin_lock_irq(&display->irq.lock);

        hotplug->short_hpd_pin_mask |= BIT(encoder->hpd_pin);
        if (!hpd_pin_is_blocked(display, encoder->hpd_pin))
                queue_work(hotplug->dp_wq, &hotplug->dig_port_work);

        spin_unlock_irq(&display->irq.lock);
}

/*
 * Handle hotplug events outside the interrupt handler proper.
 */
static void i915_hotplug_work_func(struct work_struct *work)
{
        struct intel_display *display =
                container_of(work, struct intel_display, hotplug.hotplug_work.work);
        struct intel_hotplug *hotplug = &display->hotplug;
        struct drm_connector_list_iter conn_iter;
        struct intel_connector *connector;
        u32 changed = 0, retry = 0;
        u32 hpd_event_bits;
        u32 hpd_retry_bits;
        struct drm_connector *first_changed_connector = NULL;
        int changed_connectors = 0;
        u32 blocked_hpd_pin_mask;

        mutex_lock(&display->drm->mode_config.mutex);
        drm_dbg_kms(display->drm, "running encoder hotplug functions\n");

        spin_lock_irq(&display->irq.lock);

        blocked_hpd_pin_mask = get_blocked_hpd_pin_mask(display);
        hpd_event_bits = hotplug->event_bits & ~blocked_hpd_pin_mask;
        hotplug->event_bits &= ~hpd_event_bits;
        hpd_retry_bits = hotplug->retry_bits & ~blocked_hpd_pin_mask;
        hotplug->retry_bits &= ~hpd_retry_bits;

        /* Enable polling for connectors which had HPD IRQ storms */
        intel_hpd_irq_storm_switch_to_polling(display);

        spin_unlock_irq(&display->irq.lock);

        /* Skip calling encode hotplug handlers if ignore long HPD set*/
        if (display->hotplug.ignore_long_hpd) {
                drm_dbg_kms(display->drm, "Ignore HPD flag on - skip encoder hotplug handlers\n");
                mutex_unlock(&display->drm->mode_config.mutex);
                return;
        }

        drm_connector_list_iter_begin(display->drm, &conn_iter);
        for_each_intel_connector_iter(connector, &conn_iter) {
                enum hpd_pin pin;
                u32 hpd_bit;

                pin = intel_connector_hpd_pin(connector);
                if (pin == HPD_NONE)
                        continue;

                hpd_bit = BIT(pin);
                if ((hpd_event_bits | hpd_retry_bits) & hpd_bit) {
                        struct intel_encoder *encoder =
                                intel_attached_encoder(connector);

                        if (hpd_event_bits & hpd_bit)
                                connector->hotplug_retries = 0;
                        else
                                connector->hotplug_retries++;

                        drm_dbg_kms(display->drm,
                                    "Connector %s (pin %i) received hotplug event. (retry %d)\n",
                                    connector->base.name, pin,
                                    connector->hotplug_retries);

                        switch (encoder->hotplug(encoder, connector)) {
                        case INTEL_HOTPLUG_UNCHANGED:
                                break;
                        case INTEL_HOTPLUG_CHANGED:
                                changed |= hpd_bit;
                                changed_connectors++;
                                if (!first_changed_connector) {
                                        drm_connector_get(&connector->base);
                                        first_changed_connector = &connector->base;
                                }
                                break;
                        case INTEL_HOTPLUG_RETRY:
                                retry |= hpd_bit;
                                break;
                        }
                }
        }
        drm_connector_list_iter_end(&conn_iter);
        mutex_unlock(&display->drm->mode_config.mutex);

        if (changed_connectors == 1)
                drm_kms_helper_connector_hotplug_event(first_changed_connector);
        else if (changed_connectors > 0)
                drm_kms_helper_hotplug_event(display->drm);

        if (first_changed_connector)
                drm_connector_put(first_changed_connector);

        /* Remove shared HPD pins that have changed */
        retry &= ~changed;
        if (retry) {
                spin_lock_irq(&display->irq.lock);
                display->hotplug.retry_bits |= retry;

                mod_delayed_detection_work(display,
                                           &display->hotplug.hotplug_work,
                                           msecs_to_jiffies(HPD_RETRY_DELAY));
                spin_unlock_irq(&display->irq.lock);
        }
}


/**
 * intel_hpd_irq_handler - main hotplug irq handler
 * @display: display device
 * @pin_mask: a mask of hpd pins that have triggered the irq
 * @long_mask: a mask of hpd pins that may be long hpd pulses
 *
 * This is the main hotplug irq handler for all platforms. The platform specific
 * irq handlers call the platform specific hotplug irq handlers, which read and
 * decode the appropriate registers into bitmasks about hpd pins that have
 * triggered (@pin_mask), and which of those pins may be long pulses
 * (@long_mask). The @long_mask is ignored if the port corresponding to the pin
 * is not a digital port.
 *
 * Here, we do hotplug irq storm detection and mitigation, and pass further
 * processing to appropriate bottom halves.
 */
void intel_hpd_irq_handler(struct intel_display *display,
                           u32 pin_mask, u32 long_mask)
{
        struct intel_encoder *encoder;
        bool storm_detected = false;
        bool queue_dig = false, queue_hp = false;
        u32 long_hpd_pulse_mask = 0;
        u32 short_hpd_pulse_mask = 0;
        enum hpd_pin pin;

        if (!pin_mask)
                return;

        spin_lock(&display->irq.lock);

        /*
         * Determine whether ->hpd_pulse() exists for each pin, and
         * whether we have a short or a long pulse. This is needed
         * as each pin may have up to two encoders (HDMI and DP) and
         * only the one of them (DP) will have ->hpd_pulse().
         */
        for_each_intel_encoder(display->drm, encoder) {
                bool long_hpd;

                pin = encoder->hpd_pin;
                if (!(BIT(pin) & pin_mask))
                        continue;

                if (!intel_encoder_has_hpd_pulse(encoder))
                        continue;

                long_hpd = long_mask & BIT(pin);

                drm_dbg(display->drm,
                        "digital hpd on [ENCODER:%d:%s] - %s\n",
                        encoder->base.base.id, encoder->base.name,
                        long_hpd ? "long" : "short");

                if (!hpd_pin_is_blocked(display, pin))
                        queue_dig = true;

                if (long_hpd) {
                        long_hpd_pulse_mask |= BIT(pin);
                        display->hotplug.long_hpd_pin_mask |= BIT(pin);
                } else {
                        short_hpd_pulse_mask |= BIT(pin);
                        display->hotplug.short_hpd_pin_mask |= BIT(pin);
                }
        }

        /* Now process each pin just once */
        for_each_hpd_pin(pin) {
                bool long_hpd;

                if (!(BIT(pin) & pin_mask))
                        continue;

                if (display->hotplug.stats[pin].state == HPD_DISABLED) {
                        /*
                         * On GMCH platforms the interrupt mask bits only
                         * prevent irq generation, not the setting of the
                         * hotplug bits itself. So only WARN about unexpected
                         * interrupts on saner platforms.
                         */
                        drm_WARN_ONCE(display->drm, !HAS_GMCH(display),
                                      "Received HPD interrupt on pin %d although disabled\n",
                                      pin);
                        continue;
                }

                if (display->hotplug.stats[pin].state != HPD_ENABLED)
                        continue;

                /*
                 * Delegate to ->hpd_pulse() if one of the encoders for this
                 * pin has it, otherwise let the hotplug_work deal with this
                 * pin directly.
                 */
                if (((short_hpd_pulse_mask | long_hpd_pulse_mask) & BIT(pin))) {
                        long_hpd = long_hpd_pulse_mask & BIT(pin);
                } else {
                        display->hotplug.event_bits |= BIT(pin);
                        long_hpd = true;

                        if (!hpd_pin_is_blocked(display, pin))
                                queue_hp = true;
                }

                if (intel_hpd_irq_storm_detect(display, pin, long_hpd)) {
                        display->hotplug.event_bits &= ~BIT(pin);
                        storm_detected = true;
                        queue_hp = true;
                }
        }

        /*
         * Disable any IRQs that storms were detected on. Polling enablement
         * happens later in our hotplug work.
         */
        if (storm_detected)
                intel_hpd_irq_setup(display);

        /*
         * Our hotplug handler can grab modeset locks (by calling down into the
         * fb helpers). Hence it must not be run on our own dev-priv->wq work
         * queue for otherwise the flush_work in the pageflip code will
         * deadlock.
         */
        if (queue_dig)
                queue_work(display->hotplug.dp_wq, &display->hotplug.dig_port_work);
        if (queue_hp)
                queue_delayed_detection_work(display,
                                             &display->hotplug.hotplug_work, 0);

        spin_unlock(&display->irq.lock);
}

/**
 * intel_hpd_init - initializes and enables hpd support
 * @display: display device instance
 *
 * This function enables the hotplug support. It requires that interrupts have
 * already been enabled with intel_irq_init_hw(). From this point on hotplug and
 * poll request can run concurrently to other code, so locking rules must be
 * obeyed.
 *
 * This is a separate step from interrupt enabling to simplify the locking rules
 * in the driver load and resume code.
 *
 * Also see: intel_hpd_poll_enable() and intel_hpd_poll_disable().
 */
void intel_hpd_init(struct intel_display *display)
{
        int i;

        if (!HAS_DISPLAY(display))
                return;

        for_each_hpd_pin(i) {
                display->hotplug.stats[i].count = 0;
                display->hotplug.stats[i].state = HPD_ENABLED;
        }

        /*
         * Interrupt setup is already guaranteed to be single-threaded, this is
         * just to make the assert_spin_locked checks happy.
         */
        spin_lock_irq(&display->irq.lock);
        intel_hpd_irq_setup(display);
        spin_unlock_irq(&display->irq.lock);
}

static void i915_hpd_poll_detect_connectors(struct intel_display *display)
{
        struct drm_connector_list_iter conn_iter;
        struct intel_connector *connector;
        struct intel_connector *first_changed_connector = NULL;
        int changed = 0;

        mutex_lock(&display->drm->mode_config.mutex);

        if (!display->drm->mode_config.poll_enabled)
                goto out;

        drm_connector_list_iter_begin(display->drm, &conn_iter);
        for_each_intel_connector_iter(connector, &conn_iter) {
                if (!(connector->base.polled & DRM_CONNECTOR_POLL_HPD))
                        continue;

                if (intel_hotplug_detect_connector(connector) != INTEL_HOTPLUG_CHANGED)
                        continue;

                changed++;

                if (changed == 1) {
                        drm_connector_get(&connector->base);
                        first_changed_connector = connector;
                }
        }
        drm_connector_list_iter_end(&conn_iter);

out:
        mutex_unlock(&display->drm->mode_config.mutex);

        if (!changed)
                return;

        if (changed == 1)
                drm_kms_helper_connector_hotplug_event(&first_changed_connector->base);
        else
                drm_kms_helper_hotplug_event(display->drm);

        drm_connector_put(&first_changed_connector->base);
}

static void i915_hpd_poll_init_work(struct work_struct *work)
{
        struct intel_display *display =
                container_of(work, typeof(*display), hotplug.poll_init_work);
        struct drm_connector_list_iter conn_iter;
        struct intel_connector *connector;
        struct ref_tracker *wakeref;
        bool enabled;

        mutex_lock(&display->drm->mode_config.mutex);

        enabled = READ_ONCE(display->hotplug.poll_enabled);
        /*
         * Prevent taking a power reference from this sequence of
         * i915_hpd_poll_init_work() -> drm_helper_hpd_irq_event() ->
         * connector detect which would requeue i915_hpd_poll_init_work()
         * and so risk an endless loop of this same sequence.
         */
        if (!enabled) {
                wakeref = intel_display_power_get(display,
                                                  POWER_DOMAIN_DISPLAY_CORE);
                drm_WARN_ON(display->drm,
                            READ_ONCE(display->hotplug.poll_enabled));
                cancel_work(&display->hotplug.poll_init_work);
        }

        spin_lock_irq(&display->irq.lock);

        drm_connector_list_iter_begin(display->drm, &conn_iter);
        for_each_intel_connector_iter(connector, &conn_iter) {
                enum hpd_pin pin;

                pin = intel_connector_hpd_pin(connector);
                if (pin == HPD_NONE)
                        continue;

                if (display->hotplug.stats[pin].state == HPD_DISABLED)
                        continue;

                connector->base.polled = connector->polled;

                if (enabled && connector->base.polled == DRM_CONNECTOR_POLL_HPD)
                        connector->base.polled = DRM_CONNECTOR_POLL_CONNECT |
                                DRM_CONNECTOR_POLL_DISCONNECT;
        }
        drm_connector_list_iter_end(&conn_iter);

        spin_unlock_irq(&display->irq.lock);

        if (enabled)
                drm_kms_helper_poll_reschedule(display->drm);

        mutex_unlock(&display->drm->mode_config.mutex);

        /*
         * We might have missed any hotplugs that happened while we were
         * in the middle of disabling polling
         */
        if (!enabled) {
                i915_hpd_poll_detect_connectors(display);

                intel_display_power_put(display,
                                        POWER_DOMAIN_DISPLAY_CORE,
                                        wakeref);
        }
}

/**
 * intel_hpd_poll_enable - enable polling for connectors with hpd
 * @display: display device instance
 *
 * This function enables polling for all connectors which support HPD.
 * Under certain conditions HPD may not be functional. On most Intel GPUs,
 * this happens when we enter runtime suspend.
 * On Valleyview and Cherryview systems, this also happens when we shut off all
 * of the powerwells.
 *
 * Since this function can get called in contexts where we're already holding
 * dev->mode_config.mutex, we do the actual hotplug enabling in a separate
 * worker.
 *
 * Also see: intel_hpd_init() and intel_hpd_poll_disable().
 */
void intel_hpd_poll_enable(struct intel_display *display)
{
        if (!HAS_DISPLAY(display) || !intel_display_device_enabled(display))
                return;

        WRITE_ONCE(display->hotplug.poll_enabled, true);

        /*
         * We might already be holding dev->mode_config.mutex, so do this in a
         * separate worker
         * As well, there's no issue if we race here since we always reschedule
         * this worker anyway
         */
        spin_lock_irq(&display->irq.lock);
        queue_detection_work(display,
                             &display->hotplug.poll_init_work);
        spin_unlock_irq(&display->irq.lock);
}

/**
 * intel_hpd_poll_disable - disable polling for connectors with hpd
 * @display: display device instance
 *
 * This function disables polling for all connectors which support HPD.
 * Under certain conditions HPD may not be functional. On most Intel GPUs,
 * this happens when we enter runtime suspend.
 * On Valleyview and Cherryview systems, this also happens when we shut off all
 * of the powerwells.
 *
 * Since this function can get called in contexts where we're already holding
 * dev->mode_config.mutex, we do the actual hotplug enabling in a separate
 * worker.
 *
 * Also used during driver init to initialize connector->polled
 * appropriately for all connectors.
 *
 * Also see: intel_hpd_init() and intel_hpd_poll_enable().
 */
void intel_hpd_poll_disable(struct intel_display *display)
{
        struct intel_encoder *encoder;

        if (!HAS_DISPLAY(display))
                return;

        for_each_intel_dp(display->drm, encoder)
                intel_dp_dpcd_set_probe(enc_to_intel_dp(encoder), true);

        WRITE_ONCE(display->hotplug.poll_enabled, false);

        spin_lock_irq(&display->irq.lock);
        queue_detection_work(display,
                             &display->hotplug.poll_init_work);
        spin_unlock_irq(&display->irq.lock);
}

void intel_hpd_poll_fini(struct intel_display *display)
{
        struct intel_connector *connector;
        struct drm_connector_list_iter conn_iter;

        /* Kill all the work that may have been queued by hpd. */
        drm_connector_list_iter_begin(display->drm, &conn_iter);
        for_each_intel_connector_iter(connector, &conn_iter) {
                intel_connector_cancel_modeset_retry_work(connector);
                intel_hdcp_cancel_works(connector);
        }
        drm_connector_list_iter_end(&conn_iter);
}

void intel_hpd_init_early(struct intel_display *display)
{
        INIT_DELAYED_WORK(&display->hotplug.hotplug_work,
                          i915_hotplug_work_func);
        INIT_WORK(&display->hotplug.dig_port_work, i915_digport_work_func);
        INIT_WORK(&display->hotplug.poll_init_work, i915_hpd_poll_init_work);
        INIT_DELAYED_WORK(&display->hotplug.reenable_work,
                          intel_hpd_irq_storm_reenable_work);

        display->hotplug.hpd_storm_threshold = HPD_STORM_DEFAULT_THRESHOLD;
        /* If we have MST support, we want to avoid doing short HPD IRQ storm
         * detection, as short HPD storms will occur as a natural part of
         * sideband messaging with MST.
         * On older platforms however, IRQ storms can occur with both long and
         * short pulses, as seen on some G4x systems.
         */
        display->hotplug.hpd_short_storm_enabled = !HAS_DP_MST(display);
}

static bool cancel_all_detection_work(struct intel_display *display)
{
        bool was_pending = false;

        if (cancel_delayed_work_sync(&display->hotplug.hotplug_work))
                was_pending = true;
        if (cancel_work_sync(&display->hotplug.poll_init_work))
                was_pending = true;
        if (cancel_delayed_work_sync(&display->hotplug.reenable_work))
                was_pending = true;

        return was_pending;
}

void intel_hpd_cancel_work(struct intel_display *display)
{
        if (!HAS_DISPLAY(display))
                return;

        spin_lock_irq(&display->irq.lock);

        display->hotplug.long_hpd_pin_mask = 0;
        display->hotplug.short_hpd_pin_mask = 0;
        display->hotplug.event_bits = 0;
        display->hotplug.retry_bits = 0;

        spin_unlock_irq(&display->irq.lock);

        cancel_work_sync(&display->hotplug.dig_port_work);

        /*
         * All other work triggered by hotplug events should be canceled by
         * now.
         */
        if (cancel_all_detection_work(display))
                drm_dbg_kms(display->drm, "Hotplug detection work still active\n");
}

static void queue_work_for_missed_irqs(struct intel_display *display)
{
        struct intel_hotplug *hotplug = &display->hotplug;
        bool queue_hp_work = false;
        u32 blocked_hpd_pin_mask;
        enum hpd_pin pin;

        lockdep_assert_held(&display->irq.lock);

        blocked_hpd_pin_mask = get_blocked_hpd_pin_mask(display);
        if ((hotplug->event_bits | hotplug->retry_bits) & ~blocked_hpd_pin_mask)
                queue_hp_work = true;

        for_each_hpd_pin(pin) {
                switch (display->hotplug.stats[pin].state) {
                case HPD_MARK_DISABLED:
                        queue_hp_work = true;
                        break;
                case HPD_DISABLED:
                case HPD_ENABLED:
                        break;
                default:
                        MISSING_CASE(display->hotplug.stats[pin].state);
                }
        }

        if ((hotplug->long_hpd_pin_mask | hotplug->short_hpd_pin_mask) & ~blocked_hpd_pin_mask)
                queue_work(hotplug->dp_wq, &hotplug->dig_port_work);

        if (queue_hp_work)
                queue_delayed_detection_work(display, &display->hotplug.hotplug_work, 0);
}

static bool block_hpd_pin(struct intel_display *display, enum hpd_pin pin)
{
        struct intel_hotplug *hotplug = &display->hotplug;

        lockdep_assert_held(&display->irq.lock);

        hotplug->stats[pin].blocked_count++;

        return hotplug->stats[pin].blocked_count == 1;
}

static bool unblock_hpd_pin(struct intel_display *display, enum hpd_pin pin)
{
        struct intel_hotplug *hotplug = &display->hotplug;

        lockdep_assert_held(&display->irq.lock);

        if (drm_WARN_ON(display->drm, hotplug->stats[pin].blocked_count == 0))
                return true;

        hotplug->stats[pin].blocked_count--;

        return hotplug->stats[pin].blocked_count == 0;
}

/**
 * intel_hpd_block - Block handling of HPD IRQs on an HPD pin
 * @encoder: Encoder to block the HPD handling for
 *
 * Blocks the handling of HPD IRQs on the HPD pin of @encoder.
 *
 * On return:
 *
 * - It's guaranteed that the blocked encoders' HPD pulse handler
 *   (via intel_digital_port::hpd_pulse()) is not running.
 * - The hotplug event handling (via intel_encoder::hotplug()) of an
 *   HPD IRQ pending at the time this function is called may be still
 *   running.
 * - Detection on the encoder's connector (via
 *   drm_connector_helper_funcs::detect_ctx(),
 *   drm_connector_funcs::detect()) remains allowed, for instance as part of
 *   userspace connector probing, or DRM core's connector polling.
 *
 * The call must be followed by calling intel_hpd_unblock(), or
 * intel_hpd_clear_and_unblock().
 *
 * Note that the handling of HPD IRQs for another encoder using the same HPD
 * pin as that of @encoder will be also blocked.
 */
void intel_hpd_block(struct intel_encoder *encoder)
{
        struct intel_display *display = to_intel_display(encoder);
        struct intel_hotplug *hotplug = &display->hotplug;
        bool do_flush = false;

        if (encoder->hpd_pin == HPD_NONE)
                return;

        spin_lock_irq(&display->irq.lock);

        if (block_hpd_pin(display, encoder->hpd_pin))
                do_flush = true;

        spin_unlock_irq(&display->irq.lock);

        if (do_flush && hpd_pin_has_pulse(display, encoder->hpd_pin))
                flush_work(&hotplug->dig_port_work);
}

/**
 * intel_hpd_unblock - Unblock handling of HPD IRQs on an HPD pin
 * @encoder: Encoder to unblock the HPD handling for
 *
 * Unblock the handling of HPD IRQs on the HPD pin of @encoder, which was
 * previously blocked by intel_hpd_block(). Any HPD IRQ raised on the
 * HPD pin while it was blocked will be handled for @encoder and for any
 * other encoder sharing the same HPD pin.
 */
void intel_hpd_unblock(struct intel_encoder *encoder)
{
        struct intel_display *display = to_intel_display(encoder);

        if (encoder->hpd_pin == HPD_NONE)
                return;

        spin_lock_irq(&display->irq.lock);

        if (unblock_hpd_pin(display, encoder->hpd_pin))
                queue_work_for_missed_irqs(display);

        spin_unlock_irq(&display->irq.lock);
}

/**
 * intel_hpd_clear_and_unblock - Unblock handling of new HPD IRQs on an HPD pin
 * @encoder: Encoder to unblock the HPD handling for
 *
 * Unblock the handling of HPD IRQs on the HPD pin of @encoder, which was
 * previously blocked by intel_hpd_block(). Any HPD IRQ raised on the
 * HPD pin while it was blocked will be cleared, handling only new IRQs.
 */
void intel_hpd_clear_and_unblock(struct intel_encoder *encoder)
{
        struct intel_display *display = to_intel_display(encoder);
        struct intel_hotplug *hotplug = &display->hotplug;
        enum hpd_pin pin = encoder->hpd_pin;

        if (pin == HPD_NONE)
                return;

        spin_lock_irq(&display->irq.lock);

        if (unblock_hpd_pin(display, pin)) {
                hotplug->event_bits &= ~BIT(pin);
                hotplug->retry_bits &= ~BIT(pin);
                hotplug->short_hpd_pin_mask &= ~BIT(pin);
                hotplug->long_hpd_pin_mask &= ~BIT(pin);
        }

        spin_unlock_irq(&display->irq.lock);
}

void intel_hpd_enable_detection_work(struct intel_display *display)
{
        spin_lock_irq(&display->irq.lock);
        display->hotplug.detection_work_enabled = true;
        queue_work_for_missed_irqs(display);
        spin_unlock_irq(&display->irq.lock);
}

void intel_hpd_disable_detection_work(struct intel_display *display)
{
        spin_lock_irq(&display->irq.lock);
        display->hotplug.detection_work_enabled = false;
        spin_unlock_irq(&display->irq.lock);

        cancel_all_detection_work(display);
}

bool intel_hpd_schedule_detection(struct intel_display *display)
{
        unsigned long flags;
        bool ret;

        spin_lock_irqsave(&display->irq.lock, flags);
        ret = queue_delayed_detection_work(display, &display->hotplug.hotplug_work, 0);
        spin_unlock_irqrestore(&display->irq.lock, flags);

        return ret;
}

static int i915_hpd_storm_ctl_show(struct seq_file *m, void *data)
{
        struct intel_display *display = m->private;
        struct intel_hotplug *hotplug = &display->hotplug;

        /* Synchronize with everything first in case there's been an HPD
         * storm, but we haven't finished handling it in the kernel yet
         */
        intel_parent_irq_synchronize(display);
        flush_work(&display->hotplug.dig_port_work);
        flush_delayed_work(&display->hotplug.hotplug_work);

        seq_printf(m, "Threshold: %d\n", hotplug->hpd_storm_threshold);
        seq_printf(m, "Detected: %s\n",
                   str_yes_no(delayed_work_pending(&hotplug->reenable_work)));

        return 0;
}

static ssize_t i915_hpd_storm_ctl_write(struct file *file,
                                        const char __user *ubuf, size_t len,
                                        loff_t *offp)
{
        struct seq_file *m = file->private_data;
        struct intel_display *display = m->private;
        struct intel_hotplug *hotplug = &display->hotplug;
        unsigned int new_threshold;
        int i;
        char *newline;
        char tmp[16];

        if (len >= sizeof(tmp))
                return -EINVAL;

        if (copy_from_user(tmp, ubuf, len))
                return -EFAULT;

        tmp[len] = '\0';

        /* Strip newline, if any */
        newline = strchr(tmp, '\n');
        if (newline)
                *newline = '\0';

        if (strcmp(tmp, "reset") == 0)
                new_threshold = HPD_STORM_DEFAULT_THRESHOLD;
        else if (kstrtouint(tmp, 10, &new_threshold) != 0)
                return -EINVAL;

        if (new_threshold > 0)
                drm_dbg_kms(display->drm,
                            "Setting HPD storm detection threshold to %d\n",
                            new_threshold);
        else
                drm_dbg_kms(display->drm, "Disabling HPD storm detection\n");

        spin_lock_irq(&display->irq.lock);
        hotplug->hpd_storm_threshold = new_threshold;
        /* Reset the HPD storm stats so we don't accidentally trigger a storm */
        for_each_hpd_pin(i)
                hotplug->stats[i].count = 0;
        spin_unlock_irq(&display->irq.lock);

        /* Re-enable hpd immediately if we were in an irq storm */
        flush_delayed_work(&display->hotplug.reenable_work);

        return len;
}

static int i915_hpd_storm_ctl_open(struct inode *inode, struct file *file)
{
        return single_open(file, i915_hpd_storm_ctl_show, inode->i_private);
}

static const struct file_operations i915_hpd_storm_ctl_fops = {
        .owner = THIS_MODULE,
        .open = i915_hpd_storm_ctl_open,
        .read = seq_read,
        .llseek = seq_lseek,
        .release = single_release,
        .write = i915_hpd_storm_ctl_write
};

static int i915_hpd_short_storm_ctl_show(struct seq_file *m, void *data)
{
        struct intel_display *display = m->private;

        seq_printf(m, "Enabled: %s\n",
                   str_yes_no(display->hotplug.hpd_short_storm_enabled));

        return 0;
}

static int
i915_hpd_short_storm_ctl_open(struct inode *inode, struct file *file)
{
        return single_open(file, i915_hpd_short_storm_ctl_show,
                           inode->i_private);
}

static ssize_t i915_hpd_short_storm_ctl_write(struct file *file,
                                              const char __user *ubuf,
                                              size_t len, loff_t *offp)
{
        struct seq_file *m = file->private_data;
        struct intel_display *display = m->private;
        struct intel_hotplug *hotplug = &display->hotplug;
        char *newline;
        char tmp[16];
        int i;
        bool new_state;

        if (len >= sizeof(tmp))
                return -EINVAL;

        if (copy_from_user(tmp, ubuf, len))
                return -EFAULT;

        tmp[len] = '\0';

        /* Strip newline, if any */
        newline = strchr(tmp, '\n');
        if (newline)
                *newline = '\0';

        /* Reset to the "default" state for this system */
        if (strcmp(tmp, "reset") == 0)
                new_state = !HAS_DP_MST(display);
        else if (kstrtobool(tmp, &new_state) != 0)
                return -EINVAL;

        drm_dbg_kms(display->drm, "%sabling HPD short storm detection\n",
                    new_state ? "En" : "Dis");

        spin_lock_irq(&display->irq.lock);
        hotplug->hpd_short_storm_enabled = new_state;
        /* Reset the HPD storm stats so we don't accidentally trigger a storm */
        for_each_hpd_pin(i)
                hotplug->stats[i].count = 0;
        spin_unlock_irq(&display->irq.lock);

        /* Re-enable hpd immediately if we were in an irq storm */
        flush_delayed_work(&display->hotplug.reenable_work);

        return len;
}

static const struct file_operations i915_hpd_short_storm_ctl_fops = {
        .owner = THIS_MODULE,
        .open = i915_hpd_short_storm_ctl_open,
        .read = seq_read,
        .llseek = seq_lseek,
        .release = single_release,
        .write = i915_hpd_short_storm_ctl_write,
};

void intel_hpd_debugfs_register(struct intel_display *display)
{
        struct dentry *debugfs_root = display->drm->debugfs_root;

        debugfs_create_file("i915_hpd_storm_ctl", 0644, debugfs_root,
                            display, &i915_hpd_storm_ctl_fops);
        debugfs_create_file("i915_hpd_short_storm_ctl", 0644, debugfs_root,
                            display, &i915_hpd_short_storm_ctl_fops);
        debugfs_create_bool("i915_ignore_long_hpd", 0644, debugfs_root,
                            &display->hotplug.ignore_long_hpd);
}