// SPDX-License-Identifier: (GPL-2.0 OR BSD-3-Clause)
/*
 * Copyright(c) 2019 Intel Corporation.
 *
 */

#include "aspm.h"

/* Time after which the timer interrupt will re-enable ASPM */
#define ASPM_TIMER_MS 1000
/* Time for which interrupts are ignored after a timer has been scheduled */
#define ASPM_RESCHED_TIMER_MS (ASPM_TIMER_MS / 2)
/* Two interrupts within this time trigger ASPM disable */
#define ASPM_TRIGGER_MS 1
#define ASPM_TRIGGER_NS (ASPM_TRIGGER_MS * 1000 * 1000ull)
#define ASPM_L1_SUPPORTED(reg) \
        ((((reg) & PCI_EXP_LNKCAP_ASPMS) >> 10) & 0x2)

uint aspm_mode = ASPM_MODE_DISABLED;
module_param_named(aspm, aspm_mode, uint, 0444);
MODULE_PARM_DESC(aspm, "PCIe ASPM: 0: disable, 1: enable, 2: dynamic");

static bool aspm_hw_l1_supported(struct hfi1_devdata *dd)
{
        struct pci_dev *parent = dd->pcidev->bus->self;
        u32 up, dn;

        /*
         * If the driver does not have access to the upstream component,
         * it cannot support ASPM L1 at all.
         */
        if (!parent)
                return false;

        pcie_capability_read_dword(dd->pcidev, PCI_EXP_LNKCAP, &dn);
        dn = ASPM_L1_SUPPORTED(dn);

        pcie_capability_read_dword(parent, PCI_EXP_LNKCAP, &up);
        up = ASPM_L1_SUPPORTED(up);

        /* ASPM works on A-step but is reported as not supported */
        return (!!dn || is_ax(dd)) && !!up;
}

/* Set L1 entrance latency for slower entry to L1 */
static void aspm_hw_set_l1_ent_latency(struct hfi1_devdata *dd)
{
        u32 l1_ent_lat = 0x4u;
        u32 reg32;

        pci_read_config_dword(dd->pcidev, PCIE_CFG_REG_PL3, &reg32);
        reg32 &= ~PCIE_CFG_REG_PL3_L1_ENT_LATENCY_SMASK;
        reg32 |= l1_ent_lat << PCIE_CFG_REG_PL3_L1_ENT_LATENCY_SHIFT;
        pci_write_config_dword(dd->pcidev, PCIE_CFG_REG_PL3, reg32);
}

static void aspm_hw_enable_l1(struct hfi1_devdata *dd)
{
        struct pci_dev *parent = dd->pcidev->bus->self;

        /*
         * If the driver does not have access to the upstream component,
         * it cannot support ASPM L1 at all.
         */
        if (!parent)
                return;

        /* Enable ASPM L1 first in upstream component and then downstream */
        pcie_capability_clear_and_set_word(parent, PCI_EXP_LNKCTL,
                                           PCI_EXP_LNKCTL_ASPMC,
                                           PCI_EXP_LNKCTL_ASPM_L1);
        pcie_capability_clear_and_set_word(dd->pcidev, PCI_EXP_LNKCTL,
                                           PCI_EXP_LNKCTL_ASPMC,
                                           PCI_EXP_LNKCTL_ASPM_L1);
}

void aspm_hw_disable_l1(struct hfi1_devdata *dd)
{
        struct pci_dev *parent = dd->pcidev->bus->self;

        /* Disable ASPM L1 first in downstream component and then upstream */
        pcie_capability_clear_and_set_word(dd->pcidev, PCI_EXP_LNKCTL,
                                           PCI_EXP_LNKCTL_ASPMC, 0x0);
        if (parent)
                pcie_capability_clear_and_set_word(parent, PCI_EXP_LNKCTL,
                                                   PCI_EXP_LNKCTL_ASPMC, 0x0);
}

static  void aspm_enable(struct hfi1_devdata *dd)
{
        if (dd->aspm_enabled || aspm_mode == ASPM_MODE_DISABLED ||
            !dd->aspm_supported)
                return;

        aspm_hw_enable_l1(dd);
        dd->aspm_enabled = true;
}

static  void aspm_disable(struct hfi1_devdata *dd)
{
        if (!dd->aspm_enabled || aspm_mode == ASPM_MODE_ENABLED)
                return;

        aspm_hw_disable_l1(dd);
        dd->aspm_enabled = false;
}

static  void aspm_disable_inc(struct hfi1_devdata *dd)
{
        unsigned long flags;

        spin_lock_irqsave(&dd->aspm_lock, flags);
        aspm_disable(dd);
        atomic_inc(&dd->aspm_disabled_cnt);
        spin_unlock_irqrestore(&dd->aspm_lock, flags);
}

static  void aspm_enable_dec(struct hfi1_devdata *dd)
{
        unsigned long flags;

        spin_lock_irqsave(&dd->aspm_lock, flags);
        if (atomic_dec_and_test(&dd->aspm_disabled_cnt))
                aspm_enable(dd);
        spin_unlock_irqrestore(&dd->aspm_lock, flags);
}

/* ASPM processing for each receive context interrupt */
void __aspm_ctx_disable(struct hfi1_ctxtdata *rcd)
{
        bool restart_timer;
        bool close_interrupts;
        unsigned long flags;
        ktime_t now, prev;

        spin_lock_irqsave(&rcd->aspm_lock, flags);
        /* PSM contexts are open */
        if (!rcd->aspm_intr_enable)
                goto unlock;

        prev = rcd->aspm_ts_last_intr;
        now = ktime_get();
        rcd->aspm_ts_last_intr = now;

        /* An interrupt pair close together in time */
        close_interrupts = ktime_to_ns(ktime_sub(now, prev)) < ASPM_TRIGGER_NS;

        /* Don't push out our timer till this much time has elapsed */
        restart_timer = ktime_to_ns(ktime_sub(now, rcd->aspm_ts_timer_sched)) >
                                    ASPM_RESCHED_TIMER_MS * NSEC_PER_MSEC;
        restart_timer = restart_timer && close_interrupts;

        /* Disable ASPM and schedule timer */
        if (rcd->aspm_enabled && close_interrupts) {
                aspm_disable_inc(rcd->dd);
                rcd->aspm_enabled = false;
                restart_timer = true;
        }

        if (restart_timer) {
                mod_timer(&rcd->aspm_timer,
                          jiffies + msecs_to_jiffies(ASPM_TIMER_MS));
                rcd->aspm_ts_timer_sched = now;
        }
unlock:
        spin_unlock_irqrestore(&rcd->aspm_lock, flags);
}

/* Timer function for re-enabling ASPM in the absence of interrupt activity */
static  void aspm_ctx_timer_function(struct timer_list *t)
{
        struct hfi1_ctxtdata *rcd = from_timer(rcd, t, aspm_timer);
        unsigned long flags;

        spin_lock_irqsave(&rcd->aspm_lock, flags);
        aspm_enable_dec(rcd->dd);
        rcd->aspm_enabled = true;
        spin_unlock_irqrestore(&rcd->aspm_lock, flags);
}

/*
 * Disable interrupt processing for verbs contexts when PSM or VNIC contexts
 * are open.
 */
void aspm_disable_all(struct hfi1_devdata *dd)
{
        struct hfi1_ctxtdata *rcd;
        unsigned long flags;
        u16 i;

        for (i = 0; i < dd->first_dyn_alloc_ctxt; i++) {
                rcd = hfi1_rcd_get_by_index(dd, i);
                if (rcd) {
                        del_timer_sync(&rcd->aspm_timer);
                        spin_lock_irqsave(&rcd->aspm_lock, flags);
                        rcd->aspm_intr_enable = false;
                        spin_unlock_irqrestore(&rcd->aspm_lock, flags);
                        hfi1_rcd_put(rcd);
                }
        }

        aspm_disable(dd);
        atomic_set(&dd->aspm_disabled_cnt, 0);
}

/* Re-enable interrupt processing for verbs contexts */
void aspm_enable_all(struct hfi1_devdata *dd)
{
        struct hfi1_ctxtdata *rcd;
        unsigned long flags;
        u16 i;

        aspm_enable(dd);

        if (aspm_mode != ASPM_MODE_DYNAMIC)
                return;

        for (i = 0; i < dd->first_dyn_alloc_ctxt; i++) {
                rcd = hfi1_rcd_get_by_index(dd, i);
                if (rcd) {
                        spin_lock_irqsave(&rcd->aspm_lock, flags);
                        rcd->aspm_intr_enable = true;
                        rcd->aspm_enabled = true;
                        spin_unlock_irqrestore(&rcd->aspm_lock, flags);
                        hfi1_rcd_put(rcd);
                }
        }
}

static  void aspm_ctx_init(struct hfi1_ctxtdata *rcd)
{
        spin_lock_init(&rcd->aspm_lock);
        timer_setup(&rcd->aspm_timer, aspm_ctx_timer_function, 0);
        rcd->aspm_intr_supported = rcd->dd->aspm_supported &&
                aspm_mode == ASPM_MODE_DYNAMIC &&
                rcd->ctxt < rcd->dd->first_dyn_alloc_ctxt;
}

void aspm_init(struct hfi1_devdata *dd)
{
        struct hfi1_ctxtdata *rcd;
        u16 i;

        spin_lock_init(&dd->aspm_lock);
        dd->aspm_supported = aspm_hw_l1_supported(dd);

        for (i = 0; i < dd->first_dyn_alloc_ctxt; i++) {
                rcd = hfi1_rcd_get_by_index(dd, i);
                if (rcd)
                        aspm_ctx_init(rcd);
                hfi1_rcd_put(rcd);
        }

        /* Start with ASPM disabled */
        aspm_hw_set_l1_ent_latency(dd);
        dd->aspm_enabled = false;
        aspm_hw_disable_l1(dd);

        /* Now turn on ASPM if configured */
        aspm_enable_all(dd);
}

void aspm_exit(struct hfi1_devdata *dd)
{
        aspm_disable_all(dd);

        /* Turn on ASPM on exit to conserve power */
        aspm_enable(dd);
}