/*
 * This file is subject to the terms and conditions of the GNU General Public
 * License.  See the file "COPYING" in the main directory of this archive
 * for more details.
 *
 * Copyright (C) 2004, 2005 MIPS Technologies, Inc.  All rights reserved.
 * Copyright (C) 2013 Imagination Technologies Ltd.
 */
#include <linux/kernel.h>
#include <linux/device.h>
#include <linux/fs.h>
#include <linux/slab.h>
#include <linux/export.h>

#include <asm/mipsregs.h>
#include <asm/mipsmtregs.h>
#include <asm/mips_mt.h>
#include <asm/vpe.h>

static int major;

/* The number of TCs and VPEs physically available on the core */
static int hw_tcs, hw_vpes;

/* We are prepared so configure and start the VPE... */
int vpe_run(struct vpe *v)
{
        unsigned long flags, val, dmt_flag;
        struct vpe_notifications *notifier;
        unsigned int vpeflags;
        struct tc *t;

        /* check we are the Master VPE */
        local_irq_save(flags);
        val = read_c0_vpeconf0();
        if (!(val & VPECONF0_MVP)) {
                pr_warn("VPE loader: only Master VPE's are able to config MT\n");
                local_irq_restore(flags);

                return -1;
        }

        dmt_flag = dmt();
        vpeflags = dvpe();

        if (list_empty(&v->tc)) {
                evpe(vpeflags);
                emt(dmt_flag);
                local_irq_restore(flags);

                pr_warn("VPE loader: No TC's associated with VPE %d\n",
                        v->minor);

                return -ENOEXEC;
        }

        t = list_first_entry(&v->tc, struct tc, tc);

        /* Put MVPE's into 'configuration state' */
        set_c0_mvpcontrol(MVPCONTROL_VPC);

        settc(t->index);

        /* should check it is halted, and not activated */
        if ((read_tc_c0_tcstatus() & TCSTATUS_A) ||
           !(read_tc_c0_tchalt() & TCHALT_H)) {
                evpe(vpeflags);
                emt(dmt_flag);
                local_irq_restore(flags);

                pr_warn("VPE loader: TC %d is already active!\n",
                        t->index);

                return -ENOEXEC;
        }

        /*
         * Write the address we want it to start running from in the TCPC
         * register.
         */
        write_tc_c0_tcrestart((unsigned long)v->__start);
        write_tc_c0_tccontext((unsigned long)0);

        /*
         * Mark the TC as activated, not interrupt exempt and not dynamically
         * allocatable
         */
        val = read_tc_c0_tcstatus();
        val = (val & ~(TCSTATUS_DA | TCSTATUS_IXMT)) | TCSTATUS_A;
        write_tc_c0_tcstatus(val);

        write_tc_c0_tchalt(read_tc_c0_tchalt() & ~TCHALT_H);

        /*
         * The sde-kit passes 'memsize' to __start in $a3, so set something
         * here...  Or set $a3 to zero and define DFLT_STACK_SIZE and
         * DFLT_HEAP_SIZE when you compile your program
         */
        mttgpr(6, v->ntcs);
        mttgpr(7, physical_memsize);

        /* set up VPE1 */
        /*
         * bind the TC to VPE 1 as late as possible so we only have the final
         * VPE registers to set up, and so an EJTAG probe can trigger on it
         */
        write_tc_c0_tcbind((read_tc_c0_tcbind() & ~TCBIND_CURVPE) | 1);

        write_vpe_c0_vpeconf0(read_vpe_c0_vpeconf0() & ~(VPECONF0_VPA));

        back_to_back_c0_hazard();

        /* Set up the XTC bit in vpeconf0 to point at our tc */
        write_vpe_c0_vpeconf0((read_vpe_c0_vpeconf0() & ~(VPECONF0_XTC))
                              | (t->index << VPECONF0_XTC_SHIFT));

        back_to_back_c0_hazard();

        /* enable this VPE */
        write_vpe_c0_vpeconf0(read_vpe_c0_vpeconf0() | VPECONF0_VPA);

        /* clear out any left overs from a previous program */
        write_vpe_c0_status(0);
        write_vpe_c0_cause(0);

        /* take system out of configuration state */
        clear_c0_mvpcontrol(MVPCONTROL_VPC);

        /*
         * SMTC/SMVP kernels manage VPE enable independently,
         * but uniprocessor kernels need to turn it on, even
         * if that wasn't the pre-dvpe() state.
         */
#ifdef CONFIG_SMP
        evpe(vpeflags);
#else
        evpe(EVPE_ENABLE);
#endif
        emt(dmt_flag);
        local_irq_restore(flags);

        list_for_each_entry(notifier, &v->notify, list)
                notifier->start(VPE_MODULE_MINOR);

        return 0;
}

void cleanup_tc(struct tc *tc)
{
        unsigned long flags;
        unsigned int mtflags, vpflags;
        int tmp;

        local_irq_save(flags);
        mtflags = dmt();
        vpflags = dvpe();
        /* Put MVPE's into 'configuration state' */
        set_c0_mvpcontrol(MVPCONTROL_VPC);

        settc(tc->index);
        tmp = read_tc_c0_tcstatus();

        /* mark not allocated and not dynamically allocatable */
        tmp &= ~(TCSTATUS_A | TCSTATUS_DA);
        tmp |= TCSTATUS_IXMT;   /* interrupt exempt */
        write_tc_c0_tcstatus(tmp);

        write_tc_c0_tchalt(TCHALT_H);
        mips_ihb();

        clear_c0_mvpcontrol(MVPCONTROL_VPC);
        evpe(vpflags);
        emt(mtflags);
        local_irq_restore(flags);
}

/* module wrapper entry points */
/* give me a vpe */
void *vpe_alloc(void)
{
        int i;
        struct vpe *v;

        /* find a vpe */
        for (i = 1; i < MAX_VPES; i++) {
                v = get_vpe(i);
                if (v != NULL) {
                        v->state = VPE_STATE_INUSE;
                        return v;
                }
        }
        return NULL;
}
EXPORT_SYMBOL(vpe_alloc);

/* start running from here */
int vpe_start(void *vpe, unsigned long start)
{
        struct vpe *v = vpe;

        v->__start = start;
        return vpe_run(v);
}
EXPORT_SYMBOL(vpe_start);

/* halt it for now */
int vpe_stop(void *vpe)
{
        struct vpe *v = vpe;
        struct tc *t;
        unsigned int evpe_flags;

        evpe_flags = dvpe();

        t = list_entry(v->tc.next, struct tc, tc);
        if (t != NULL) {
                settc(t->index);
                write_vpe_c0_vpeconf0(read_vpe_c0_vpeconf0() & ~VPECONF0_VPA);
        }

        evpe(evpe_flags);

        return 0;
}
EXPORT_SYMBOL(vpe_stop);

/* I've done with it thank you */
int vpe_free(void *vpe)
{
        struct vpe *v = vpe;
        struct tc *t;
        unsigned int evpe_flags;

        t = list_entry(v->tc.next, struct tc, tc);
        if (t == NULL)
                return -ENOEXEC;

        evpe_flags = dvpe();

        /* Put MVPE's into 'configuration state' */
        set_c0_mvpcontrol(MVPCONTROL_VPC);

        settc(t->index);
        write_vpe_c0_vpeconf0(read_vpe_c0_vpeconf0() & ~VPECONF0_VPA);

        /* halt the TC */
        write_tc_c0_tchalt(TCHALT_H);
        mips_ihb();

        /* mark the TC unallocated */
        write_tc_c0_tcstatus(read_tc_c0_tcstatus() & ~TCSTATUS_A);

        v->state = VPE_STATE_UNUSED;

        clear_c0_mvpcontrol(MVPCONTROL_VPC);
        evpe(evpe_flags);

        return 0;
}
EXPORT_SYMBOL(vpe_free);

static ssize_t store_kill(struct device *dev, struct device_attribute *attr,
                          const char *buf, size_t len)
{
        struct vpe *vpe = get_vpe(aprp_cpu_index());
        struct vpe_notifications *notifier;

        list_for_each_entry(notifier, &vpe->notify, list)
                notifier->stop(aprp_cpu_index());

        release_progmem(vpe->load_addr);
        cleanup_tc(get_tc(aprp_cpu_index()));
        vpe_stop(vpe);
        vpe_free(vpe);

        return len;
}
static DEVICE_ATTR(kill, S_IWUSR, NULL, store_kill);

static ssize_t ntcs_show(struct device *cd, struct device_attribute *attr,
                         char *buf)
{
        struct vpe *vpe = get_vpe(aprp_cpu_index());

        return sprintf(buf, "%d\n", vpe->ntcs);
}

static ssize_t ntcs_store(struct device *dev, struct device_attribute *attr,
                          const char *buf, size_t len)
{
        struct vpe *vpe = get_vpe(aprp_cpu_index());
        unsigned long new;
        int ret;

        ret = kstrtoul(buf, 0, &new);
        if (ret < 0)
                return ret;

        if (new == 0 || new > (hw_tcs - aprp_cpu_index()))
                return -EINVAL;

        vpe->ntcs = new;

        return len;
}
static DEVICE_ATTR_RW(ntcs);

static struct attribute *vpe_attrs[] = {
        &dev_attr_kill.attr,
        &dev_attr_ntcs.attr,
        NULL,
};
ATTRIBUTE_GROUPS(vpe);

static void vpe_device_release(struct device *cd)
{
        kfree(cd);
}

static struct class vpe_class = {
        .name = "vpe",
        .owner = THIS_MODULE,
        .dev_release = vpe_device_release,
        .dev_groups = vpe_groups,
};

static struct device vpe_device;

int __init vpe_module_init(void)
{
        unsigned int mtflags, vpflags;
        unsigned long flags, val;
        struct vpe *v = NULL;
        struct tc *t;
        int tc, err;

        if (!cpu_has_mipsmt) {
                pr_warn("VPE loader: not a MIPS MT capable processor\n");
                return -ENODEV;
        }

        if (vpelimit == 0) {
                pr_warn("No VPEs reserved for AP/SP, not initialize VPE loader\n"
                        "Pass maxvpes=<n> argument as kernel argument\n");

                return -ENODEV;
        }

        if (aprp_cpu_index() == 0) {
                pr_warn("No TCs reserved for AP/SP, not initialize VPE loader\n"
                        "Pass maxtcs=<n> argument as kernel argument\n");

                return -ENODEV;
        }

        major = register_chrdev(0, VPE_MODULE_NAME, &vpe_fops);
        if (major < 0) {
                pr_warn("VPE loader: unable to register character device\n");
                return major;
        }

        err = class_register(&vpe_class);
        if (err) {
                pr_err("vpe_class registration failed\n");
                goto out_chrdev;
        }

        device_initialize(&vpe_device);
        vpe_device.class        = &vpe_class,
        vpe_device.parent       = NULL,
        dev_set_name(&vpe_device, "vpe1");
        vpe_device.devt = MKDEV(major, VPE_MODULE_MINOR);
        err = device_add(&vpe_device);
        if (err) {
                pr_err("Adding vpe_device failed\n");
                goto out_class;
        }

        local_irq_save(flags);
        mtflags = dmt();
        vpflags = dvpe();

        /* Put MVPE's into 'configuration state' */
        set_c0_mvpcontrol(MVPCONTROL_VPC);

        val = read_c0_mvpconf0();
        hw_tcs = (val & MVPCONF0_PTC) + 1;
        hw_vpes = ((val & MVPCONF0_PVPE) >> MVPCONF0_PVPE_SHIFT) + 1;

        for (tc = aprp_cpu_index(); tc < hw_tcs; tc++) {
                /*
                 * Must re-enable multithreading temporarily or in case we
                 * reschedule send IPIs or similar we might hang.
                 */
                clear_c0_mvpcontrol(MVPCONTROL_VPC);
                evpe(vpflags);
                emt(mtflags);
                local_irq_restore(flags);
                t = alloc_tc(tc);
                if (!t) {
                        err = -ENOMEM;
                        goto out_dev;
                }

                local_irq_save(flags);
                mtflags = dmt();
                vpflags = dvpe();
                set_c0_mvpcontrol(MVPCONTROL_VPC);

                /* VPE's */
                if (tc < hw_tcs) {
                        settc(tc);

                        v = alloc_vpe(tc);
                        if (v == NULL) {
                                pr_warn("VPE: unable to allocate VPE\n");
                                goto out_reenable;
                        }

                        v->ntcs = hw_tcs - aprp_cpu_index();

                        /* add the tc to the list of this vpe's tc's. */
                        list_add(&t->tc, &v->tc);

                        /* deactivate all but vpe0 */
                        if (tc >= aprp_cpu_index()) {
                                unsigned long tmp = read_vpe_c0_vpeconf0();

                                tmp &= ~VPECONF0_VPA;

                                /* master VPE */
                                tmp |= VPECONF0_MVP;
                                write_vpe_c0_vpeconf0(tmp);
                        }

                        /* disable multi-threading with TC's */
                        write_vpe_c0_vpecontrol(read_vpe_c0_vpecontrol() &
                                                ~VPECONTROL_TE);

                        if (tc >= vpelimit) {
                                /*
                                 * Set config to be the same as vpe0,
                                 * particularly kseg0 coherency alg
                                 */
                                write_vpe_c0_config(read_c0_config());
                        }
                }

                /* TC's */
                t->pvpe = v;    /* set the parent vpe */

                if (tc >= aprp_cpu_index()) {
                        unsigned long tmp;

                        settc(tc);

                        /* Any TC that is bound to VPE0 gets left as is - in
                         * case we are running SMTC on VPE0. A TC that is bound
                         * to any other VPE gets bound to VPE0, ideally I'd like
                         * to make it homeless but it doesn't appear to let me
                         * bind a TC to a non-existent VPE. Which is perfectly
                         * reasonable.
                         *
                         * The (un)bound state is visible to an EJTAG probe so
                         * may notify GDB...
                         */
                        tmp = read_tc_c0_tcbind();
                        if (tmp & TCBIND_CURVPE) {
                                /* tc is bound >vpe0 */
                                write_tc_c0_tcbind(tmp & ~TCBIND_CURVPE);

                                t->pvpe = get_vpe(0);   /* set the parent vpe */
                        }

                        /* halt the TC */
                        write_tc_c0_tchalt(TCHALT_H);
                        mips_ihb();

                        tmp = read_tc_c0_tcstatus();

                        /* mark not activated and not dynamically allocatable */
                        tmp &= ~(TCSTATUS_A | TCSTATUS_DA);
                        tmp |= TCSTATUS_IXMT;   /* interrupt exempt */
                        write_tc_c0_tcstatus(tmp);
                }
        }

out_reenable:
        /* release config state */
        clear_c0_mvpcontrol(MVPCONTROL_VPC);

        evpe(vpflags);
        emt(mtflags);
        local_irq_restore(flags);

        return 0;

out_dev:
        device_del(&vpe_device);

out_class:
        class_unregister(&vpe_class);

out_chrdev:
        unregister_chrdev(major, VPE_MODULE_NAME);

        return err;
}

void __exit vpe_module_exit(void)
{
        struct vpe *v, *n;

        device_del(&vpe_device);
        class_unregister(&vpe_class);
        unregister_chrdev(major, VPE_MODULE_NAME);

        /* No locking needed here */
        list_for_each_entry_safe(v, n, &vpecontrol.vpe_list, list) {
                if (v->state != VPE_STATE_UNUSED)
                        release_vpe(v);
        }
}