// SPDX-License-Identifier: GPL-2.0
/*
 * Setup routines for AGP 3.5 compliant bridges.
 */

#include <linux/list.h>
#include <linux/pci.h>
#include <linux/agp_backend.h>
#include <linux/module.h>
#include <linux/slab.h>

#include "agp.h"

/* Generic AGP 3.5 enabling routines */

struct agp_3_5_dev {
        struct list_head list;
        u8 capndx;
        u32 maxbw;
        struct pci_dev *dev;
};

static void agp_3_5_dev_list_insert(struct list_head *head, struct list_head *new)
{
        struct agp_3_5_dev *cur, *n = list_entry(new, struct agp_3_5_dev, list);
        struct list_head *pos;

        list_for_each(pos, head) {
                cur = list_entry(pos, struct agp_3_5_dev, list);
                if (cur->maxbw > n->maxbw)
                        break;
        }
        list_add_tail(new, pos);
}

static void agp_3_5_dev_list_sort(struct agp_3_5_dev *list, unsigned int ndevs)
{
        struct agp_3_5_dev *cur;
        struct pci_dev *dev;
        struct list_head *pos, *tmp, *head = &list->list, *start = head->next;
        u32 nistat;

        INIT_LIST_HEAD(head);

        for (pos=start; pos!=head; ) {
                cur = list_entry(pos, struct agp_3_5_dev, list);
                dev = cur->dev;

                pci_read_config_dword(dev, cur->capndx+AGPNISTAT, &nistat);
                cur->maxbw = (nistat >> 16) & 0xff;

                tmp = pos;
                pos = pos->next;
                agp_3_5_dev_list_insert(head, tmp);
        }
}

/*
 * Initialize all isochronous transfer parameters for an AGP 3.0
 * node (i.e. a host bridge in combination with the adapters
 * lying behind it...)
 */

static int agp_3_5_isochronous_node_enable(struct agp_bridge_data *bridge,
                struct agp_3_5_dev *dev_list, unsigned int ndevs)
{
        /*
         * Convenience structure to make the calculations clearer
         * here.  The field names come straight from the AGP 3.0 spec.
         */
        struct isoch_data {
                u32 maxbw;
                u32 n;
                u32 y;
                u32 l;
                u32 rq;
                struct agp_3_5_dev *dev;
        };

        struct pci_dev *td = bridge->dev, *dev;
        struct list_head *head = &dev_list->list, *pos;
        struct agp_3_5_dev *cur;
        struct isoch_data *master, target;
        unsigned int cdev = 0;
        u32 mnistat, tnistat, tstatus, mcmd;
        u16 tnicmd, mnicmd;
        u32 tot_bw = 0, tot_n = 0, tot_rq = 0, y_max, rq_isoch, rq_async;
        u32 step, rem, rem_isoch, rem_async;
        int ret = 0;

        /*
         * We'll work with an array of isoch_data's (one for each
         * device in dev_list) throughout this function.
         */
        master = kmalloc_array(ndevs, sizeof(*master), GFP_KERNEL);
        if (master == NULL) {
                ret = -ENOMEM;
                goto get_out;
        }

        /*
         * Sort the device list by maxbw.  We need to do this because the
         * spec suggests that the devices with the smallest requirements
         * have their resources allocated first, with all remaining resources
         * falling to the device with the largest requirement.
         *
         * We don't exactly do this, we divide target resources by ndevs
         * and split them amongst the AGP 3.0 devices.  The remainder of such
         * division operations are dropped on the last device, sort of like
         * the spec mentions it should be done.
         *
         * We can't do this sort when we initially construct the dev_list
         * because we don't know until this function whether isochronous
         * transfers are enabled and consequently whether maxbw will mean
         * anything.
         */
        agp_3_5_dev_list_sort(dev_list, ndevs);

        pci_read_config_dword(td, bridge->capndx+AGPNISTAT, &tnistat);
        pci_read_config_dword(td, bridge->capndx+AGPSTAT, &tstatus);

        /* Extract power-on defaults from the target */
        target.maxbw = (tnistat >> 16) & 0xff;
        target.n     = (tnistat >> 8)  & 0xff;
        target.y     = (tnistat >> 6)  & 0x3;
        target.l     = (tnistat >> 3)  & 0x7;
        target.rq    = (tstatus >> 24) & 0xff;

        y_max = target.y;

        /*
         * Extract power-on defaults for each device in dev_list.  Along
         * the way, calculate the total isochronous bandwidth required
         * by these devices and the largest requested payload size.
         */
        list_for_each(pos, head) {
                cur = list_entry(pos, struct agp_3_5_dev, list);
                dev = cur->dev;

                pci_read_config_dword(dev, cur->capndx+AGPNISTAT, &mnistat);

                master[cdev].maxbw = (mnistat >> 16) & 0xff;
                master[cdev].n     = (mnistat >> 8)  & 0xff;
                master[cdev].y     = (mnistat >> 6)  & 0x3;
                master[cdev].dev   = cur;

                tot_bw += master[cdev].maxbw;
                y_max = max(y_max, master[cdev].y);

                cdev++;
        }

        /* Check if this configuration has any chance of working */
        if (tot_bw > target.maxbw) {
                dev_err(&td->dev, "isochronous bandwidth required "
                        "by AGP 3.0 devices exceeds that which is supported by "
                        "the AGP 3.0 bridge!\n");
                ret = -ENODEV;
                goto free_and_exit;
        }

        target.y = y_max;

        /*
         * Write the calculated payload size into the target's NICMD
         * register.  Doing this directly effects the ISOCH_N value
         * in the target's NISTAT register, so we need to do this now
         * to get an accurate value for ISOCH_N later.
         */
        pci_read_config_word(td, bridge->capndx+AGPNICMD, &tnicmd);
        tnicmd &= ~(0x3 << 6);
        tnicmd |= target.y << 6;
        pci_write_config_word(td, bridge->capndx+AGPNICMD, tnicmd);

        /* Reread the target's ISOCH_N */
        pci_read_config_dword(td, bridge->capndx+AGPNISTAT, &tnistat);
        target.n = (tnistat >> 8) & 0xff;

        /* Calculate the minimum ISOCH_N needed by each master */
        for (cdev=0; cdev<ndevs; cdev++) {
                master[cdev].y = target.y;
                master[cdev].n = master[cdev].maxbw / (master[cdev].y + 1);

                tot_n += master[cdev].n;
        }

        /* Exit if the minimal ISOCH_N allocation among the masters is more
         * than the target can handle. */
        if (tot_n > target.n) {
                dev_err(&td->dev, "number of isochronous "
                        "transactions per period required by AGP 3.0 devices "
                        "exceeds that which is supported by the AGP 3.0 "
                        "bridge!\n");
                ret = -ENODEV;
                goto free_and_exit;
        }

        /* Calculate left over ISOCH_N capability in the target.  We'll give
         * this to the hungriest device (as per the spec) */
        rem  = target.n - tot_n;

        /*
         * Calculate the minimum isochronous RQ depth needed by each master.
         * Along the way, distribute the extra ISOCH_N capability calculated
         * above.
         */
        for (cdev=0; cdev<ndevs; cdev++) {
                /*
                 * This is a little subtle.  If ISOCH_Y > 64B, then ISOCH_Y
                 * byte isochronous writes will be broken into 64B pieces.
                 * This means we need to budget more RQ depth to account for
                 * these kind of writes (each isochronous write is actually
                 * many writes on the AGP bus).
                 */
                master[cdev].rq = master[cdev].n;
                if (master[cdev].y > 0x1)
                        master[cdev].rq *= (1 << (master[cdev].y - 1));

                tot_rq += master[cdev].rq;
        }
        master[ndevs-1].n += rem;

        /* Figure the number of isochronous and asynchronous RQ slots the
         * target is providing. */
        rq_isoch = (target.y > 0x1) ? target.n * (1 << (target.y - 1)) : target.n;
        rq_async = target.rq - rq_isoch;

        /* Exit if the minimal RQ needs of the masters exceeds what the target
         * can provide. */
        if (tot_rq > rq_isoch) {
                dev_err(&td->dev, "number of request queue slots "
                        "required by the isochronous bandwidth requested by "
                        "AGP 3.0 devices exceeds the number provided by the "
                        "AGP 3.0 bridge!\n");
                ret = -ENODEV;
                goto free_and_exit;
        }

        /* Calculate asynchronous RQ capability in the target (per master) as
         * well as the total number of leftover isochronous RQ slots. */
        step      = rq_async / ndevs;
        rem_async = step + (rq_async % ndevs);
        rem_isoch = rq_isoch - tot_rq;

        /* Distribute the extra RQ slots calculated above and write our
         * isochronous settings out to the actual devices. */
        for (cdev=0; cdev<ndevs; cdev++) {
                cur = master[cdev].dev;
                dev = cur->dev;

                master[cdev].rq += (cdev == ndevs - 1)
                              ? (rem_async + rem_isoch) : step;

                pci_read_config_word(dev, cur->capndx+AGPNICMD, &mnicmd);
                pci_read_config_dword(dev, cur->capndx+AGPCMD, &mcmd);

                mnicmd &= ~(0xff << 8);
                mnicmd &= ~(0x3  << 6);
                mcmd   &= ~(0xff << 24);

                mnicmd |= master[cdev].n  << 8;
                mnicmd |= master[cdev].y  << 6;
                mcmd   |= master[cdev].rq << 24;

                pci_write_config_dword(dev, cur->capndx+AGPCMD, mcmd);
                pci_write_config_word(dev, cur->capndx+AGPNICMD, mnicmd);
        }

free_and_exit:
        kfree(master);

get_out:
        return ret;
}

/*
 * This function basically allocates request queue slots among the
 * AGP 3.0 systems in nonisochronous nodes.  The algorithm is
 * pretty stupid, divide the total number of RQ slots provided by the
 * target by ndevs.  Distribute this many slots to each AGP 3.0 device,
 * giving any left over slots to the last device in dev_list.
 */
static void agp_3_5_nonisochronous_node_enable(struct agp_bridge_data *bridge,
                struct agp_3_5_dev *dev_list, unsigned int ndevs)
{
        struct agp_3_5_dev *cur;
        struct list_head *head = &dev_list->list, *pos;
        u32 tstatus, mcmd;
        u32 trq, mrq, rem;
        unsigned int cdev = 0;

        pci_read_config_dword(bridge->dev, bridge->capndx+AGPSTAT, &tstatus);

        trq = (tstatus >> 24) & 0xff;
        mrq = trq / ndevs;

        rem = mrq + (trq % ndevs);

        for (pos=head->next; cdev<ndevs; cdev++, pos=pos->next) {
                cur = list_entry(pos, struct agp_3_5_dev, list);

                pci_read_config_dword(cur->dev, cur->capndx+AGPCMD, &mcmd);
                mcmd &= ~(0xff << 24);
                mcmd |= ((cdev == ndevs - 1) ? rem : mrq) << 24;
                pci_write_config_dword(cur->dev, cur->capndx+AGPCMD, mcmd);
        }
}

/*
 * Fully configure and enable an AGP 3.0 host bridge and all the devices
 * lying behind it.
 */
int agp_3_5_enable(struct agp_bridge_data *bridge)
{
        struct pci_dev *td = bridge->dev, *dev = NULL;
        u8 mcapndx;
        u32 isoch;
        u32 tstatus, mstatus, ncapid;
        u32 mmajor;
        u16 mpstat;
        struct agp_3_5_dev *dev_list, *cur;
        struct list_head *head, *pos;
        unsigned int ndevs = 0;
        int ret = 0;

        /* Extract some power-on defaults from the target */
        pci_read_config_dword(td, bridge->capndx+AGPSTAT, &tstatus);
        isoch     = (tstatus >> 17) & 0x1;
        if (isoch == 0) /* isoch xfers not available, bail out. */
                return -ENODEV;

        /*
         * Allocate a head for our AGP 3.5 device list
         * (multiple AGP v3 devices are allowed behind a single bridge).
         */
        if ((dev_list = kmalloc(sizeof(*dev_list), GFP_KERNEL)) == NULL) {
                ret = -ENOMEM;
                goto get_out;
        }
        head = &dev_list->list;
        INIT_LIST_HEAD(head);

        /* Find all AGP devices, and add them to dev_list. */
        for_each_pci_dev(dev) {
                mcapndx = pci_find_capability(dev, PCI_CAP_ID_AGP);
                if (mcapndx == 0)
                        continue;

                switch ((dev->class >>8) & 0xff00) {
                        case 0x0600:    /* Bridge */
                                /* Skip bridges. We should call this function for each one. */
                                continue;

                        case 0x0001:    /* Unclassified device */
                                /* Don't know what this is, but log it for investigation. */
                                if (mcapndx != 0) {
                                        dev_info(&td->dev, "wacky, found unclassified AGP device %s [%04x/%04x]\n",
                                                 pci_name(dev),
                                                 dev->vendor, dev->device);
                                }
                                continue;

                        case 0x0300:    /* Display controller */
                        case 0x0400:    /* Multimedia controller */
                                if ((cur = kmalloc(sizeof(*cur), GFP_KERNEL)) == NULL) {
                                        ret = -ENOMEM;
                                        goto free_and_exit;
                                }
                                cur->dev = dev;

                                pos = &cur->list;
                                list_add(pos, head);
                                ndevs++;
                                continue;

                        default:
                                continue;
                }
        }

        /*
         * Take an initial pass through the devices lying behind our host
         * bridge.  Make sure each one is actually an AGP 3.0 device, otherwise
         * exit with an error message.  Along the way store the AGP 3.0
         * cap_ptr for each device
         */
        list_for_each(pos, head) {
                cur = list_entry(pos, struct agp_3_5_dev, list);
                dev = cur->dev;

                pci_read_config_word(dev, PCI_STATUS, &mpstat);
                if ((mpstat & PCI_STATUS_CAP_LIST) == 0)
                        continue;

                pci_read_config_byte(dev, PCI_CAPABILITY_LIST, &mcapndx);
                if (mcapndx != 0) {
                        do {
                                pci_read_config_dword(dev, mcapndx, &ncapid);
                                if ((ncapid & 0xff) != 2)
                                        mcapndx = (ncapid >> 8) & 0xff;
                        }
                        while (((ncapid & 0xff) != 2) && (mcapndx != 0));
                }

                if (mcapndx == 0) {
                        dev_err(&td->dev, "woah!  Non-AGP device %s on "
                                "secondary bus of AGP 3.5 bridge!\n",
                                pci_name(dev));
                        ret = -ENODEV;
                        goto free_and_exit;
                }

                mmajor = (ncapid >> AGP_MAJOR_VERSION_SHIFT) & 0xf;
                if (mmajor < 3) {
                        dev_err(&td->dev, "woah!  AGP 2.0 device %s on "
                                "secondary bus of AGP 3.5 bridge operating "
                                "with AGP 3.0 electricals!\n", pci_name(dev));
                        ret = -ENODEV;
                        goto free_and_exit;
                }

                cur->capndx = mcapndx;

                pci_read_config_dword(dev, cur->capndx+AGPSTAT, &mstatus);

                if (((mstatus >> 3) & 0x1) == 0) {
                        dev_err(&td->dev, "woah!  AGP 3.x device %s not "
                                "operating in AGP 3.x mode on secondary bus "
                                "of AGP 3.5 bridge operating with AGP 3.0 "
                                "electricals!\n", pci_name(dev));
                        ret = -ENODEV;
                        goto free_and_exit;
                }
        }               

        /*
         * Call functions to divide target resources amongst the AGP 3.0
         * masters.  This process is dramatically different depending on
         * whether isochronous transfers are supported.
         */
        if (isoch) {
                ret = agp_3_5_isochronous_node_enable(bridge, dev_list, ndevs);
                if (ret) {
                        dev_info(&td->dev, "something bad happened setting "
                                 "up isochronous xfers; falling back to "
                                 "non-isochronous xfer mode\n");
                } else {
                        goto free_and_exit;
                }
        }
        agp_3_5_nonisochronous_node_enable(bridge, dev_list, ndevs);

free_and_exit:
        /* Be sure to free the dev_list */
        for (pos=head->next; pos!=head; ) {
                cur = list_entry(pos, struct agp_3_5_dev, list);

                pos = pos->next;
                kfree(cur);
        }
        kfree(dev_list);

get_out:
        return ret;
}