/*
 * Block driver for s390 storage class memory.
 *
 * Copyright IBM Corp. 2012
 * Author(s): Sebastian Ott <sebott@linux.vnet.ibm.com>
 */

#include <linux/spinlock.h>
#include <linux/module.h>
#include <linux/blkdev.h>
#include <linux/genhd.h>
#include <linux/slab.h>
#include <linux/list.h>
#include <asm/eadm.h>
#include "scm_blk.h"

static unsigned int write_cluster_size = 64;
module_param(write_cluster_size, uint, S_IRUGO);
MODULE_PARM_DESC(write_cluster_size,
                 "Number of pages used for contiguous writes.");

#define CLUSTER_SIZE (write_cluster_size * PAGE_SIZE)

void __scm_free_rq_cluster(struct scm_request *scmrq)
{
        int i;

        if (!scmrq->cluster.buf)
                return;

        for (i = 0; i < 2 * write_cluster_size; i++)
                free_page((unsigned long) scmrq->cluster.buf[i]);

        kfree(scmrq->cluster.buf);
}

int __scm_alloc_rq_cluster(struct scm_request *scmrq)
{
        int i;

        scmrq->cluster.buf = kzalloc(sizeof(void *) * 2 * write_cluster_size,
                                 GFP_KERNEL);
        if (!scmrq->cluster.buf)
                return -ENOMEM;

        for (i = 0; i < 2 * write_cluster_size; i++) {
                scmrq->cluster.buf[i] = (void *) get_zeroed_page(GFP_DMA);
                if (!scmrq->cluster.buf[i])
                        return -ENOMEM;
        }
        INIT_LIST_HEAD(&scmrq->cluster.list);
        return 0;
}

void scm_request_cluster_init(struct scm_request *scmrq)
{
        scmrq->cluster.state = CLUSTER_NONE;
}

static bool clusters_intersect(struct request *A, struct request *B)
{
        unsigned long firstA, lastA, firstB, lastB;

        firstA = ((u64) blk_rq_pos(A) << 9) / CLUSTER_SIZE;
        lastA = (((u64) blk_rq_pos(A) << 9) +
                    blk_rq_bytes(A) - 1) / CLUSTER_SIZE;

        firstB = ((u64) blk_rq_pos(B) << 9) / CLUSTER_SIZE;
        lastB = (((u64) blk_rq_pos(B) << 9) +
                    blk_rq_bytes(B) - 1) / CLUSTER_SIZE;

        return (firstB <= lastA && firstA <= lastB);
}

bool scm_reserve_cluster(struct scm_request *scmrq)
{
        struct request *req = scmrq->request[scmrq->aob->request.msb_count];
        struct scm_blk_dev *bdev = scmrq->bdev;
        struct scm_request *iter;
        int pos, add = 1;

        if (write_cluster_size == 0)
                return true;

        spin_lock(&bdev->lock);
        list_for_each_entry(iter, &bdev->cluster_list, cluster.list) {
                if (iter == scmrq) {
                        /*
                         * We don't have to use clusters_intersect here, since
                         * cluster requests are always started separately.
                         */
                        add = 0;
                        continue;
                }
                for (pos = 0; pos < iter->aob->request.msb_count; pos++) {
                        if (clusters_intersect(req, iter->request[pos]) &&
                            (rq_data_dir(req) == WRITE ||
                             rq_data_dir(iter->request[pos]) == WRITE)) {
                                spin_unlock(&bdev->lock);
                                return false;
                        }
                }
        }
        if (add)
                list_add(&scmrq->cluster.list, &bdev->cluster_list);
        spin_unlock(&bdev->lock);

        return true;
}

void scm_release_cluster(struct scm_request *scmrq)
{
        struct scm_blk_dev *bdev = scmrq->bdev;
        unsigned long flags;

        if (write_cluster_size == 0)
                return;

        spin_lock_irqsave(&bdev->lock, flags);
        list_del(&scmrq->cluster.list);
        spin_unlock_irqrestore(&bdev->lock, flags);
}

void scm_blk_dev_cluster_setup(struct scm_blk_dev *bdev)
{
        INIT_LIST_HEAD(&bdev->cluster_list);
        blk_queue_io_opt(bdev->rq, CLUSTER_SIZE);
}

static int scm_prepare_cluster_request(struct scm_request *scmrq)
{
        struct scm_blk_dev *bdev = scmrq->bdev;
        struct scm_device *scmdev = bdev->gendisk->private_data;
        struct request *req = scmrq->request[0];
        struct msb *msb = &scmrq->aob->msb[0];
        struct req_iterator iter;
        struct aidaw *aidaw;
        struct bio_vec bv;
        int i = 0;
        u64 addr;

        switch (scmrq->cluster.state) {
        case CLUSTER_NONE:
                scmrq->cluster.state = CLUSTER_READ;
                /* fall through */
        case CLUSTER_READ:
                msb->bs = MSB_BS_4K;
                msb->oc = MSB_OC_READ;
                msb->flags = MSB_FLAG_IDA;
                msb->blk_count = write_cluster_size;

                addr = scmdev->address + ((u64) blk_rq_pos(req) << 9);
                msb->scm_addr = round_down(addr, CLUSTER_SIZE);

                if (msb->scm_addr !=
                    round_down(addr + (u64) blk_rq_bytes(req) - 1,
                               CLUSTER_SIZE))
                        msb->blk_count = 2 * write_cluster_size;

                aidaw = scm_aidaw_fetch(scmrq, msb->blk_count * PAGE_SIZE);
                if (!aidaw)
                        return -ENOMEM;

                scmrq->aob->request.msb_count = 1;
                msb->data_addr = (u64) aidaw;
                for (i = 0; i < msb->blk_count; i++) {
                        aidaw->data_addr = (u64) scmrq->cluster.buf[i];
                        aidaw++;
                }

                break;
        case CLUSTER_WRITE:
                aidaw = (void *) msb->data_addr;
                msb->oc = MSB_OC_WRITE;

                for (addr = msb->scm_addr;
                     addr < scmdev->address + ((u64) blk_rq_pos(req) << 9);
                     addr += PAGE_SIZE) {
                        aidaw->data_addr = (u64) scmrq->cluster.buf[i];
                        aidaw++;
                        i++;
                }
                rq_for_each_segment(bv, req, iter) {
                        aidaw->data_addr = (u64) page_address(bv.bv_page);
                        aidaw++;
                        i++;
                }
                for (; i < msb->blk_count; i++) {
                        aidaw->data_addr = (u64) scmrq->cluster.buf[i];
                        aidaw++;
                }
                break;
        }
        return 0;
}

bool scm_need_cluster_request(struct scm_request *scmrq)
{
        int pos = scmrq->aob->request.msb_count;

        if (rq_data_dir(scmrq->request[pos]) == READ)
                return false;

        return blk_rq_bytes(scmrq->request[pos]) < CLUSTER_SIZE;
}

/* Called with queue lock held. */
void scm_initiate_cluster_request(struct scm_request *scmrq)
{
        if (scm_prepare_cluster_request(scmrq))
                goto requeue;
        if (eadm_start_aob(scmrq->aob))
                goto requeue;
        return;
requeue:
        scm_request_requeue(scmrq);
}

bool scm_test_cluster_request(struct scm_request *scmrq)
{
        return scmrq->cluster.state != CLUSTER_NONE;
}

void scm_cluster_request_irq(struct scm_request *scmrq)
{
        struct scm_blk_dev *bdev = scmrq->bdev;
        unsigned long flags;

        switch (scmrq->cluster.state) {
        case CLUSTER_NONE:
                BUG();
                break;
        case CLUSTER_READ:
                if (scmrq->error) {
                        scm_request_finish(scmrq);
                        break;
                }
                scmrq->cluster.state = CLUSTER_WRITE;
                spin_lock_irqsave(&bdev->rq_lock, flags);
                scm_initiate_cluster_request(scmrq);
                spin_unlock_irqrestore(&bdev->rq_lock, flags);
                break;
        case CLUSTER_WRITE:
                scm_request_finish(scmrq);
                break;
        }
}

bool scm_cluster_size_valid(void)
{
        if (write_cluster_size == 1 || write_cluster_size > 128)
                return false;

        return !(write_cluster_size & (write_cluster_size - 1));
}