// SPDX-License-Identifier: GPL-2.0
/*
 * Block driver for s390 storage class memory.
 *
 * Copyright IBM Corp. 2012
 * Author(s): Sebastian Ott <sebott@linux.vnet.ibm.com>
 */

#define pr_fmt(fmt) "scm_block: " fmt

#include <linux/interrupt.h>
#include <linux/spinlock.h>
#include <linux/mempool.h>
#include <linux/module.h>
#include <linux/blkdev.h>
#include <linux/blk-mq.h>
#include <linux/slab.h>
#include <linux/list.h>
#include <linux/io.h>
#include <asm/eadm.h>
#include "scm_blk.h"

debug_info_t *scm_debug;
static int scm_major;
static mempool_t *aidaw_pool;
static DEFINE_SPINLOCK(list_lock);
static LIST_HEAD(inactive_requests);
static unsigned int nr_requests = 64;
static unsigned int nr_requests_per_io = 8;
static atomic_t nr_devices = ATOMIC_INIT(0);
module_param(nr_requests, uint, S_IRUGO);
MODULE_PARM_DESC(nr_requests, "Number of parallel requests.");

module_param(nr_requests_per_io, uint, S_IRUGO);
MODULE_PARM_DESC(nr_requests_per_io, "Number of requests per IO.");

MODULE_DESCRIPTION("Block driver for s390 storage class memory.");
MODULE_LICENSE("GPL");
MODULE_ALIAS("scm:scmdev*");

static void __scm_free_rq(struct scm_request *scmrq)
{
        struct aob_rq_header *aobrq = to_aobrq(scmrq);

        free_page((unsigned long) scmrq->aob);
        kfree(scmrq->request);
        kfree(aobrq);
}

static void scm_free_rqs(void)
{
        struct list_head *iter, *safe;
        struct scm_request *scmrq;

        spin_lock_irq(&list_lock);
        list_for_each_safe(iter, safe, &inactive_requests) {
                scmrq = list_entry(iter, struct scm_request, list);
                list_del(&scmrq->list);
                __scm_free_rq(scmrq);
        }
        spin_unlock_irq(&list_lock);

        mempool_destroy(aidaw_pool);
}

static int __scm_alloc_rq(void)
{
        struct aob_rq_header *aobrq;
        struct scm_request *scmrq;

        aobrq = kzalloc(sizeof(*aobrq) + sizeof(*scmrq), GFP_KERNEL);
        if (!aobrq)
                return -ENOMEM;

        scmrq = (void *) aobrq->data;
        scmrq->aob = (void *) get_zeroed_page(GFP_DMA);
        if (!scmrq->aob)
                goto free;

        scmrq->request = kzalloc_objs(scmrq->request[0], nr_requests_per_io);
        if (!scmrq->request)
                goto free;

        INIT_LIST_HEAD(&scmrq->list);
        spin_lock_irq(&list_lock);
        list_add(&scmrq->list, &inactive_requests);
        spin_unlock_irq(&list_lock);

        return 0;
free:
        __scm_free_rq(scmrq);
        return -ENOMEM;
}

static int scm_alloc_rqs(unsigned int nrqs)
{
        int ret = 0;

        aidaw_pool = mempool_create_page_pool(max(nrqs/8, 1U), 0);
        if (!aidaw_pool)
                return -ENOMEM;

        while (nrqs-- && !ret)
                ret = __scm_alloc_rq();

        return ret;
}

static struct scm_request *scm_request_fetch(void)
{
        struct scm_request *scmrq = NULL;

        spin_lock_irq(&list_lock);
        if (list_empty(&inactive_requests))
                goto out;
        scmrq = list_first_entry(&inactive_requests, struct scm_request, list);
        list_del(&scmrq->list);
out:
        spin_unlock_irq(&list_lock);
        return scmrq;
}

static void scm_request_done(struct scm_request *scmrq)
{
        unsigned long flags;
        struct msb *msb;
        u64 aidaw;
        int i;

        for (i = 0; i < nr_requests_per_io && scmrq->request[i]; i++) {
                msb = &scmrq->aob->msb[i];
                aidaw = (u64)dma64_to_virt(msb->data_addr);

                if ((msb->flags & MSB_FLAG_IDA) && aidaw &&
                    IS_ALIGNED(aidaw, PAGE_SIZE))
                        mempool_free(virt_to_page((void *)aidaw), aidaw_pool);
        }

        spin_lock_irqsave(&list_lock, flags);
        list_add(&scmrq->list, &inactive_requests);
        spin_unlock_irqrestore(&list_lock, flags);
}

static bool scm_permit_request(struct scm_blk_dev *bdev, struct request *req)
{
        return rq_data_dir(req) != WRITE || bdev->state != SCM_WR_PROHIBIT;
}

static inline struct aidaw *scm_aidaw_alloc(void)
{
        struct page *page = mempool_alloc(aidaw_pool, GFP_ATOMIC);

        return page ? page_address(page) : NULL;
}

static inline unsigned long scm_aidaw_bytes(struct aidaw *aidaw)
{
        unsigned long _aidaw = (unsigned long) aidaw;
        unsigned long bytes = ALIGN(_aidaw, PAGE_SIZE) - _aidaw;

        return (bytes / sizeof(*aidaw)) * PAGE_SIZE;
}

struct aidaw *scm_aidaw_fetch(struct scm_request *scmrq, unsigned int bytes)
{
        struct aidaw *aidaw;

        if (scm_aidaw_bytes(scmrq->next_aidaw) >= bytes)
                return scmrq->next_aidaw;

        aidaw = scm_aidaw_alloc();
        if (aidaw)
                memset(aidaw, 0, PAGE_SIZE);
        return aidaw;
}

static int scm_request_prepare(struct scm_request *scmrq)
{
        struct scm_blk_dev *bdev = scmrq->bdev;
        struct scm_device *scmdev = bdev->gendisk->private_data;
        int pos = scmrq->aob->request.msb_count;
        struct msb *msb = &scmrq->aob->msb[pos];
        struct request *req = scmrq->request[pos];
        struct req_iterator iter;
        struct aidaw *aidaw;
        struct bio_vec bv;

        aidaw = scm_aidaw_fetch(scmrq, blk_rq_bytes(req));
        if (!aidaw)
                return -ENOMEM;

        msb->bs = MSB_BS_4K;
        scmrq->aob->request.msb_count++;
        msb->scm_addr = scmdev->address + ((u64) blk_rq_pos(req) << 9);
        msb->oc = (rq_data_dir(req) == READ) ? MSB_OC_READ : MSB_OC_WRITE;
        msb->flags |= MSB_FLAG_IDA;
        msb->data_addr = virt_to_dma64(aidaw);

        rq_for_each_segment(bv, req, iter) {
                WARN_ON(bv.bv_offset);
                msb->blk_count += bv.bv_len >> 12;
                aidaw->data_addr = virt_to_dma64(page_address(bv.bv_page));
                aidaw++;
        }

        scmrq->next_aidaw = aidaw;
        return 0;
}

static inline void scm_request_set(struct scm_request *scmrq,
                                   struct request *req)
{
        scmrq->request[scmrq->aob->request.msb_count] = req;
}

static inline void scm_request_init(struct scm_blk_dev *bdev,
                                    struct scm_request *scmrq)
{
        struct aob_rq_header *aobrq = to_aobrq(scmrq);
        struct aob *aob = scmrq->aob;

        memset(scmrq->request, 0,
               nr_requests_per_io * sizeof(scmrq->request[0]));
        memset(aob, 0, sizeof(*aob));
        aobrq->scmdev = bdev->scmdev;
        aob->request.cmd_code = ARQB_CMD_MOVE;
        aob->request.data = (u64) aobrq;
        scmrq->bdev = bdev;
        scmrq->retries = 4;
        scmrq->error = BLK_STS_OK;
        /* We don't use all msbs - place aidaws at the end of the aob page. */
        scmrq->next_aidaw = (void *) &aob->msb[nr_requests_per_io];
}

static void scm_request_requeue(struct scm_request *scmrq)
{
        struct scm_blk_dev *bdev = scmrq->bdev;
        int i;

        for (i = 0; i < nr_requests_per_io && scmrq->request[i]; i++)
                blk_mq_requeue_request(scmrq->request[i], false);

        atomic_dec(&bdev->queued_reqs);
        scm_request_done(scmrq);
        blk_mq_kick_requeue_list(bdev->rq);
}

static void scm_request_finish(struct scm_request *scmrq)
{
        struct scm_blk_dev *bdev = scmrq->bdev;
        blk_status_t *error;
        int i;

        for (i = 0; i < nr_requests_per_io && scmrq->request[i]; i++) {
                error = blk_mq_rq_to_pdu(scmrq->request[i]);
                *error = scmrq->error;
                if (likely(!blk_should_fake_timeout(scmrq->request[i]->q)))
                        blk_mq_complete_request(scmrq->request[i]);
        }

        atomic_dec(&bdev->queued_reqs);
        scm_request_done(scmrq);
}

static void scm_request_start(struct scm_request *scmrq)
{
        struct scm_blk_dev *bdev = scmrq->bdev;

        atomic_inc(&bdev->queued_reqs);
        if (eadm_start_aob(scmrq->aob)) {
                SCM_LOG(5, "no subchannel");
                scm_request_requeue(scmrq);
        }
}

struct scm_queue {
        struct scm_request *scmrq;
        spinlock_t lock;
};

static blk_status_t scm_blk_request(struct blk_mq_hw_ctx *hctx,
                           const struct blk_mq_queue_data *qd)
{
        struct scm_device *scmdev = hctx->queue->queuedata;
        struct scm_blk_dev *bdev = dev_get_drvdata(&scmdev->dev);
        struct scm_queue *sq = hctx->driver_data;
        struct request *req = qd->rq;
        struct scm_request *scmrq;

        spin_lock(&sq->lock);
        if (!scm_permit_request(bdev, req)) {
                spin_unlock(&sq->lock);
                return BLK_STS_RESOURCE;
        }

        scmrq = sq->scmrq;
        if (!scmrq) {
                scmrq = scm_request_fetch();
                if (!scmrq) {
                        SCM_LOG(5, "no request");
                        spin_unlock(&sq->lock);
                        return BLK_STS_RESOURCE;
                }
                scm_request_init(bdev, scmrq);
                sq->scmrq = scmrq;
        }
        scm_request_set(scmrq, req);

        if (scm_request_prepare(scmrq)) {
                SCM_LOG(5, "aidaw alloc failed");
                scm_request_set(scmrq, NULL);

                if (scmrq->aob->request.msb_count)
                        scm_request_start(scmrq);

                sq->scmrq = NULL;
                spin_unlock(&sq->lock);
                return BLK_STS_RESOURCE;
        }
        blk_mq_start_request(req);

        if (qd->last || scmrq->aob->request.msb_count == nr_requests_per_io) {
                scm_request_start(scmrq);
                sq->scmrq = NULL;
        }
        spin_unlock(&sq->lock);
        return BLK_STS_OK;
}

static int scm_blk_init_hctx(struct blk_mq_hw_ctx *hctx, void *data,
                             unsigned int idx)
{
        struct scm_queue *qd = kzalloc_obj(*qd);

        if (!qd)
                return -ENOMEM;

        spin_lock_init(&qd->lock);
        hctx->driver_data = qd;

        return 0;
}

static void scm_blk_exit_hctx(struct blk_mq_hw_ctx *hctx, unsigned int idx)
{
        struct scm_queue *qd = hctx->driver_data;

        WARN_ON(qd->scmrq);
        kfree(hctx->driver_data);
        hctx->driver_data = NULL;
}

static void __scmrq_log_error(struct scm_request *scmrq)
{
        struct aob *aob = scmrq->aob;

        if (scmrq->error == BLK_STS_TIMEOUT)
                SCM_LOG(1, "Request timeout");
        else {
                SCM_LOG(1, "Request error");
                SCM_LOG_HEX(1, &aob->response, sizeof(aob->response));
        }
        if (scmrq->retries)
                SCM_LOG(1, "Retry request");
        else
                pr_err("An I/O operation to SCM failed with rc=%d\n",
                       scmrq->error);
}

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

        if (scmrq->error != BLK_STS_IOERR)
                goto restart;

        /* For -EIO the response block is valid. */
        switch (scmrq->aob->response.eqc) {
        case EQC_WR_PROHIBIT:
                spin_lock_irqsave(&bdev->lock, flags);
                if (bdev->state != SCM_WR_PROHIBIT)
                        pr_info("%lx: Write access to the SCM increment is suspended\n",
                                (unsigned long) bdev->scmdev->address);
                bdev->state = SCM_WR_PROHIBIT;
                spin_unlock_irqrestore(&bdev->lock, flags);
                goto requeue;
        default:
                break;
        }

restart:
        if (!eadm_start_aob(scmrq->aob))
                return;

requeue:
        scm_request_requeue(scmrq);
}

void scm_blk_irq(struct scm_device *scmdev, void *data, blk_status_t error)
{
        struct scm_request *scmrq = data;

        scmrq->error = error;
        if (error) {
                __scmrq_log_error(scmrq);
                if (scmrq->retries-- > 0) {
                        scm_blk_handle_error(scmrq);
                        return;
                }
        }

        scm_request_finish(scmrq);
}

static void scm_blk_request_done(struct request *req)
{
        blk_status_t *error = blk_mq_rq_to_pdu(req);

        blk_mq_end_request(req, *error);
}

static const struct block_device_operations scm_blk_devops = {
        .owner = THIS_MODULE,
};

static const struct blk_mq_ops scm_mq_ops = {
        .queue_rq = scm_blk_request,
        .complete = scm_blk_request_done,
        .init_hctx = scm_blk_init_hctx,
        .exit_hctx = scm_blk_exit_hctx,
};

int scm_blk_dev_setup(struct scm_blk_dev *bdev, struct scm_device *scmdev)
{
        struct queue_limits lim = {
                .logical_block_size     = 1 << 12,
        };
        unsigned int devindex;
        int len, ret;

        lim.max_segments = min(scmdev->nr_max_block,
                (unsigned int) (PAGE_SIZE / sizeof(struct aidaw)));
        lim.max_hw_sectors = lim.max_segments << 3; /* 8 * 512 = blk_size */

        devindex = atomic_inc_return(&nr_devices) - 1;
        /* scma..scmz + scmaa..scmzz */
        if (devindex > 701) {
                ret = -ENODEV;
                goto out;
        }

        bdev->scmdev = scmdev;
        bdev->state = SCM_OPER;
        spin_lock_init(&bdev->lock);
        atomic_set(&bdev->queued_reqs, 0);

        bdev->tag_set.ops = &scm_mq_ops;
        bdev->tag_set.cmd_size = sizeof(blk_status_t);
        bdev->tag_set.nr_hw_queues = nr_requests;
        bdev->tag_set.queue_depth = nr_requests_per_io * nr_requests;
        bdev->tag_set.numa_node = NUMA_NO_NODE;

        ret = blk_mq_alloc_tag_set(&bdev->tag_set);
        if (ret)
                goto out;

        bdev->gendisk = blk_mq_alloc_disk(&bdev->tag_set, &lim, scmdev);
        if (IS_ERR(bdev->gendisk)) {
                ret = PTR_ERR(bdev->gendisk);
                goto out_tag;
        }
        bdev->gendisk->private_data = scmdev;
        bdev->gendisk->fops = &scm_blk_devops;
        bdev->gendisk->major = scm_major;
        bdev->gendisk->first_minor = devindex * SCM_NR_PARTS;
        bdev->gendisk->minors = SCM_NR_PARTS;

        len = snprintf(bdev->gendisk->disk_name, DISK_NAME_LEN, "scm");
        if (devindex > 25) {
                len += snprintf(bdev->gendisk->disk_name + len,
                                DISK_NAME_LEN - len, "%c",
                                'a' + (devindex / 26) - 1);
                devindex = devindex % 26;
        }
        snprintf(bdev->gendisk->disk_name + len, DISK_NAME_LEN - len, "%c",
                 'a' + devindex);

        /* 512 byte sectors */
        set_capacity(bdev->gendisk, scmdev->size >> 9);
        ret = device_add_disk(&scmdev->dev, bdev->gendisk, NULL);
        if (ret)
                goto out_cleanup_disk;

        return 0;

out_cleanup_disk:
        put_disk(bdev->gendisk);
out_tag:
        blk_mq_free_tag_set(&bdev->tag_set);
out:
        atomic_dec(&nr_devices);
        return ret;
}

void scm_blk_dev_cleanup(struct scm_blk_dev *bdev)
{
        del_gendisk(bdev->gendisk);
        put_disk(bdev->gendisk);
        blk_mq_free_tag_set(&bdev->tag_set);
}

void scm_blk_set_available(struct scm_blk_dev *bdev)
{
        unsigned long flags;

        spin_lock_irqsave(&bdev->lock, flags);
        if (bdev->state == SCM_WR_PROHIBIT)
                pr_info("%lx: Write access to the SCM increment is restored\n",
                        (unsigned long) bdev->scmdev->address);
        bdev->state = SCM_OPER;
        spin_unlock_irqrestore(&bdev->lock, flags);
}

static bool __init scm_blk_params_valid(void)
{
        if (!nr_requests_per_io || nr_requests_per_io > 64)
                return false;

        return true;
}

static int __init scm_blk_init(void)
{
        int ret = -EINVAL;

        if (!scm_blk_params_valid())
                goto out;

        ret = register_blkdev(0, "scm");
        if (ret < 0)
                goto out;

        scm_major = ret;
        ret = scm_alloc_rqs(nr_requests);
        if (ret)
                goto out_free;

        scm_debug = debug_register("scm_log", 16, 1, 16);
        if (!scm_debug) {
                ret = -ENOMEM;
                goto out_free;
        }

        debug_register_view(scm_debug, &debug_hex_ascii_view);
        debug_set_level(scm_debug, 2);

        ret = scm_drv_init();
        if (ret)
                goto out_dbf;

        return ret;

out_dbf:
        debug_unregister(scm_debug);
out_free:
        scm_free_rqs();
        unregister_blkdev(scm_major, "scm");
out:
        return ret;
}
module_init(scm_blk_init);

static void __exit scm_blk_cleanup(void)
{
        scm_drv_cleanup();
        debug_unregister(scm_debug);
        scm_free_rqs();
        unregister_blkdev(scm_major, "scm");
}
module_exit(scm_blk_cleanup);