/*
 *  Handling of internal CCW device requests.
 *
 *    Copyright IBM Corp. 2009, 2011
 *    Author(s): Peter Oberparleiter <peter.oberparleiter@de.ibm.com>
 */

#define KMSG_COMPONENT "cio"
#define pr_fmt(fmt) KMSG_COMPONENT ": " fmt

#include <linux/types.h>
#include <linux/err.h>
#include <asm/ccwdev.h>
#include <asm/cio.h>

#include "io_sch.h"
#include "cio.h"
#include "device.h"
#include "cio_debug.h"

/**
 * lpm_adjust - adjust path mask
 * @lpm: path mask to adjust
 * @mask: mask of available paths
 *
 * Shift @lpm right until @lpm and @mask have at least one bit in common or
 * until @lpm is zero. Return the resulting lpm.
 */
int lpm_adjust(int lpm, int mask)
{
        while (lpm && ((lpm & mask) == 0))
                lpm >>= 1;
        return lpm;
}

/*
 * Adjust path mask to use next path and reset retry count. Return resulting
 * path mask.
 */
static u16 ccwreq_next_path(struct ccw_device *cdev)
{
        struct ccw_request *req = &cdev->private->req;

        if (!req->singlepath) {
                req->mask = 0;
                goto out;
        }
        req->retries    = req->maxretries;
        req->mask       = lpm_adjust(req->mask >> 1, req->lpm);
out:
        return req->mask;
}

/*
 * Clean up device state and report to callback.
 */
static void ccwreq_stop(struct ccw_device *cdev, int rc)
{
        struct ccw_request *req = &cdev->private->req;

        if (req->done)
                return;
        req->done = 1;
        ccw_device_set_timeout(cdev, 0);
        memset(&cdev->private->irb, 0, sizeof(struct irb));
        if (rc && rc != -ENODEV && req->drc)
                rc = req->drc;
        req->callback(cdev, req->data, rc);
}

/*
 * (Re-)Start the operation until retries and paths are exhausted.
 */
static void ccwreq_do(struct ccw_device *cdev)
{
        struct ccw_request *req = &cdev->private->req;
        struct subchannel *sch = to_subchannel(cdev->dev.parent);
        struct ccw1 *cp = req->cp;
        int rc = -EACCES;

        while (req->mask) {
                if (req->retries-- == 0) {
                        /* Retries exhausted, try next path. */
                        ccwreq_next_path(cdev);
                        continue;
                }
                /* Perform start function. */
                memset(&cdev->private->irb, 0, sizeof(struct irb));
                rc = cio_start(sch, cp, (u8) req->mask);
                if (rc == 0) {
                        /* I/O started successfully. */
                        ccw_device_set_timeout(cdev, req->timeout);
                        return;
                }
                if (rc == -ENODEV) {
                        /* Permanent device error. */
                        break;
                }
                if (rc == -EACCES) {
                        /* Permant path error. */
                        ccwreq_next_path(cdev);
                        continue;
                }
                /* Temporary improper status. */
                rc = cio_clear(sch);
                if (rc)
                        break;
                return;
        }
        ccwreq_stop(cdev, rc);
}

/**
 * ccw_request_start - perform I/O request
 * @cdev: ccw device
 *
 * Perform the I/O request specified by cdev->req.
 */
void ccw_request_start(struct ccw_device *cdev)
{
        struct ccw_request *req = &cdev->private->req;

        if (req->singlepath) {
                /* Try all paths twice to counter link flapping. */
                req->mask = 0x8080;
        } else
                req->mask = req->lpm;

        req->retries    = req->maxretries;
        req->mask       = lpm_adjust(req->mask, req->lpm);
        req->drc        = 0;
        req->done       = 0;
        req->cancel     = 0;
        if (!req->mask)
                goto out_nopath;
        ccwreq_do(cdev);
        return;

out_nopath:
        ccwreq_stop(cdev, -EACCES);
}

/**
 * ccw_request_cancel - cancel running I/O request
 * @cdev: ccw device
 *
 * Cancel the I/O request specified by cdev->req. Return non-zero if request
 * has already finished, zero otherwise.
 */
int ccw_request_cancel(struct ccw_device *cdev)
{
        struct subchannel *sch = to_subchannel(cdev->dev.parent);
        struct ccw_request *req = &cdev->private->req;
        int rc;

        if (req->done)
                return 1;
        req->cancel = 1;
        rc = cio_clear(sch);
        if (rc)
                ccwreq_stop(cdev, rc);
        return 0;
}

/*
 * Return the status of the internal I/O started on the specified ccw device.
 * Perform BASIC SENSE if required.
 */
static enum io_status ccwreq_status(struct ccw_device *cdev, struct irb *lcirb)
{
        struct irb *irb = &cdev->private->irb;
        struct cmd_scsw *scsw = &irb->scsw.cmd;
        enum uc_todo todo;

        /* Perform BASIC SENSE if needed. */
        if (ccw_device_accumulate_and_sense(cdev, lcirb))
                return IO_RUNNING;
        /* Check for halt/clear interrupt. */
        if (scsw->fctl & (SCSW_FCTL_HALT_FUNC | SCSW_FCTL_CLEAR_FUNC))
                return IO_KILLED;
        /* Check for path error. */
        if (scsw->cc == 3 || scsw->pno)
                return IO_PATH_ERROR;
        /* Handle BASIC SENSE data. */
        if (irb->esw.esw0.erw.cons) {
                CIO_TRACE_EVENT(2, "sensedata");
                CIO_HEX_EVENT(2, &cdev->private->dev_id,
                              sizeof(struct ccw_dev_id));
                CIO_HEX_EVENT(2, &cdev->private->irb.ecw, SENSE_MAX_COUNT);
                /* Check for command reject. */
                if (irb->ecw[0] & SNS0_CMD_REJECT)
                        return IO_REJECTED;
                /* Ask the driver what to do */
                if (cdev->drv && cdev->drv->uc_handler) {
                        todo = cdev->drv->uc_handler(cdev, lcirb);
                        CIO_TRACE_EVENT(2, "uc_response");
                        CIO_HEX_EVENT(2, &todo, sizeof(todo));
                        switch (todo) {
                        case UC_TODO_RETRY:
                                return IO_STATUS_ERROR;
                        case UC_TODO_RETRY_ON_NEW_PATH:
                                return IO_PATH_ERROR;
                        case UC_TODO_STOP:
                                return IO_REJECTED;
                        default:
                                return IO_STATUS_ERROR;
                        }
                }
                /* Assume that unexpected SENSE data implies an error. */
                return IO_STATUS_ERROR;
        }
        /* Check for channel errors. */
        if (scsw->cstat != 0)
                return IO_STATUS_ERROR;
        /* Check for device errors. */
        if (scsw->dstat & ~(DEV_STAT_CHN_END | DEV_STAT_DEV_END))
                return IO_STATUS_ERROR;
        /* Check for final state. */
        if (!(scsw->dstat & DEV_STAT_DEV_END))
                return IO_RUNNING;
        /* Check for other improper status. */
        if (scsw->cc == 1 && (scsw->stctl & SCSW_STCTL_ALERT_STATUS))
                return IO_STATUS_ERROR;
        return IO_DONE;
}

/*
 * Log ccw request status.
 */
static void ccwreq_log_status(struct ccw_device *cdev, enum io_status status)
{
        struct ccw_request *req = &cdev->private->req;
        struct {
                struct ccw_dev_id dev_id;
                u16 retries;
                u8 lpm;
                u8 status;
        }  __attribute__ ((packed)) data;
        data.dev_id     = cdev->private->dev_id;
        data.retries    = req->retries;
        data.lpm        = (u8) req->mask;
        data.status     = (u8) status;
        CIO_TRACE_EVENT(2, "reqstat");
        CIO_HEX_EVENT(2, &data, sizeof(data));
}

/**
 * ccw_request_handler - interrupt handler for I/O request procedure.
 * @cdev: ccw device
 *
 * Handle interrupt during I/O request procedure.
 */
void ccw_request_handler(struct ccw_device *cdev)
{
        struct irb *irb = this_cpu_ptr(&cio_irb);
        struct ccw_request *req = &cdev->private->req;
        enum io_status status;
        int rc = -EOPNOTSUPP;

        /* Check status of I/O request. */
        status = ccwreq_status(cdev, irb);
        if (req->filter)
                status = req->filter(cdev, req->data, irb, status);
        if (status != IO_RUNNING)
                ccw_device_set_timeout(cdev, 0);
        if (status != IO_DONE && status != IO_RUNNING)
                ccwreq_log_status(cdev, status);
        switch (status) {
        case IO_DONE:
                break;
        case IO_RUNNING:
                return;
        case IO_REJECTED:
                goto err;
        case IO_PATH_ERROR:
                goto out_next_path;
        case IO_STATUS_ERROR:
                goto out_restart;
        case IO_KILLED:
                /* Check if request was cancelled on purpose. */
                if (req->cancel) {
                        rc = -EIO;
                        goto err;
                }
                goto out_restart;
        }
        /* Check back with request initiator. */
        if (!req->check)
                goto out;
        switch (req->check(cdev, req->data)) {
        case 0:
                break;
        case -EAGAIN:
                goto out_restart;
        case -EACCES:
                goto out_next_path;
        default:
                goto err;
        }
out:
        ccwreq_stop(cdev, 0);
        return;

out_next_path:
        /* Try next path and restart I/O. */
        if (!ccwreq_next_path(cdev)) {
                rc = -EACCES;
                goto err;
        }
out_restart:
        /* Restart. */
        ccwreq_do(cdev);
        return;
err:
        ccwreq_stop(cdev, rc);
}


/**
 * ccw_request_timeout - timeout handler for I/O request procedure
 * @cdev: ccw device
 *
 * Handle timeout during I/O request procedure.
 */
void ccw_request_timeout(struct ccw_device *cdev)
{
        struct subchannel *sch = to_subchannel(cdev->dev.parent);
        struct ccw_request *req = &cdev->private->req;
        int rc = -ENODEV, chp;

        if (cio_update_schib(sch))
                goto err;

        for (chp = 0; chp < 8; chp++) {
                if ((0x80 >> chp) & sch->schib.pmcw.lpum)
                        pr_warn("%s: No interrupt was received within %lus (CS=%02x, DS=%02x, CHPID=%x.%02x)\n",
                                dev_name(&cdev->dev), req->timeout / HZ,
                                scsw_cstat(&sch->schib.scsw),
                                scsw_dstat(&sch->schib.scsw),
                                sch->schid.cssid,
                                sch->schib.pmcw.chpid[chp]);
        }

        if (!ccwreq_next_path(cdev)) {
                /* set the final return code for this request */
                req->drc = -ETIME;
        }
        rc = cio_clear(sch);
        if (rc)
                goto err;
        return;

err:
        ccwreq_stop(cdev, rc);
}

/**
 * ccw_request_notoper - notoper handler for I/O request procedure
 * @cdev: ccw device
 *
 * Handle notoper during I/O request procedure.
 */
void ccw_request_notoper(struct ccw_device *cdev)
{
        ccwreq_stop(cdev, -ENODEV);
}