/*
 *    DIAGNOSE X'2C4' instruction based HMC FTP services, useable on z/VM
 *
 *    Copyright IBM Corp. 2013
 *    Author(s): Ralf Hoppe (rhoppe@de.ibm.com)
 *
 */

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

#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/irq.h>
#include <linux/wait.h>
#include <linux/string.h>
#include <asm/ctl_reg.h>
#include <asm/diag.h>

#include "hmcdrv_ftp.h"
#include "diag_ftp.h"

/* DIAGNOSE X'2C4' return codes in Ry */
#define DIAG_FTP_RET_OK 0 /* HMC FTP started successfully */
#define DIAG_FTP_RET_EBUSY      4 /* HMC FTP service currently busy */
#define DIAG_FTP_RET_EIO        8 /* HMC FTP service I/O error */
/* and an artificial extension */
#define DIAG_FTP_RET_EPERM      2 /* HMC FTP service privilege error */

/* FTP service status codes (after INTR at guest real location 133) */
#define DIAG_FTP_STAT_OK        0U /* request completed successfully */
#define DIAG_FTP_STAT_PGCC      4U /* program check condition */
#define DIAG_FTP_STAT_PGIOE     8U /* paging I/O error */
#define DIAG_FTP_STAT_TIMEOUT   12U /* timeout */
#define DIAG_FTP_STAT_EBASE     16U /* base of error codes from SCLP */
#define DIAG_FTP_STAT_LDFAIL    (DIAG_FTP_STAT_EBASE + 1U) /* failed */
#define DIAG_FTP_STAT_LDNPERM   (DIAG_FTP_STAT_EBASE + 2U) /* not allowed */
#define DIAG_FTP_STAT_LDRUNS    (DIAG_FTP_STAT_EBASE + 3U) /* runs */
#define DIAG_FTP_STAT_LDNRUNS   (DIAG_FTP_STAT_EBASE + 4U) /* not runs */

/**
 * struct diag_ftp_ldfpl - load file FTP parameter list (LDFPL)
 * @bufaddr: real buffer address (at 4k boundary)
 * @buflen: length of buffer
 * @offset: dir/file offset
 * @intparm: interruption parameter (unused)
 * @transferred: bytes transferred
 * @fsize: file size, filled on GET
 * @failaddr: failing address
 * @spare: padding
 * @fident: file name - ASCII
 */
struct diag_ftp_ldfpl {
        u64 bufaddr;
        u64 buflen;
        u64 offset;
        u64 intparm;
        u64 transferred;
        u64 fsize;
        u64 failaddr;
        u64 spare;
        u8 fident[HMCDRV_FTP_FIDENT_MAX];
} __packed;

static DECLARE_COMPLETION(diag_ftp_rx_complete);
static int diag_ftp_subcode;

/**
 * diag_ftp_handler() - FTP services IRQ handler
 * @extirq: external interrupt (sub-) code
 * @param32: 32-bit interruption parameter from &struct diag_ftp_ldfpl
 * @param64: unused (for 64-bit interrupt parameters)
 */
static void diag_ftp_handler(struct ext_code extirq,
                             unsigned int param32,
                             unsigned long param64)
{
        if ((extirq.subcode >> 8) != 8)
                return; /* not a FTP services sub-code */

        inc_irq_stat(IRQEXT_FTP);
        diag_ftp_subcode = extirq.subcode & 0xffU;
        complete(&diag_ftp_rx_complete);
}

/**
 * diag_ftp_2c4() - DIAGNOSE X'2C4' service call
 * @fpl: pointer to prepared LDFPL
 * @cmd: FTP command to be executed
 *
 * Performs a DIAGNOSE X'2C4' call with (input/output) FTP parameter list
 * @fpl and FTP function code @cmd. In case of an error the function does
 * nothing and returns an (negative) error code.
 *
 * Notes:
 * 1. This function only initiates a transfer, so the caller must wait
 *    for completion (asynchronous execution).
 * 2. The FTP parameter list @fpl must be aligned to a double-word boundary.
 * 3. fpl->bufaddr must be a real address, 4k aligned
 */
static int diag_ftp_2c4(struct diag_ftp_ldfpl *fpl,
                        enum hmcdrv_ftp_cmdid cmd)
{
        int rc;

        diag_stat_inc(DIAG_STAT_X2C4);
        asm volatile(
                "       diag    %[addr],%[cmd],0x2c4\n"
                "0:     j       2f\n"
                "1:     la      %[rc],%[err]\n"
                "2:\n"
                EX_TABLE(0b, 1b)
                : [rc] "=d" (rc), "+m" (*fpl)
                : [cmd] "0" (cmd), [addr] "d" (virt_to_phys(fpl)),
                  [err] "i" (DIAG_FTP_RET_EPERM)
                : "cc");

        switch (rc) {
        case DIAG_FTP_RET_OK:
                return 0;
        case DIAG_FTP_RET_EBUSY:
                return -EBUSY;
        case DIAG_FTP_RET_EPERM:
                return -EPERM;
        case DIAG_FTP_RET_EIO:
        default:
                return -EIO;
        }
}

/**
 * diag_ftp_cmd() - executes a DIAG X'2C4' FTP command, targeting a HMC
 * @ftp: pointer to FTP command specification
 * @fsize: return of file size (or NULL if undesirable)
 *
 * Attention: Notice that this function is not reentrant - so the caller
 * must ensure locking.
 *
 * Return: number of bytes read/written or a (negative) error code
 */
ssize_t diag_ftp_cmd(const struct hmcdrv_ftp_cmdspec *ftp, size_t *fsize)
{
        struct diag_ftp_ldfpl *ldfpl;
        ssize_t len;
#ifdef DEBUG
        unsigned long start_jiffies;

        pr_debug("starting DIAG X'2C4' on '%s', requesting %zd bytes\n",
                 ftp->fname, ftp->len);
        start_jiffies = jiffies;
#endif
        init_completion(&diag_ftp_rx_complete);

        ldfpl = (void *) get_zeroed_page(GFP_KERNEL | GFP_DMA);
        if (!ldfpl) {
                len = -ENOMEM;
                goto out;
        }

        len = strlcpy(ldfpl->fident, ftp->fname, sizeof(ldfpl->fident));
        if (len >= HMCDRV_FTP_FIDENT_MAX) {
                len = -EINVAL;
                goto out_free;
        }

        ldfpl->transferred = 0;
        ldfpl->fsize = 0;
        ldfpl->offset = ftp->ofs;
        ldfpl->buflen = ftp->len;
        ldfpl->bufaddr = virt_to_phys(ftp->buf);

        len = diag_ftp_2c4(ldfpl, ftp->id);
        if (len)
                goto out_free;

        /*
         * There is no way to cancel the running diag X'2C4', the code
         * needs to wait unconditionally until the transfer is complete.
         */
        wait_for_completion(&diag_ftp_rx_complete);

#ifdef DEBUG
        pr_debug("completed DIAG X'2C4' after %lu ms\n",
                 (jiffies - start_jiffies) * 1000 / HZ);
        pr_debug("status of DIAG X'2C4' is %u, with %lld/%lld bytes\n",
                 diag_ftp_subcode, ldfpl->transferred, ldfpl->fsize);
#endif

        switch (diag_ftp_subcode) {
        case DIAG_FTP_STAT_OK: /* success */
                len = ldfpl->transferred;
                if (fsize)
                        *fsize = ldfpl->fsize;
                break;
        case DIAG_FTP_STAT_LDNPERM:
                len = -EPERM;
                break;
        case DIAG_FTP_STAT_LDRUNS:
                len = -EBUSY;
                break;
        case DIAG_FTP_STAT_LDFAIL:
                len = -ENOENT; /* no such file or media */
                break;
        default:
                len = -EIO;
                break;
        }

out_free:
        free_page((unsigned long) ldfpl);
out:
        return len;
}

/**
 * diag_ftp_startup() - startup of FTP services, when running on z/VM
 *
 * Return: 0 on success, else an (negative) error code
 */
int diag_ftp_startup(void)
{
        int rc;

        rc = register_external_irq(EXT_IRQ_CP_SERVICE, diag_ftp_handler);
        if (rc)
                return rc;

        irq_subclass_register(IRQ_SUBCLASS_SERVICE_SIGNAL);
        return 0;
}

/**
 * diag_ftp_shutdown() - shutdown of FTP services, when running on z/VM
 */
void diag_ftp_shutdown(void)
{
        irq_subclass_unregister(IRQ_SUBCLASS_SERVICE_SIGNAL);
        unregister_external_irq(EXT_IRQ_CP_SERVICE, diag_ftp_handler);
}