// SPDX-License-Identifier: GPL-2.0
/*
 *  Functions for incremental construction of fcx enabled I/O control blocks.
 *
 *    Copyright IBM Corp. 2008
 *    Author(s): Peter Oberparleiter <peter.oberparleiter@de.ibm.com>
 */

#include <linux/kernel.h>
#include <linux/types.h>
#include <linux/string.h>
#include <linux/errno.h>
#include <linux/err.h>
#include <linux/module.h>
#include <asm/fcx.h>
#include <asm/itcw.h>

/*
 * struct itcw - incremental tcw helper data type
 *
 * This structure serves as a handle for the incremental construction of a
 * tcw and associated tccb, tsb, data tidaw-list plus an optional interrogate
 * tcw and associated data. The data structures are contained inside a single
 * contiguous buffer provided by the user.
 *
 * The itcw construction functions take care of overall data integrity:
 * - reset unused fields to zero
 * - fill in required pointers
 * - ensure required alignment for data structures
 * - prevent data structures to cross 4k-byte boundary where required
 * - calculate tccb-related length fields
 * - optionally provide ready-made interrogate tcw and associated structures
 *
 * Restrictions apply to the itcws created with these construction functions:
 * - tida only supported for data address, not for tccb
 * - only contiguous tidaw-lists (no ttic)
 * - total number of bytes required per itcw may not exceed 4k bytes
 * - either read or write operation (may not work with r=0 and w=0)
 *
 * Example:
 * struct itcw *itcw;
 * void *buffer;
 * size_t size;
 *
 * size = itcw_calc_size(1, 2, 0);
 * buffer = kmalloc(size, GFP_KERNEL | GFP_DMA);
 * if (!buffer)
 *      return -ENOMEM;
 * itcw = itcw_init(buffer, size, ITCW_OP_READ, 1, 2, 0);
 * if (IS_ERR(itcw))
 *      return PTR_ER(itcw);
 * itcw_add_dcw(itcw, 0x2, 0, NULL, 0, 72);
 * itcw_add_tidaw(itcw, 0, 0x30000, 20);
 * itcw_add_tidaw(itcw, 0, 0x40000, 52);
 * itcw_finalize(itcw);
 *
 */
struct itcw {
        struct tcw *tcw;
        struct tcw *intrg_tcw;
        int num_tidaws;
        int max_tidaws;
        int intrg_num_tidaws;
        int intrg_max_tidaws;
};

/**
 * itcw_get_tcw - return pointer to tcw associated with the itcw
 * @itcw: address of the itcw
 *
 * Return pointer to the tcw associated with the itcw.
 */
struct tcw *itcw_get_tcw(struct itcw *itcw)
{
        return itcw->tcw;
}
EXPORT_SYMBOL(itcw_get_tcw);

/**
 * itcw_calc_size - return the size of an itcw with the given parameters
 * @intrg: if non-zero, add an interrogate tcw
 * @max_tidaws: maximum number of tidaws to be used for data addressing or zero
 * if no tida is to be used.
 * @intrg_max_tidaws: maximum number of tidaws to be used for data addressing
 * by the interrogate tcw, if specified
 *
 * Calculate and return the number of bytes required to hold an itcw with the
 * given parameters and assuming tccbs with maximum size.
 *
 * Note that the resulting size also contains bytes needed for alignment
 * padding as well as padding to ensure that data structures don't cross a
 * 4k-boundary where required.
 */
size_t itcw_calc_size(int intrg, int max_tidaws, int intrg_max_tidaws)
{
        size_t len;
        int cross_count;

        /* Main data. */
        len = sizeof(struct itcw);
        len += /* TCW */ sizeof(struct tcw) + /* TCCB */ TCCB_MAX_SIZE +
               /* TSB */ sizeof(struct tsb) +
               /* TIDAL */ max_tidaws * sizeof(struct tidaw);
        /* Interrogate data. */
        if (intrg) {
                len += /* TCW */ sizeof(struct tcw) + /* TCCB */ TCCB_MAX_SIZE +
                       /* TSB */ sizeof(struct tsb) +
                       /* TIDAL */ intrg_max_tidaws * sizeof(struct tidaw);
        }

        /* Maximum required alignment padding. */
        len += /* Initial TCW */ 63 + /* Interrogate TCCB */ 7;

        /* TIDAW lists may not cross a 4k boundary. To cross a
         * boundary we need to add a TTIC TIDAW. We need to reserve
         * one additional TIDAW for a TTIC that we may need to add due
         * to the placement of the data chunk in memory, and a further
         * TIDAW for each page boundary that the TIDAW list may cross
         * due to it's own size.
         */
        if (max_tidaws) {
                cross_count = 1 + ((max_tidaws * sizeof(struct tidaw) - 1)
                                   >> PAGE_SHIFT);
                len += cross_count * sizeof(struct tidaw);
        }
        if (intrg_max_tidaws) {
                cross_count = 1 + ((intrg_max_tidaws * sizeof(struct tidaw) - 1)
                                   >> PAGE_SHIFT);
                len += cross_count * sizeof(struct tidaw);
        }
        return len;
}
EXPORT_SYMBOL(itcw_calc_size);

#define CROSS4K(x, l)   (((x) & ~4095) != ((x + l) & ~4095))

static inline void *fit_chunk(addr_t *start, addr_t end, size_t len,
                              int align, int check_4k)
{
        addr_t addr;

        addr = ALIGN(*start, align);
        if (check_4k && CROSS4K(addr, len)) {
                addr = ALIGN(addr, 4096);
                addr = ALIGN(addr, align);
        }
        if (addr + len > end)
                return ERR_PTR(-ENOSPC);
        *start = addr + len;
        return (void *) addr;
}

/**
 * itcw_init - initialize incremental tcw data structure
 * @buffer: address of buffer to use for data structures
 * @size: number of bytes in buffer
 * @op: %ITCW_OP_READ for a read operation tcw, %ITCW_OP_WRITE for a write
 * operation tcw
 * @intrg: if non-zero, add and initialize an interrogate tcw
 * @max_tidaws: maximum number of tidaws to be used for data addressing or zero
 * if no tida is to be used.
 * @intrg_max_tidaws: maximum number of tidaws to be used for data addressing
 * by the interrogate tcw, if specified
 *
 * Prepare the specified buffer to be used as an incremental tcw, i.e. a
 * helper data structure that can be used to construct a valid tcw by
 * successive calls to other helper functions. Note: the buffer needs to be
 * located below the 2G address limit. The resulting tcw has the following
 * restrictions:
 *  - no tccb tidal
 *  - input/output tidal is contiguous (no ttic)
 *  - total data should not exceed 4k
 *  - tcw specifies either read or write operation
 *
 * On success, return pointer to the resulting incremental tcw data structure,
 * ERR_PTR otherwise.
 */
struct itcw *itcw_init(void *buffer, size_t size, int op, int intrg,
                       int max_tidaws, int intrg_max_tidaws)
{
        struct itcw *itcw;
        void *chunk;
        addr_t start;
        addr_t end;
        int cross_count;

        /* Check for 2G limit. */
        start = (addr_t) buffer;
        end = start + size;
        if (end > (1 << 31))
                return ERR_PTR(-EINVAL);
        memset(buffer, 0, size);
        /* ITCW. */
        chunk = fit_chunk(&start, end, sizeof(struct itcw), 1, 0);
        if (IS_ERR(chunk))
                return chunk;
        itcw = chunk;
        /* allow for TTIC tidaws that may be needed to cross a page boundary */
        cross_count = 0;
        if (max_tidaws)
                cross_count = 1 + ((max_tidaws * sizeof(struct tidaw) - 1)
                                   >> PAGE_SHIFT);
        itcw->max_tidaws = max_tidaws + cross_count;
        cross_count = 0;
        if (intrg_max_tidaws)
                cross_count = 1 + ((intrg_max_tidaws * sizeof(struct tidaw) - 1)
                                   >> PAGE_SHIFT);
        itcw->intrg_max_tidaws = intrg_max_tidaws + cross_count;
        /* Main TCW. */
        chunk = fit_chunk(&start, end, sizeof(struct tcw), 64, 0);
        if (IS_ERR(chunk))
                return chunk;
        itcw->tcw = chunk;
        tcw_init(itcw->tcw, (op == ITCW_OP_READ) ? 1 : 0,
                 (op == ITCW_OP_WRITE) ? 1 : 0);
        /* Interrogate TCW. */
        if (intrg) {
                chunk = fit_chunk(&start, end, sizeof(struct tcw), 64, 0);
                if (IS_ERR(chunk))
                        return chunk;
                itcw->intrg_tcw = chunk;
                tcw_init(itcw->intrg_tcw, 1, 0);
                tcw_set_intrg(itcw->tcw, itcw->intrg_tcw);
        }
        /* Data TIDAL. */
        if (max_tidaws > 0) {
                chunk = fit_chunk(&start, end, sizeof(struct tidaw) *
                                  itcw->max_tidaws, 16, 0);
                if (IS_ERR(chunk))
                        return chunk;
                tcw_set_data(itcw->tcw, chunk, 1);
        }
        /* Interrogate data TIDAL. */
        if (intrg && (intrg_max_tidaws > 0)) {
                chunk = fit_chunk(&start, end, sizeof(struct tidaw) *
                                  itcw->intrg_max_tidaws, 16, 0);
                if (IS_ERR(chunk))
                        return chunk;
                tcw_set_data(itcw->intrg_tcw, chunk, 1);
        }
        /* TSB. */
        chunk = fit_chunk(&start, end, sizeof(struct tsb), 8, 0);
        if (IS_ERR(chunk))
                return chunk;
        tsb_init(chunk);
        tcw_set_tsb(itcw->tcw, chunk);
        /* Interrogate TSB. */
        if (intrg) {
                chunk = fit_chunk(&start, end, sizeof(struct tsb), 8, 0);
                if (IS_ERR(chunk))
                        return chunk;
                tsb_init(chunk);
                tcw_set_tsb(itcw->intrg_tcw, chunk);
        }
        /* TCCB. */
        chunk = fit_chunk(&start, end, TCCB_MAX_SIZE, 8, 0);
        if (IS_ERR(chunk))
                return chunk;
        tccb_init(chunk, TCCB_MAX_SIZE, TCCB_SAC_DEFAULT);
        tcw_set_tccb(itcw->tcw, chunk);
        /* Interrogate TCCB. */
        if (intrg) {
                chunk = fit_chunk(&start, end, TCCB_MAX_SIZE, 8, 0);
                if (IS_ERR(chunk))
                        return chunk;
                tccb_init(chunk, TCCB_MAX_SIZE, TCCB_SAC_INTRG);
                tcw_set_tccb(itcw->intrg_tcw, chunk);
                tccb_add_dcw(chunk, TCCB_MAX_SIZE, DCW_CMD_INTRG, 0, NULL,
                             sizeof(struct dcw_intrg_data), 0);
                tcw_finalize(itcw->intrg_tcw, 0);
        }
        return itcw;
}
EXPORT_SYMBOL(itcw_init);

/**
 * itcw_add_dcw - add a dcw to the itcw
 * @itcw: address of the itcw
 * @cmd: the dcw command
 * @flags: flags for the dcw
 * @cd: address of control data for this dcw or NULL if none is required
 * @cd_count: number of control data bytes for this dcw
 * @count: number of data bytes for this dcw
 *
 * Add a new dcw to the specified itcw by writing the dcw information specified
 * by @cmd, @flags, @cd, @cd_count and @count to the tca of the tccb. Return
 * a pointer to the newly added dcw on success or -%ENOSPC if the new dcw
 * would exceed the available space.
 *
 * Note: the tcal field of the tccb header will be updated to reflect added
 * content.
 */
struct dcw *itcw_add_dcw(struct itcw *itcw, u8 cmd, u8 flags, void *cd,
                         u8 cd_count, u32 count)
{
        return tccb_add_dcw(tcw_get_tccb(itcw->tcw), TCCB_MAX_SIZE, cmd,
                            flags, cd, cd_count, count);
}
EXPORT_SYMBOL(itcw_add_dcw);

/**
 * itcw_add_tidaw - add a tidaw to the itcw
 * @itcw: address of the itcw
 * @flags: flags for the new tidaw
 * @addr: address value for the new tidaw
 * @count: count value for the new tidaw
 *
 * Add a new tidaw to the input/output data tidaw-list of the specified itcw
 * (depending on the value of the r-flag and w-flag). Return a pointer to
 * the new tidaw on success or -%ENOSPC if the new tidaw would exceed the
 * available space.
 *
 * Note: TTIC tidaws are automatically added when needed, so explicitly calling
 * this interface with the TTIC flag is not supported. The last-tidaw flag
 * for the last tidaw in the list will be set by itcw_finalize.
 */
struct tidaw *itcw_add_tidaw(struct itcw *itcw, u8 flags, void *addr, u32 count)
{
        struct tidaw *following;

        if (itcw->num_tidaws >= itcw->max_tidaws)
                return ERR_PTR(-ENOSPC);
        /*
         * Is the tidaw, which follows the one we are about to fill, on the next
         * page? Then we have to insert a TTIC tidaw first, that points to the
         * tidaw on the new page.
         */
        following = ((struct tidaw *) tcw_get_data(itcw->tcw))
                + itcw->num_tidaws + 1;
        if (itcw->num_tidaws && !((unsigned long) following & ~PAGE_MASK)) {
                tcw_add_tidaw(itcw->tcw, itcw->num_tidaws++,
                              TIDAW_FLAGS_TTIC, following, 0);
                if (itcw->num_tidaws >= itcw->max_tidaws)
                        return ERR_PTR(-ENOSPC);
        }
        return tcw_add_tidaw(itcw->tcw, itcw->num_tidaws++, flags, addr, count);
}
EXPORT_SYMBOL(itcw_add_tidaw);

/**
 * itcw_set_data - set data address and tida flag of the itcw
 * @itcw: address of the itcw
 * @addr: the data address
 * @use_tidal: zero of the data address specifies a contiguous block of data,
 * non-zero if it specifies a list if tidaws.
 *
 * Set the input/output data address of the itcw (depending on the value of the
 * r-flag and w-flag). If @use_tidal is non-zero, the corresponding tida flag
 * is set as well.
 */
void itcw_set_data(struct itcw *itcw, void *addr, int use_tidal)
{
        tcw_set_data(itcw->tcw, addr, use_tidal);
}
EXPORT_SYMBOL(itcw_set_data);

/**
 * itcw_finalize - calculate length and count fields of the itcw
 * @itcw: address of the itcw
 *
 * Calculate tcw input-/output-count and tccbl fields and add a tcat the tccb.
 * In case input- or output-tida is used, the tidaw-list must be stored in
 * continuous storage (no ttic). The tcal field in the tccb must be
 * up-to-date.
 */
void itcw_finalize(struct itcw *itcw)
{
        tcw_finalize(itcw->tcw, itcw->num_tidaws);
}
EXPORT_SYMBOL(itcw_finalize);