/*
 * PowerNV LPC bus handling.
 *
 * Copyright 2013 IBM Corp.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version
 * 2 of the License, or (at your option) any later version.
 */

#include <linux/kernel.h>
#include <linux/of.h>
#include <linux/bug.h>
#include <linux/debugfs.h>
#include <linux/io.h>
#include <linux/slab.h>

#include <asm/machdep.h>
#include <asm/firmware.h>
#include <asm/xics.h>
#include <asm/opal.h>
#include <asm/prom.h>
#include <asm/uaccess.h>
#include <asm/debug.h>

static int opal_lpc_chip_id = -1;

static u8 opal_lpc_inb(unsigned long port)
{
        int64_t rc;
        __be32 data;

        if (opal_lpc_chip_id < 0 || port > 0xffff)
                return 0xff;
        rc = opal_lpc_read(opal_lpc_chip_id, OPAL_LPC_IO, port, &data, 1);
        return rc ? 0xff : be32_to_cpu(data);
}

static __le16 __opal_lpc_inw(unsigned long port)
{
        int64_t rc;
        __be32 data;

        if (opal_lpc_chip_id < 0 || port > 0xfffe)
                return 0xffff;
        if (port & 1)
                return (__le16)opal_lpc_inb(port) << 8 | opal_lpc_inb(port + 1);
        rc = opal_lpc_read(opal_lpc_chip_id, OPAL_LPC_IO, port, &data, 2);
        return rc ? 0xffff : be32_to_cpu(data);
}
static u16 opal_lpc_inw(unsigned long port)
{
        return le16_to_cpu(__opal_lpc_inw(port));
}

static __le32 __opal_lpc_inl(unsigned long port)
{
        int64_t rc;
        __be32 data;

        if (opal_lpc_chip_id < 0 || port > 0xfffc)
                return 0xffffffff;
        if (port & 3)
                return (__le32)opal_lpc_inb(port    ) << 24 |
                       (__le32)opal_lpc_inb(port + 1) << 16 |
                       (__le32)opal_lpc_inb(port + 2) <<  8 |
                               opal_lpc_inb(port + 3);
        rc = opal_lpc_read(opal_lpc_chip_id, OPAL_LPC_IO, port, &data, 4);
        return rc ? 0xffffffff : be32_to_cpu(data);
}

static u32 opal_lpc_inl(unsigned long port)
{
        return le32_to_cpu(__opal_lpc_inl(port));
}

static void opal_lpc_outb(u8 val, unsigned long port)
{
        if (opal_lpc_chip_id < 0 || port > 0xffff)
                return;
        opal_lpc_write(opal_lpc_chip_id, OPAL_LPC_IO, port, val, 1);
}

static void __opal_lpc_outw(__le16 val, unsigned long port)
{
        if (opal_lpc_chip_id < 0 || port > 0xfffe)
                return;
        if (port & 1) {
                opal_lpc_outb(val >> 8, port);
                opal_lpc_outb(val     , port + 1);
                return;
        }
        opal_lpc_write(opal_lpc_chip_id, OPAL_LPC_IO, port, val, 2);
}

static void opal_lpc_outw(u16 val, unsigned long port)
{
        __opal_lpc_outw(cpu_to_le16(val), port);
}

static void __opal_lpc_outl(__le32 val, unsigned long port)
{
        if (opal_lpc_chip_id < 0 || port > 0xfffc)
                return;
        if (port & 3) {
                opal_lpc_outb(val >> 24, port);
                opal_lpc_outb(val >> 16, port + 1);
                opal_lpc_outb(val >>  8, port + 2);
                opal_lpc_outb(val      , port + 3);
                return;
        }
        opal_lpc_write(opal_lpc_chip_id, OPAL_LPC_IO, port, val, 4);
}

static void opal_lpc_outl(u32 val, unsigned long port)
{
        __opal_lpc_outl(cpu_to_le32(val), port);
}

static void opal_lpc_insb(unsigned long p, void *b, unsigned long c)
{
        u8 *ptr = b;

        while(c--)
                *(ptr++) = opal_lpc_inb(p);
}

static void opal_lpc_insw(unsigned long p, void *b, unsigned long c)
{
        __le16 *ptr = b;

        while(c--)
                *(ptr++) = __opal_lpc_inw(p);
}

static void opal_lpc_insl(unsigned long p, void *b, unsigned long c)
{
        __le32 *ptr = b;

        while(c--)
                *(ptr++) = __opal_lpc_inl(p);
}

static void opal_lpc_outsb(unsigned long p, const void *b, unsigned long c)
{
        const u8 *ptr = b;

        while(c--)
                opal_lpc_outb(*(ptr++), p);
}

static void opal_lpc_outsw(unsigned long p, const void *b, unsigned long c)
{
        const __le16 *ptr = b;

        while(c--)
                __opal_lpc_outw(*(ptr++), p);
}

static void opal_lpc_outsl(unsigned long p, const void *b, unsigned long c)
{
        const __le32 *ptr = b;

        while(c--)
                __opal_lpc_outl(*(ptr++), p);
}

static const struct ppc_pci_io opal_lpc_io = {
        .inb    = opal_lpc_inb,
        .inw    = opal_lpc_inw,
        .inl    = opal_lpc_inl,
        .outb   = opal_lpc_outb,
        .outw   = opal_lpc_outw,
        .outl   = opal_lpc_outl,
        .insb   = opal_lpc_insb,
        .insw   = opal_lpc_insw,
        .insl   = opal_lpc_insl,
        .outsb  = opal_lpc_outsb,
        .outsw  = opal_lpc_outsw,
        .outsl  = opal_lpc_outsl,
};

#ifdef CONFIG_DEBUG_FS
struct lpc_debugfs_entry {
        enum OpalLPCAddressType lpc_type;
};

static ssize_t lpc_debug_read(struct file *filp, char __user *ubuf,
                              size_t count, loff_t *ppos)
{
        struct lpc_debugfs_entry *lpc = filp->private_data;
        u32 data, pos, len, todo;
        int rc;

        if (!access_ok(VERIFY_WRITE, ubuf, count))
                return -EFAULT;

        todo = count;
        while (todo) {
                pos = *ppos;

                /*
                 * Select access size based on count and alignment and
                 * access type. IO and MEM only support byte acceses,
                 * FW supports all 3.
                 */
                len = 1;
                if (lpc->lpc_type == OPAL_LPC_FW) {
                        if (todo > 3 && (pos & 3) == 0)
                                len = 4;
                        else if (todo > 1 && (pos & 1) == 0)
                                len = 2;
                }
                rc = opal_lpc_read(opal_lpc_chip_id, lpc->lpc_type, pos,
                                   &data, len);
                if (rc)
                        return -ENXIO;

                /*
                 * Now there is some trickery with the data returned by OPAL
                 * as it's the desired data right justified in a 32-bit BE
                 * word.
                 *
                 * This is a very bad interface and I'm to blame for it :-(
                 *
                 * So we can't just apply a 32-bit swap to what comes from OPAL,
                 * because user space expects the *bytes* to be in their proper
                 * respective positions (ie, LPC position).
                 *
                 * So what we really want to do here is to shift data right
                 * appropriately on a LE kernel.
                 *
                 * IE. If the LPC transaction has bytes B0, B1, B2 and B3 in that
                 * order, we have in memory written to by OPAL at the "data"
                 * pointer:
                 *
                 *               Bytes:      OPAL "data"   LE "data"
                 *   32-bit:   B0 B1 B2 B3   B0B1B2B3      B3B2B1B0
                 *   16-bit:   B0 B1         0000B0B1      B1B00000
                 *    8-bit:   B0            000000B0      B0000000
                 *
                 * So a BE kernel will have the leftmost of the above in the MSB
                 * and rightmost in the LSB and can just then "cast" the u32 "data"
                 * down to the appropriate quantity and write it.
                 *
                 * However, an LE kernel can't. It doesn't need to swap because a
                 * load from data followed by a store to user are going to preserve
                 * the byte ordering which is the wire byte order which is what the
                 * user wants, but in order to "crop" to the right size, we need to
                 * shift right first.
                 */
                switch(len) {
                case 4:
                        rc = __put_user((u32)data, (u32 __user *)ubuf);
                        break;
                case 2:
#ifdef __LITTLE_ENDIAN__
                        data >>= 16;
#endif
                        rc = __put_user((u16)data, (u16 __user *)ubuf);
                        break;
                default:
#ifdef __LITTLE_ENDIAN__
                        data >>= 24;
#endif
                        rc = __put_user((u8)data, (u8 __user *)ubuf);
                        break;
                }
                if (rc)
                        return -EFAULT;
                *ppos += len;
                ubuf += len;
                todo -= len;
        }

        return count;
}

static ssize_t lpc_debug_write(struct file *filp, const char __user *ubuf,
                               size_t count, loff_t *ppos)
{
        struct lpc_debugfs_entry *lpc = filp->private_data;
        u32 data, pos, len, todo;
        int rc;

        if (!access_ok(VERIFY_READ, ubuf, count))
                return -EFAULT;

        todo = count;
        while (todo) {
                pos = *ppos;

                /*
                 * Select access size based on count and alignment and
                 * access type. IO and MEM only support byte acceses,
                 * FW supports all 3.
                 */
                len = 1;
                if (lpc->lpc_type == OPAL_LPC_FW) {
                        if (todo > 3 && (pos & 3) == 0)
                                len = 4;
                        else if (todo > 1 && (pos & 1) == 0)
                                len = 2;
                }

                /*
                 * Similarly to the read case, we have some trickery here but
                 * it's different to handle. We need to pass the value to OPAL in
                 * a register whose layout depends on the access size. We want
                 * to reproduce the memory layout of the user, however we aren't
                 * doing a load from user and a store to another memory location
                 * which would achieve that. Here we pass the value to OPAL via
                 * a register which is expected to contain the "BE" interpretation
                 * of the byte sequence. IE: for a 32-bit access, byte 0 should be
                 * in the MSB. So here we *do* need to byteswap on LE.
                 *
                 *           User bytes:    LE "data"  OPAL "data"
                 *  32-bit:  B0 B1 B2 B3    B3B2B1B0   B0B1B2B3
                 *  16-bit:  B0 B1          0000B1B0   0000B0B1
                 *   8-bit:  B0             000000B0   000000B0
                 */
                switch(len) {
                case 4:
                        rc = __get_user(data, (u32 __user *)ubuf);
                        data = cpu_to_be32(data);
                        break;
                case 2:
                        rc = __get_user(data, (u16 __user *)ubuf);
                        data = cpu_to_be16(data);
                        break;
                default:
                        rc = __get_user(data, (u8 __user *)ubuf);
                        break;
                }
                if (rc)
                        return -EFAULT;

                rc = opal_lpc_write(opal_lpc_chip_id, lpc->lpc_type, pos,
                                    data, len);
                if (rc)
                        return -ENXIO;
                *ppos += len;
                ubuf += len;
                todo -= len;
        }

        return count;
}

static const struct file_operations lpc_fops = {
        .read =         lpc_debug_read,
        .write =        lpc_debug_write,
        .open =         simple_open,
        .llseek =       default_llseek,
};

static int opal_lpc_debugfs_create_type(struct dentry *folder,
                                        const char *fname,
                                        enum OpalLPCAddressType type)
{
        struct lpc_debugfs_entry *entry;
        entry = kzalloc(sizeof(*entry), GFP_KERNEL);
        if (!entry)
                return -ENOMEM;
        entry->lpc_type = type;
        debugfs_create_file(fname, 0600, folder, entry, &lpc_fops);
        return 0;
}

static int opal_lpc_init_debugfs(void)
{
        struct dentry *root;
        int rc = 0;

        if (opal_lpc_chip_id < 0)
                return -ENODEV;

        root = debugfs_create_dir("lpc", powerpc_debugfs_root);

        rc |= opal_lpc_debugfs_create_type(root, "io", OPAL_LPC_IO);
        rc |= opal_lpc_debugfs_create_type(root, "mem", OPAL_LPC_MEM);
        rc |= opal_lpc_debugfs_create_type(root, "fw", OPAL_LPC_FW);
        return rc;
}
machine_device_initcall(powernv, opal_lpc_init_debugfs);
#endif  /* CONFIG_DEBUG_FS */

void opal_lpc_init(void)
{
        struct device_node *np;

        /*
         * Look for a Power8 LPC bus tagged as "primary",
         * we currently support only one though the OPAL APIs
         * support any number.
         */
        for_each_compatible_node(np, NULL, "ibm,power8-lpc") {
                if (!of_device_is_available(np))
                        continue;
                if (!of_get_property(np, "primary", NULL))
                        continue;
                opal_lpc_chip_id = of_get_ibm_chip_id(np);
                break;
        }
        if (opal_lpc_chip_id < 0)
                return;

        /* Setup special IO ops */
        ppc_pci_io = opal_lpc_io;
        isa_io_special = true;

        pr_info("OPAL: Power8 LPC bus found, chip ID %d\n", opal_lpc_chip_id);
}