/*
 *  Driver for the NXP SAA7164 PCIe bridge
 *
 *  Copyright (c) 2010-2015 Steven Toth <stoth@kernellabs.com>
 *
 *  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.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *
 *  GNU General Public License for more details.
 */

#include "saa7164.h"

/* The message bus to/from the firmware is a ring buffer in PCI address
 * space. Establish the defaults.
 */
int saa7164_bus_setup(struct saa7164_dev *dev)
{
        struct tmComResBusInfo *b       = &dev->bus;

        mutex_init(&b->lock);

        b->Type                 = TYPE_BUS_PCIe;
        b->m_wMaxReqSize        = SAA_DEVICE_MAXREQUESTSIZE;

        b->m_pdwSetRing         = (u8 __iomem *)(dev->bmmio +
                ((u32)dev->busdesc.CommandRing));

        b->m_dwSizeSetRing      = SAA_DEVICE_BUFFERBLOCKSIZE;

        b->m_pdwGetRing         = (u8 __iomem *)(dev->bmmio +
                ((u32)dev->busdesc.ResponseRing));

        b->m_dwSizeGetRing      = SAA_DEVICE_BUFFERBLOCKSIZE;

        b->m_dwSetWritePos      = ((u32)dev->intfdesc.BARLocation) +
                (2 * sizeof(u64));
        b->m_dwSetReadPos       = b->m_dwSetWritePos + (1 * sizeof(u32));

        b->m_dwGetWritePos      = b->m_dwSetWritePos + (2 * sizeof(u32));
        b->m_dwGetReadPos       = b->m_dwSetWritePos + (3 * sizeof(u32));

        return 0;
}

void saa7164_bus_dump(struct saa7164_dev *dev)
{
        struct tmComResBusInfo *b = &dev->bus;

        dprintk(DBGLVL_BUS, "Dumping the bus structure:\n");
        dprintk(DBGLVL_BUS, " .type             = %d\n", b->Type);
        dprintk(DBGLVL_BUS, " .dev->bmmio       = 0x%p\n", dev->bmmio);
        dprintk(DBGLVL_BUS, " .m_wMaxReqSize    = 0x%x\n", b->m_wMaxReqSize);
        dprintk(DBGLVL_BUS, " .m_pdwSetRing     = 0x%p\n", b->m_pdwSetRing);
        dprintk(DBGLVL_BUS, " .m_dwSizeSetRing  = 0x%x\n", b->m_dwSizeSetRing);
        dprintk(DBGLVL_BUS, " .m_pdwGetRing     = 0x%p\n", b->m_pdwGetRing);
        dprintk(DBGLVL_BUS, " .m_dwSizeGetRing  = 0x%x\n", b->m_dwSizeGetRing);

        dprintk(DBGLVL_BUS, " .m_dwSetReadPos   = 0x%x (0x%08x)\n",
                b->m_dwSetReadPos, saa7164_readl(b->m_dwSetReadPos));

        dprintk(DBGLVL_BUS, " .m_dwSetWritePos  = 0x%x (0x%08x)\n",
                b->m_dwSetWritePos, saa7164_readl(b->m_dwSetWritePos));

        dprintk(DBGLVL_BUS, " .m_dwGetReadPos   = 0x%x (0x%08x)\n",
                b->m_dwGetReadPos, saa7164_readl(b->m_dwGetReadPos));

        dprintk(DBGLVL_BUS, " .m_dwGetWritePos  = 0x%x (0x%08x)\n",
                b->m_dwGetWritePos, saa7164_readl(b->m_dwGetWritePos));

}

/* Intensionally throw a BUG() if the state of the message bus looks corrupt */
static void saa7164_bus_verify(struct saa7164_dev *dev)
{
        struct tmComResBusInfo *b = &dev->bus;
        int bug = 0;

        if (saa7164_readl(b->m_dwSetReadPos) > b->m_dwSizeSetRing)
                bug++;

        if (saa7164_readl(b->m_dwSetWritePos) > b->m_dwSizeSetRing)
                bug++;

        if (saa7164_readl(b->m_dwGetReadPos) > b->m_dwSizeGetRing)
                bug++;

        if (saa7164_readl(b->m_dwGetWritePos) > b->m_dwSizeGetRing)
                bug++;

        if (bug) {
                saa_debug = 0xffff; /* Ensure we get the bus dump */
                saa7164_bus_dump(dev);
                saa_debug = 1024; /* Ensure we get the bus dump */
                BUG();
        }
}

static void saa7164_bus_dumpmsg(struct saa7164_dev *dev, struct tmComResInfo *m,
                                void *buf)
{
        dprintk(DBGLVL_BUS, "Dumping msg structure:\n");
        dprintk(DBGLVL_BUS, " .id               = %d\n",   m->id);
        dprintk(DBGLVL_BUS, " .flags            = 0x%x\n", m->flags);
        dprintk(DBGLVL_BUS, " .size             = 0x%x\n", m->size);
        dprintk(DBGLVL_BUS, " .command          = 0x%x\n", m->command);
        dprintk(DBGLVL_BUS, " .controlselector  = 0x%x\n", m->controlselector);
        dprintk(DBGLVL_BUS, " .seqno            = %d\n",   m->seqno);
        if (buf)
                dprintk(DBGLVL_BUS, " .buffer (ignored)\n");
}

/*
 * Places a command or a response on the bus. The implementation does not
 * know if it is a command or a response it just places the data on the
 * bus depending on the bus information given in the struct tmComResBusInfo
 * structure. If the command or response does not fit into the bus ring
 * buffer it will be refused.
 *
 * Return Value:
 *  SAA_OK     The function executed successfully.
 *  < 0        One or more members are not initialized.
 */
int saa7164_bus_set(struct saa7164_dev *dev, struct tmComResInfo* msg,
        void *buf)
{
        struct tmComResBusInfo *bus = &dev->bus;
        u32 bytes_to_write, free_write_space, timeout, curr_srp, curr_swp;
        u32 new_swp, space_rem;
        int ret = SAA_ERR_BAD_PARAMETER;
        u16 size;

        if (!msg) {
                printk(KERN_ERR "%s() !msg\n", __func__);
                return SAA_ERR_BAD_PARAMETER;
        }

        dprintk(DBGLVL_BUS, "%s()\n", __func__);

        saa7164_bus_verify(dev);

        if (msg->size > dev->bus.m_wMaxReqSize) {
                printk(KERN_ERR "%s() Exceeded dev->bus.m_wMaxReqSize\n",
                        __func__);
                return SAA_ERR_BAD_PARAMETER;
        }

        if ((msg->size > 0) && (buf == NULL)) {
                printk(KERN_ERR "%s() Missing message buffer\n", __func__);
                return SAA_ERR_BAD_PARAMETER;
        }

        /* Lock the bus from any other access */
        mutex_lock(&bus->lock);

        bytes_to_write = sizeof(*msg) + msg->size;
        free_write_space = 0;
        timeout = SAA_BUS_TIMEOUT;
        curr_srp = saa7164_readl(bus->m_dwSetReadPos);
        curr_swp = saa7164_readl(bus->m_dwSetWritePos);

        /* Deal with ring wrapping issues */
        if (curr_srp > curr_swp)
                /* Deal with the wrapped ring */
                free_write_space = curr_srp - curr_swp;
        else
                /* The ring has not wrapped yet */
                free_write_space = (curr_srp + bus->m_dwSizeSetRing) - curr_swp;

        dprintk(DBGLVL_BUS, "%s() bytes_to_write = %d\n", __func__,
                bytes_to_write);

        dprintk(DBGLVL_BUS, "%s() free_write_space = %d\n", __func__,
                free_write_space);

        dprintk(DBGLVL_BUS, "%s() curr_srp = %x\n", __func__, curr_srp);
        dprintk(DBGLVL_BUS, "%s() curr_swp = %x\n", __func__, curr_swp);

        /* Process the msg and write the content onto the bus */
        while (bytes_to_write >= free_write_space) {

                if (timeout-- == 0) {
                        printk(KERN_ERR "%s() bus timeout\n", __func__);
                        ret = SAA_ERR_NO_RESOURCES;
                        goto out;
                }

                /* TODO: Review this delay, efficient? */
                /* Wait, allowing the hardware fetch time */
                mdelay(1);

                /* Check the space usage again */
                curr_srp = saa7164_readl(bus->m_dwSetReadPos);

                /* Deal with ring wrapping issues */
                if (curr_srp > curr_swp)
                        /* Deal with the wrapped ring */
                        free_write_space = curr_srp - curr_swp;
                else
                        /* Read didn't wrap around the buffer */
                        free_write_space = (curr_srp + bus->m_dwSizeSetRing) -
                                curr_swp;

        }

        /* Calculate the new write position */
        new_swp = curr_swp + bytes_to_write;

        dprintk(DBGLVL_BUS, "%s() new_swp = %x\n", __func__, new_swp);
        dprintk(DBGLVL_BUS, "%s() bus->m_dwSizeSetRing = %x\n", __func__,
                bus->m_dwSizeSetRing);

        /*
         * Make a copy of msg->size before it is converted to le16 since it is
         * used in the code below.
         */
        size = msg->size;
        /* Convert to le16/le32 */
        msg->size = (__force u16)cpu_to_le16(msg->size);
        msg->command = (__force u32)cpu_to_le32(msg->command);
        msg->controlselector = (__force u16)cpu_to_le16(msg->controlselector);

        /* Mental Note: line 462 tmmhComResBusPCIe.cpp */

        /* Check if we're going to wrap again */
        if (new_swp > bus->m_dwSizeSetRing) {

                /* Ring wraps */
                new_swp -= bus->m_dwSizeSetRing;

                space_rem = bus->m_dwSizeSetRing - curr_swp;

                dprintk(DBGLVL_BUS, "%s() space_rem = %x\n", __func__,
                        space_rem);

                dprintk(DBGLVL_BUS, "%s() sizeof(*msg) = %d\n", __func__,
                        (u32)sizeof(*msg));

                if (space_rem < sizeof(*msg)) {
                        dprintk(DBGLVL_BUS, "%s() tr4\n", __func__);

                        /* Split the msg into pieces as the ring wraps */
                        memcpy_toio(bus->m_pdwSetRing + curr_swp, msg, space_rem);
                        memcpy_toio(bus->m_pdwSetRing, (u8 *)msg + space_rem,
                                sizeof(*msg) - space_rem);

                        memcpy_toio(bus->m_pdwSetRing + sizeof(*msg) - space_rem,
                                buf, size);

                } else if (space_rem == sizeof(*msg)) {
                        dprintk(DBGLVL_BUS, "%s() tr5\n", __func__);

                        /* Additional data at the beginning of the ring */
                        memcpy_toio(bus->m_pdwSetRing + curr_swp, msg, sizeof(*msg));
                        memcpy_toio(bus->m_pdwSetRing, buf, size);

                } else {
                        /* Additional data wraps around the ring */
                        memcpy_toio(bus->m_pdwSetRing + curr_swp, msg, sizeof(*msg));
                        if (size > 0) {
                                memcpy_toio(bus->m_pdwSetRing + curr_swp +
                                        sizeof(*msg), buf, space_rem -
                                        sizeof(*msg));
                                memcpy_toio(bus->m_pdwSetRing, (u8 *)buf +
                                        space_rem - sizeof(*msg),
                                        bytes_to_write - space_rem);
                        }

                }

        } /* (new_swp > bus->m_dwSizeSetRing) */
        else {
                dprintk(DBGLVL_BUS, "%s() tr6\n", __func__);

                /* The ring buffer doesn't wrap, two simple copies */
                memcpy_toio(bus->m_pdwSetRing + curr_swp, msg, sizeof(*msg));
                memcpy_toio(bus->m_pdwSetRing + curr_swp + sizeof(*msg), buf,
                        size);
        }

        dprintk(DBGLVL_BUS, "%s() new_swp = %x\n", __func__, new_swp);

        /* Update the bus write position */
        saa7164_writel(bus->m_dwSetWritePos, new_swp);

        /* Convert back to cpu after writing the msg to the ringbuffer. */
        msg->size = le16_to_cpu((__force __le16)msg->size);
        msg->command = le32_to_cpu((__force __le32)msg->command);
        msg->controlselector = le16_to_cpu((__force __le16)msg->controlselector);
        ret = SAA_OK;

out:
        saa7164_bus_dump(dev);
        mutex_unlock(&bus->lock);
        saa7164_bus_verify(dev);
        return ret;
}

/*
 * Receive a command or a response from the bus. The implementation does not
 * know if it is a command or a response it simply dequeues the data,
 * depending on the bus information given in the struct tmComResBusInfo
 * structure.
 *
 * Return Value:
 *  0          The function executed successfully.
 *  < 0        One or more members are not initialized.
 */
int saa7164_bus_get(struct saa7164_dev *dev, struct tmComResInfo* msg,
        void *buf, int peekonly)
{
        struct tmComResBusInfo *bus = &dev->bus;
        u32 bytes_to_read, write_distance, curr_grp, curr_gwp,
                new_grp, buf_size, space_rem;
        struct tmComResInfo msg_tmp;
        int ret = SAA_ERR_BAD_PARAMETER;

        saa7164_bus_verify(dev);

        if (msg == NULL)
                return ret;

        if (msg->size > dev->bus.m_wMaxReqSize) {
                printk(KERN_ERR "%s() Exceeded dev->bus.m_wMaxReqSize\n",
                        __func__);
                return ret;
        }

        if ((peekonly == 0) && (msg->size > 0) && (buf == NULL)) {
                printk(KERN_ERR
                        "%s() Missing msg buf, size should be %d bytes\n",
                        __func__, msg->size);
                return ret;
        }

        mutex_lock(&bus->lock);

        /* Peek the bus to see if a msg exists, if it's not what we're expecting
         * then return cleanly else read the message from the bus.
         */
        curr_gwp = saa7164_readl(bus->m_dwGetWritePos);
        curr_grp = saa7164_readl(bus->m_dwGetReadPos);

        if (curr_gwp == curr_grp) {
                ret = SAA_ERR_EMPTY;
                goto out;
        }

        bytes_to_read = sizeof(*msg);

        /* Calculate write distance to current read position */
        write_distance = 0;
        if (curr_gwp >= curr_grp)
                /* Write doesn't wrap around the ring */
                write_distance = curr_gwp - curr_grp;
        else
                /* Write wraps around the ring */
                write_distance = curr_gwp + bus->m_dwSizeGetRing - curr_grp;

        if (bytes_to_read > write_distance) {
                printk(KERN_ERR "%s() No message/response found\n", __func__);
                ret = SAA_ERR_INVALID_COMMAND;
                goto out;
        }

        /* Calculate the new read position */
        new_grp = curr_grp + bytes_to_read;
        if (new_grp > bus->m_dwSizeGetRing) {

                /* Ring wraps */
                new_grp -= bus->m_dwSizeGetRing;
                space_rem = bus->m_dwSizeGetRing - curr_grp;

                memcpy_fromio(&msg_tmp, bus->m_pdwGetRing + curr_grp, space_rem);
                memcpy_fromio((u8 *)&msg_tmp + space_rem, bus->m_pdwGetRing,
                        bytes_to_read - space_rem);

        } else {
                /* No wrapping */
                memcpy_fromio(&msg_tmp, bus->m_pdwGetRing + curr_grp, bytes_to_read);
        }
        /* Convert from little endian to CPU */
        msg_tmp.size = le16_to_cpu((__force __le16)msg_tmp.size);
        msg_tmp.command = le32_to_cpu((__force __le32)msg_tmp.command);
        msg_tmp.controlselector = le16_to_cpu((__force __le16)msg_tmp.controlselector);
        memcpy(msg, &msg_tmp, sizeof(*msg));

        /* No need to update the read positions, because this was a peek */
        /* If the caller specifically want to peek, return */
        if (peekonly) {
                goto peekout;
        }

        /* Check if the command/response matches what is expected */
        if ((msg_tmp.id != msg->id) || (msg_tmp.command != msg->command) ||
                (msg_tmp.controlselector != msg->controlselector) ||
                (msg_tmp.seqno != msg->seqno) || (msg_tmp.size != msg->size)) {

                printk(KERN_ERR "%s() Unexpected msg miss-match\n", __func__);
                saa7164_bus_dumpmsg(dev, msg, buf);
                saa7164_bus_dumpmsg(dev, &msg_tmp, NULL);
                ret = SAA_ERR_INVALID_COMMAND;
                goto out;
        }

        /* Get the actual command and response from the bus */
        buf_size = msg->size;

        bytes_to_read = sizeof(*msg) + msg->size;
        /* Calculate write distance to current read position */
        write_distance = 0;
        if (curr_gwp >= curr_grp)
                /* Write doesn't wrap around the ring */
                write_distance = curr_gwp - curr_grp;
        else
                /* Write wraps around the ring */
                write_distance = curr_gwp + bus->m_dwSizeGetRing - curr_grp;

        if (bytes_to_read > write_distance) {
                printk(KERN_ERR "%s() Invalid bus state, missing msg or mangled ring, faulty H/W / bad code?\n",
                       __func__);
                ret = SAA_ERR_INVALID_COMMAND;
                goto out;
        }

        /* Calculate the new read position */
        new_grp = curr_grp + bytes_to_read;
        if (new_grp > bus->m_dwSizeGetRing) {

                /* Ring wraps */
                new_grp -= bus->m_dwSizeGetRing;
                space_rem = bus->m_dwSizeGetRing - curr_grp;

                if (space_rem < sizeof(*msg)) {
                        if (buf)
                                memcpy_fromio(buf, bus->m_pdwGetRing + sizeof(*msg) -
                                        space_rem, buf_size);

                } else if (space_rem == sizeof(*msg)) {
                        if (buf)
                                memcpy_fromio(buf, bus->m_pdwGetRing, buf_size);
                } else {
                        /* Additional data wraps around the ring */
                        if (buf) {
                                memcpy_fromio(buf, bus->m_pdwGetRing + curr_grp +
                                        sizeof(*msg), space_rem - sizeof(*msg));
                                memcpy_fromio(buf + space_rem - sizeof(*msg),
                                        bus->m_pdwGetRing, bytes_to_read -
                                        space_rem);
                        }

                }

        } else {
                /* No wrapping */
                if (buf)
                        memcpy_fromio(buf, bus->m_pdwGetRing + curr_grp + sizeof(*msg),
                                buf_size);
        }

        /* Update the read positions, adjusting the ring */
        saa7164_writel(bus->m_dwGetReadPos, new_grp);

peekout:
        ret = SAA_OK;
out:
        mutex_unlock(&bus->lock);
        saa7164_bus_verify(dev);
        return ret;
}