// SPDX-License-Identifier: GPL-2.0-only
/*
 * LocalPlus Bus FIFO driver for the Freescale MPC52xx.
 *
 * Copyright (C) 2009 Secret Lab Technologies Ltd.
 *
 * Todo:
 * - Add support for multiple requests to be queued.
 */

#include <linux/interrupt.h>
#include <linux/kernel.h>
#include <linux/of.h>
#include <linux/of_platform.h>
#include <linux/spinlock.h>
#include <linux/module.h>
#include <asm/io.h>
#include <asm/prom.h>
#include <asm/mpc52xx.h>
#include <asm/time.h>

#include <linux/fsl/bestcomm/bestcomm.h>
#include <linux/fsl/bestcomm/bestcomm_priv.h>
#include <linux/fsl/bestcomm/gen_bd.h>

MODULE_AUTHOR("Grant Likely <grant.likely@secretlab.ca>");
MODULE_DESCRIPTION("MPC5200 LocalPlus FIFO device driver");
MODULE_LICENSE("GPL");

#define LPBFIFO_REG_PACKET_SIZE         (0x00)
#define LPBFIFO_REG_START_ADDRESS       (0x04)
#define LPBFIFO_REG_CONTROL             (0x08)
#define LPBFIFO_REG_ENABLE              (0x0C)
#define LPBFIFO_REG_BYTES_DONE_STATUS   (0x14)
#define LPBFIFO_REG_FIFO_DATA           (0x40)
#define LPBFIFO_REG_FIFO_STATUS         (0x44)
#define LPBFIFO_REG_FIFO_CONTROL        (0x48)
#define LPBFIFO_REG_FIFO_ALARM          (0x4C)

struct mpc52xx_lpbfifo {
        struct device *dev;
        phys_addr_t regs_phys;
        void __iomem *regs;
        int irq;
        spinlock_t lock;

        struct bcom_task *bcom_tx_task;
        struct bcom_task *bcom_rx_task;
        struct bcom_task *bcom_cur_task;

        /* Current state data */
        struct mpc52xx_lpbfifo_request *req;
        int dma_irqs_enabled;
};

/* The MPC5200 has only one fifo, so only need one instance structure */
static struct mpc52xx_lpbfifo lpbfifo;

/**
 * mpc52xx_lpbfifo_kick - Trigger the next block of data to be transferred
 */
static void mpc52xx_lpbfifo_kick(struct mpc52xx_lpbfifo_request *req)
{
        size_t transfer_size = req->size - req->pos;
        struct bcom_bd *bd;
        void __iomem *reg;
        u32 *data;
        int i;
        int bit_fields;
        int dma = !(req->flags & MPC52XX_LPBFIFO_FLAG_NO_DMA);
        int write = req->flags & MPC52XX_LPBFIFO_FLAG_WRITE;
        int poll_dma = req->flags & MPC52XX_LPBFIFO_FLAG_POLL_DMA;

        /* Set and clear the reset bits; is good practice in User Manual */
        out_be32(lpbfifo.regs + LPBFIFO_REG_ENABLE, 0x01010000);

        /* set master enable bit */
        out_be32(lpbfifo.regs + LPBFIFO_REG_ENABLE, 0x00000001);
        if (!dma) {
                /* While the FIFO can be setup for transfer sizes as large as
                 * 16M-1, the FIFO itself is only 512 bytes deep and it does
                 * not generate interrupts for FIFO full events (only transfer
                 * complete will raise an IRQ).  Therefore when not using
                 * Bestcomm to drive the FIFO it needs to either be polled, or
                 * transfers need to constrained to the size of the fifo.
                 *
                 * This driver restricts the size of the transfer
                 */
                if (transfer_size > 512)
                        transfer_size = 512;

                /* Load the FIFO with data */
                if (write) {
                        reg = lpbfifo.regs + LPBFIFO_REG_FIFO_DATA;
                        data = req->data + req->pos;
                        for (i = 0; i < transfer_size; i += 4)
                                out_be32(reg, *data++);
                }

                /* Unmask both error and completion irqs */
                out_be32(lpbfifo.regs + LPBFIFO_REG_ENABLE, 0x00000301);
        } else {
                /* Choose the correct direction
                 *
                 * Configure the watermarks so DMA will always complete correctly.
                 * It may be worth experimenting with the ALARM value to see if
                 * there is a performance impacit.  However, if it is wrong there
                 * is a risk of DMA not transferring the last chunk of data
                 */
                if (write) {
                        out_be32(lpbfifo.regs + LPBFIFO_REG_FIFO_ALARM, 0x1e4);
                        out_8(lpbfifo.regs + LPBFIFO_REG_FIFO_CONTROL, 7);
                        lpbfifo.bcom_cur_task = lpbfifo.bcom_tx_task;
                } else {
                        out_be32(lpbfifo.regs + LPBFIFO_REG_FIFO_ALARM, 0x1ff);
                        out_8(lpbfifo.regs + LPBFIFO_REG_FIFO_CONTROL, 0);
                        lpbfifo.bcom_cur_task = lpbfifo.bcom_rx_task;

                        if (poll_dma) {
                                if (lpbfifo.dma_irqs_enabled) {
                                        disable_irq(bcom_get_task_irq(lpbfifo.bcom_rx_task));
                                        lpbfifo.dma_irqs_enabled = 0;
                                }
                        } else {
                                if (!lpbfifo.dma_irqs_enabled) {
                                        enable_irq(bcom_get_task_irq(lpbfifo.bcom_rx_task));
                                        lpbfifo.dma_irqs_enabled = 1;
                                }
                        }
                }

                bd = bcom_prepare_next_buffer(lpbfifo.bcom_cur_task);
                bd->status = transfer_size;
                if (!write) {
                        /*
                         * In the DMA read case, the DMA doesn't complete,
                         * possibly due to incorrect watermarks in the ALARM
                         * and CONTROL regs. For now instead of trying to
                         * determine the right watermarks that will make this
                         * work, just increase the number of bytes the FIFO is
                         * expecting.
                         *
                         * When submitting another operation, the FIFO will get
                         * reset, so the condition of the FIFO waiting for a
                         * non-existent 4 bytes will get cleared.
                         */
                        transfer_size += 4; /* BLECH! */
                }
                bd->data[0] = req->data_phys + req->pos;
                bcom_submit_next_buffer(lpbfifo.bcom_cur_task, NULL);

                /* error irq & master enabled bit */
                bit_fields = 0x00000201;

                /* Unmask irqs */
                if (write && (!poll_dma))
                        bit_fields |= 0x00000100; /* completion irq too */
                out_be32(lpbfifo.regs + LPBFIFO_REG_ENABLE, bit_fields);
        }

        /* Set transfer size, width, chip select and READ mode */
        out_be32(lpbfifo.regs + LPBFIFO_REG_START_ADDRESS,
                 req->offset + req->pos);
        out_be32(lpbfifo.regs + LPBFIFO_REG_PACKET_SIZE, transfer_size);

        bit_fields = req->cs << 24 | 0x000008;
        if (!write)
                bit_fields |= 0x010000; /* read mode */
        out_be32(lpbfifo.regs + LPBFIFO_REG_CONTROL, bit_fields);

        /* Kick it off */
        if (!lpbfifo.req->defer_xfer_start)
                out_8(lpbfifo.regs + LPBFIFO_REG_PACKET_SIZE, 0x01);
        if (dma)
                bcom_enable(lpbfifo.bcom_cur_task);
}

/**
 * mpc52xx_lpbfifo_irq - IRQ handler for LPB FIFO
 *
 * On transmit, the dma completion irq triggers before the fifo completion
 * triggers.  Handle the dma completion here instead of the LPB FIFO Bestcomm
 * task completion irq because everything is not really done until the LPB FIFO
 * completion irq triggers.
 *
 * In other words:
 * For DMA, on receive, the "Fat Lady" is the bestcom completion irq. on
 * transmit, the fifo completion irq is the "Fat Lady". The opera (or in this
 * case the DMA/FIFO operation) is not finished until the "Fat Lady" sings.
 *
 * Reasons for entering this routine:
 * 1) PIO mode rx and tx completion irq
 * 2) DMA interrupt mode tx completion irq
 * 3) DMA polled mode tx
 *
 * Exit conditions:
 * 1) Transfer aborted
 * 2) FIFO complete without DMA; more data to do
 * 3) FIFO complete without DMA; all data transferred
 * 4) FIFO complete using DMA
 *
 * Condition 1 can occur regardless of whether or not DMA is used.
 * It requires executing the callback to report the error and exiting
 * immediately.
 *
 * Condition 2 requires programming the FIFO with the next block of data
 *
 * Condition 3 requires executing the callback to report completion
 *
 * Condition 4 means the same as 3, except that we also retrieve the bcom
 * buffer so DMA doesn't get clogged up.
 *
 * To make things trickier, the spinlock must be dropped before
 * executing the callback, otherwise we could end up with a deadlock
 * or nested spinlock condition.  The out path is non-trivial, so
 * extra fiddling is done to make sure all paths lead to the same
 * outbound code.
 */
static irqreturn_t mpc52xx_lpbfifo_irq(int irq, void *dev_id)
{
        struct mpc52xx_lpbfifo_request *req;
        u32 status = in_8(lpbfifo.regs + LPBFIFO_REG_BYTES_DONE_STATUS);
        void __iomem *reg;
        u32 *data;
        int count, i;
        int do_callback = 0;
        u32 ts;
        unsigned long flags;
        int dma, write, poll_dma;

        spin_lock_irqsave(&lpbfifo.lock, flags);
        ts = mftb();

        req = lpbfifo.req;
        if (!req) {
                spin_unlock_irqrestore(&lpbfifo.lock, flags);
                pr_err("bogus LPBFIFO IRQ\n");
                return IRQ_HANDLED;
        }

        dma = !(req->flags & MPC52XX_LPBFIFO_FLAG_NO_DMA);
        write = req->flags & MPC52XX_LPBFIFO_FLAG_WRITE;
        poll_dma = req->flags & MPC52XX_LPBFIFO_FLAG_POLL_DMA;

        if (dma && !write) {
                spin_unlock_irqrestore(&lpbfifo.lock, flags);
                pr_err("bogus LPBFIFO IRQ (dma and not writing)\n");
                return IRQ_HANDLED;
        }

        if ((status & 0x01) == 0) {
                goto out;
        }

        /* check abort bit */
        if (status & 0x10) {
                out_be32(lpbfifo.regs + LPBFIFO_REG_ENABLE, 0x01010000);
                do_callback = 1;
                goto out;
        }

        /* Read result from hardware */
        count = in_be32(lpbfifo.regs + LPBFIFO_REG_BYTES_DONE_STATUS);
        count &= 0x00ffffff;

        if (!dma && !write) {
                /* copy the data out of the FIFO */
                reg = lpbfifo.regs + LPBFIFO_REG_FIFO_DATA;
                data = req->data + req->pos;
                for (i = 0; i < count; i += 4)
                        *data++ = in_be32(reg);
        }

        /* Update transfer position and count */
        req->pos += count;

        /* Decide what to do next */
        if (req->size - req->pos)
                mpc52xx_lpbfifo_kick(req); /* more work to do */
        else
                do_callback = 1;

 out:
        /* Clear the IRQ */
        out_8(lpbfifo.regs + LPBFIFO_REG_BYTES_DONE_STATUS, 0x01);

        if (dma && (status & 0x11)) {
                /*
                 * Count the DMA as complete only when the FIFO completion
                 * status or abort bits are set.
                 *
                 * (status & 0x01) should always be the case except sometimes
                 * when using polled DMA.
                 *
                 * (status & 0x10) {transfer aborted}: This case needs more
                 * testing.
                 */
                bcom_retrieve_buffer(lpbfifo.bcom_cur_task, &status, NULL);
        }
        req->last_byte = ((u8 *)req->data)[req->size - 1];

        /* When the do_callback flag is set; it means the transfer is finished
         * so set the FIFO as idle */
        if (do_callback)
                lpbfifo.req = NULL;

        if (irq != 0) /* don't increment on polled case */
                req->irq_count++;

        req->irq_ticks += mftb() - ts;
        spin_unlock_irqrestore(&lpbfifo.lock, flags);

        /* Spinlock is released; it is now safe to call the callback */
        if (do_callback && req->callback)
                req->callback(req);

        return IRQ_HANDLED;
}

/**
 * mpc52xx_lpbfifo_bcom_irq - IRQ handler for LPB FIFO Bestcomm task
 *
 * Only used when receiving data.
 */
static irqreturn_t mpc52xx_lpbfifo_bcom_irq(int irq, void *dev_id)
{
        struct mpc52xx_lpbfifo_request *req;
        unsigned long flags;
        u32 status;
        u32 ts;

        spin_lock_irqsave(&lpbfifo.lock, flags);
        ts = mftb();

        req = lpbfifo.req;
        if (!req || (req->flags & MPC52XX_LPBFIFO_FLAG_NO_DMA)) {
                spin_unlock_irqrestore(&lpbfifo.lock, flags);
                return IRQ_HANDLED;
        }

        if (irq != 0) /* don't increment on polled case */
                req->irq_count++;

        if (!bcom_buffer_done(lpbfifo.bcom_cur_task)) {
                spin_unlock_irqrestore(&lpbfifo.lock, flags);

                req->buffer_not_done_cnt++;
                if ((req->buffer_not_done_cnt % 1000) == 0)
                        pr_err("transfer stalled\n");

                return IRQ_HANDLED;
        }

        bcom_retrieve_buffer(lpbfifo.bcom_cur_task, &status, NULL);

        req->last_byte = ((u8 *)req->data)[req->size - 1];

        req->pos = status & 0x00ffffff;

        /* Mark the FIFO as idle */
        lpbfifo.req = NULL;

        /* Release the lock before calling out to the callback. */
        req->irq_ticks += mftb() - ts;
        spin_unlock_irqrestore(&lpbfifo.lock, flags);

        if (req->callback)
                req->callback(req);

        return IRQ_HANDLED;
}

/**
 * mpc52xx_lpbfifo_bcom_poll - Poll for DMA completion
 */
void mpc52xx_lpbfifo_poll(void)
{
        struct mpc52xx_lpbfifo_request *req = lpbfifo.req;
        int dma = !(req->flags & MPC52XX_LPBFIFO_FLAG_NO_DMA);
        int write = req->flags & MPC52XX_LPBFIFO_FLAG_WRITE;

        /*
         * For more information, see comments on the "Fat Lady" 
         */
        if (dma && write)
                mpc52xx_lpbfifo_irq(0, NULL);
        else 
                mpc52xx_lpbfifo_bcom_irq(0, NULL);
}
EXPORT_SYMBOL(mpc52xx_lpbfifo_poll);

/**
 * mpc52xx_lpbfifo_submit - Submit an LPB FIFO transfer request.
 * @req: Pointer to request structure
 */
int mpc52xx_lpbfifo_submit(struct mpc52xx_lpbfifo_request *req)
{
        unsigned long flags;

        if (!lpbfifo.regs)
                return -ENODEV;

        spin_lock_irqsave(&lpbfifo.lock, flags);

        /* If the req pointer is already set, then a transfer is in progress */
        if (lpbfifo.req) {
                spin_unlock_irqrestore(&lpbfifo.lock, flags);
                return -EBUSY;
        }

        /* Setup the transfer */
        lpbfifo.req = req;
        req->irq_count = 0;
        req->irq_ticks = 0;
        req->buffer_not_done_cnt = 0;
        req->pos = 0;

        mpc52xx_lpbfifo_kick(req);
        spin_unlock_irqrestore(&lpbfifo.lock, flags);
        return 0;
}
EXPORT_SYMBOL(mpc52xx_lpbfifo_submit);

int mpc52xx_lpbfifo_start_xfer(struct mpc52xx_lpbfifo_request *req)
{
        unsigned long flags;

        if (!lpbfifo.regs)
                return -ENODEV;

        spin_lock_irqsave(&lpbfifo.lock, flags);

        /*
         * If the req pointer is already set and a transfer was
         * started on submit, then this transfer is in progress
         */
        if (lpbfifo.req && !lpbfifo.req->defer_xfer_start) {
                spin_unlock_irqrestore(&lpbfifo.lock, flags);
                return -EBUSY;
        }

        /*
         * If the req was previously submitted but not
         * started, start it now
         */
        if (lpbfifo.req && lpbfifo.req == req &&
            lpbfifo.req->defer_xfer_start) {
                out_8(lpbfifo.regs + LPBFIFO_REG_PACKET_SIZE, 0x01);
        }

        spin_unlock_irqrestore(&lpbfifo.lock, flags);
        return 0;
}
EXPORT_SYMBOL(mpc52xx_lpbfifo_start_xfer);

void mpc52xx_lpbfifo_abort(struct mpc52xx_lpbfifo_request *req)
{
        unsigned long flags;

        spin_lock_irqsave(&lpbfifo.lock, flags);
        if (lpbfifo.req == req) {
                /* Put it into reset and clear the state */
                bcom_gen_bd_rx_reset(lpbfifo.bcom_rx_task);
                bcom_gen_bd_tx_reset(lpbfifo.bcom_tx_task);
                out_be32(lpbfifo.regs + LPBFIFO_REG_ENABLE, 0x01010000);
                lpbfifo.req = NULL;
        }
        spin_unlock_irqrestore(&lpbfifo.lock, flags);
}
EXPORT_SYMBOL(mpc52xx_lpbfifo_abort);

static int mpc52xx_lpbfifo_probe(struct platform_device *op)
{
        struct resource res;
        int rc = -ENOMEM;

        if (lpbfifo.dev != NULL)
                return -ENOSPC;

        lpbfifo.irq = irq_of_parse_and_map(op->dev.of_node, 0);
        if (!lpbfifo.irq)
                return -ENODEV;

        if (of_address_to_resource(op->dev.of_node, 0, &res))
                return -ENODEV;
        lpbfifo.regs_phys = res.start;
        lpbfifo.regs = of_iomap(op->dev.of_node, 0);
        if (!lpbfifo.regs)
                return -ENOMEM;

        spin_lock_init(&lpbfifo.lock);

        /* Put FIFO into reset */
        out_be32(lpbfifo.regs + LPBFIFO_REG_ENABLE, 0x01010000);

        /* Register the interrupt handler */
        rc = request_irq(lpbfifo.irq, mpc52xx_lpbfifo_irq, 0,
                         "mpc52xx-lpbfifo", &lpbfifo);
        if (rc)
                goto err_irq;

        /* Request the Bestcomm receive (fifo --> memory) task and IRQ */
        lpbfifo.bcom_rx_task =
                bcom_gen_bd_rx_init(2, res.start + LPBFIFO_REG_FIFO_DATA,
                                    BCOM_INITIATOR_SCLPC, BCOM_IPR_SCLPC,
                                    16*1024*1024);
        if (!lpbfifo.bcom_rx_task)
                goto err_bcom_rx;

        rc = request_irq(bcom_get_task_irq(lpbfifo.bcom_rx_task),
                         mpc52xx_lpbfifo_bcom_irq, 0,
                         "mpc52xx-lpbfifo-rx", &lpbfifo);
        if (rc)
                goto err_bcom_rx_irq;

        lpbfifo.dma_irqs_enabled = 1;

        /* Request the Bestcomm transmit (memory --> fifo) task and IRQ */
        lpbfifo.bcom_tx_task =
                bcom_gen_bd_tx_init(2, res.start + LPBFIFO_REG_FIFO_DATA,
                                    BCOM_INITIATOR_SCLPC, BCOM_IPR_SCLPC);
        if (!lpbfifo.bcom_tx_task)
                goto err_bcom_tx;

        lpbfifo.dev = &op->dev;
        return 0;

 err_bcom_tx:
        free_irq(bcom_get_task_irq(lpbfifo.bcom_rx_task), &lpbfifo);
 err_bcom_rx_irq:
        bcom_gen_bd_rx_release(lpbfifo.bcom_rx_task);
 err_bcom_rx:
 err_irq:
        iounmap(lpbfifo.regs);
        lpbfifo.regs = NULL;

        dev_err(&op->dev, "mpc52xx_lpbfifo_probe() failed\n");
        return -ENODEV;
}


static int mpc52xx_lpbfifo_remove(struct platform_device *op)
{
        if (lpbfifo.dev != &op->dev)
                return 0;

        /* Put FIFO in reset */
        out_be32(lpbfifo.regs + LPBFIFO_REG_ENABLE, 0x01010000);

        /* Release the bestcomm transmit task */
        free_irq(bcom_get_task_irq(lpbfifo.bcom_tx_task), &lpbfifo);
        bcom_gen_bd_tx_release(lpbfifo.bcom_tx_task);
        
        /* Release the bestcomm receive task */
        free_irq(bcom_get_task_irq(lpbfifo.bcom_rx_task), &lpbfifo);
        bcom_gen_bd_rx_release(lpbfifo.bcom_rx_task);

        free_irq(lpbfifo.irq, &lpbfifo);
        iounmap(lpbfifo.regs);
        lpbfifo.regs = NULL;
        lpbfifo.dev = NULL;

        return 0;
}

static const struct of_device_id mpc52xx_lpbfifo_match[] = {
        { .compatible = "fsl,mpc5200-lpbfifo", },
        {},
};
MODULE_DEVICE_TABLE(of, mpc52xx_lpbfifo_match);

static struct platform_driver mpc52xx_lpbfifo_driver = {
        .driver = {
                .name = "mpc52xx-lpbfifo",
                .of_match_table = mpc52xx_lpbfifo_match,
        },
        .probe = mpc52xx_lpbfifo_probe,
        .remove = mpc52xx_lpbfifo_remove,
};
module_platform_driver(mpc52xx_lpbfifo_driver);