/*
 * Core driver for the High Speed UART DMA
 *
 * Copyright (C) 2015 Intel Corporation
 * Author: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
 *
 * Partially based on the bits found in drivers/tty/serial/mfd.c.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

/*
 * DMA channel allocation:
 * 1. Even number chans are used for DMA Read (UART TX), odd chans for DMA
 *    Write (UART RX).
 * 2. 0/1 channel are assigned to port 0, 2/3 chan to port 1, 4/5 chan to
 *    port 3, and so on.
 */

#include <linux/delay.h>
#include <linux/dmaengine.h>
#include <linux/dma-mapping.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/slab.h>

#include "hsu.h"

#define HSU_DMA_BUSWIDTHS                               \
        BIT(DMA_SLAVE_BUSWIDTH_UNDEFINED)       |       \
        BIT(DMA_SLAVE_BUSWIDTH_1_BYTE)          |       \
        BIT(DMA_SLAVE_BUSWIDTH_2_BYTES)         |       \
        BIT(DMA_SLAVE_BUSWIDTH_3_BYTES)         |       \
        BIT(DMA_SLAVE_BUSWIDTH_4_BYTES)         |       \
        BIT(DMA_SLAVE_BUSWIDTH_8_BYTES)         |       \
        BIT(DMA_SLAVE_BUSWIDTH_16_BYTES)

static inline void hsu_chan_disable(struct hsu_dma_chan *hsuc)
{
        hsu_chan_writel(hsuc, HSU_CH_CR, 0);
}

static inline void hsu_chan_enable(struct hsu_dma_chan *hsuc)
{
        u32 cr = HSU_CH_CR_CHA;

        if (hsuc->direction == DMA_MEM_TO_DEV)
                cr &= ~HSU_CH_CR_CHD;
        else if (hsuc->direction == DMA_DEV_TO_MEM)
                cr |= HSU_CH_CR_CHD;

        hsu_chan_writel(hsuc, HSU_CH_CR, cr);
}

static void hsu_dma_chan_start(struct hsu_dma_chan *hsuc)
{
        struct dma_slave_config *config = &hsuc->config;
        struct hsu_dma_desc *desc = hsuc->desc;
        u32 bsr = 0, mtsr = 0;  /* to shut the compiler up */
        u32 dcr = HSU_CH_DCR_CHSOE | HSU_CH_DCR_CHEI;
        unsigned int i, count;

        if (hsuc->direction == DMA_MEM_TO_DEV) {
                bsr = config->dst_maxburst;
                mtsr = config->src_addr_width;
        } else if (hsuc->direction == DMA_DEV_TO_MEM) {
                bsr = config->src_maxburst;
                mtsr = config->dst_addr_width;
        }

        hsu_chan_disable(hsuc);

        hsu_chan_writel(hsuc, HSU_CH_DCR, 0);
        hsu_chan_writel(hsuc, HSU_CH_BSR, bsr);
        hsu_chan_writel(hsuc, HSU_CH_MTSR, mtsr);

        /* Set descriptors */
        count = desc->nents - desc->active;
        for (i = 0; i < count && i < HSU_DMA_CHAN_NR_DESC; i++) {
                hsu_chan_writel(hsuc, HSU_CH_DxSAR(i), desc->sg[i].addr);
                hsu_chan_writel(hsuc, HSU_CH_DxTSR(i), desc->sg[i].len);

                /* Prepare value for DCR */
                dcr |= HSU_CH_DCR_DESCA(i);
                dcr |= HSU_CH_DCR_CHTOI(i);     /* timeout bit, see HSU Errata 1 */

                desc->active++;
        }
        /* Only for the last descriptor in the chain */
        dcr |= HSU_CH_DCR_CHSOD(count - 1);
        dcr |= HSU_CH_DCR_CHDI(count - 1);

        hsu_chan_writel(hsuc, HSU_CH_DCR, dcr);

        hsu_chan_enable(hsuc);
}

static void hsu_dma_stop_channel(struct hsu_dma_chan *hsuc)
{
        hsu_chan_disable(hsuc);
        hsu_chan_writel(hsuc, HSU_CH_DCR, 0);
}

static void hsu_dma_start_channel(struct hsu_dma_chan *hsuc)
{
        hsu_dma_chan_start(hsuc);
}

static void hsu_dma_start_transfer(struct hsu_dma_chan *hsuc)
{
        struct virt_dma_desc *vdesc;

        /* Get the next descriptor */
        vdesc = vchan_next_desc(&hsuc->vchan);
        if (!vdesc) {
                hsuc->desc = NULL;
                return;
        }

        list_del(&vdesc->node);
        hsuc->desc = to_hsu_dma_desc(vdesc);

        /* Start the channel with a new descriptor */
        hsu_dma_start_channel(hsuc);
}

/*
 *      hsu_dma_get_status() - get DMA channel status
 *      @chip: HSUART DMA chip
 *      @nr: DMA channel number
 *      @status: pointer for DMA Channel Status Register value
 *
 *      Description:
 *      The function reads and clears the DMA Channel Status Register, checks
 *      if it was a timeout interrupt and returns a corresponding value.
 *
 *      Caller should provide a valid pointer for the DMA Channel Status
 *      Register value that will be returned in @status.
 *
 *      Return:
 *      1 for DMA timeout status, 0 for other DMA status, or error code for
 *      invalid parameters or no interrupt pending.
 */
int hsu_dma_get_status(struct hsu_dma_chip *chip, unsigned short nr,
                       u32 *status)
{
        struct hsu_dma_chan *hsuc;
        unsigned long flags;
        u32 sr;

        /* Sanity check */
        if (nr >= chip->hsu->nr_channels)
                return -EINVAL;

        hsuc = &chip->hsu->chan[nr];

        /*
         * No matter what situation, need read clear the IRQ status
         * There is a bug, see Errata 5, HSD 2900918
         */
        spin_lock_irqsave(&hsuc->vchan.lock, flags);
        sr = hsu_chan_readl(hsuc, HSU_CH_SR);
        spin_unlock_irqrestore(&hsuc->vchan.lock, flags);

        /* Check if any interrupt is pending */
        sr &= ~(HSU_CH_SR_DESCE_ANY | HSU_CH_SR_CDESC_ANY);
        if (!sr)
                return -EIO;

        /* Timeout IRQ, need wait some time, see Errata 2 */
        if (sr & HSU_CH_SR_DESCTO_ANY)
                udelay(2);

        /*
         * At this point, at least one of Descriptor Time Out, Channel Error
         * or Descriptor Done bits must be set. Clear the Descriptor Time Out
         * bits and if sr is still non-zero, it must be channel error or
         * descriptor done which are higher priority than timeout and handled
         * in hsu_dma_do_irq(). Else, it must be a timeout.
         */
        sr &= ~HSU_CH_SR_DESCTO_ANY;

        *status = sr;

        return sr ? 0 : 1;
}
EXPORT_SYMBOL_GPL(hsu_dma_get_status);

/*
 *      hsu_dma_do_irq() - DMA interrupt handler
 *      @chip: HSUART DMA chip
 *      @nr: DMA channel number
 *      @status: Channel Status Register value
 *
 *      Description:
 *      This function handles Channel Error and Descriptor Done interrupts.
 *      This function should be called after determining that the DMA interrupt
 *      is not a normal timeout interrupt, ie. hsu_dma_get_status() returned 0.
 *
 *      Return:
 *      0 for invalid channel number, 1 otherwise.
 */
int hsu_dma_do_irq(struct hsu_dma_chip *chip, unsigned short nr, u32 status)
{
        struct hsu_dma_chan *hsuc;
        struct hsu_dma_desc *desc;
        unsigned long flags;

        /* Sanity check */
        if (nr >= chip->hsu->nr_channels)
                return 0;

        hsuc = &chip->hsu->chan[nr];

        spin_lock_irqsave(&hsuc->vchan.lock, flags);
        desc = hsuc->desc;
        if (desc) {
                if (status & HSU_CH_SR_CHE) {
                        desc->status = DMA_ERROR;
                } else if (desc->active < desc->nents) {
                        hsu_dma_start_channel(hsuc);
                } else {
                        vchan_cookie_complete(&desc->vdesc);
                        desc->status = DMA_COMPLETE;
                        hsu_dma_start_transfer(hsuc);
                }
        }
        spin_unlock_irqrestore(&hsuc->vchan.lock, flags);

        return 1;
}
EXPORT_SYMBOL_GPL(hsu_dma_do_irq);

static struct hsu_dma_desc *hsu_dma_alloc_desc(unsigned int nents)
{
        struct hsu_dma_desc *desc;

        desc = kzalloc(sizeof(*desc), GFP_NOWAIT);
        if (!desc)
                return NULL;

        desc->sg = kcalloc(nents, sizeof(*desc->sg), GFP_NOWAIT);
        if (!desc->sg) {
                kfree(desc);
                return NULL;
        }

        return desc;
}

static void hsu_dma_desc_free(struct virt_dma_desc *vdesc)
{
        struct hsu_dma_desc *desc = to_hsu_dma_desc(vdesc);

        kfree(desc->sg);
        kfree(desc);
}

static struct dma_async_tx_descriptor *hsu_dma_prep_slave_sg(
                struct dma_chan *chan, struct scatterlist *sgl,
                unsigned int sg_len, enum dma_transfer_direction direction,
                unsigned long flags, void *context)
{
        struct hsu_dma_chan *hsuc = to_hsu_dma_chan(chan);
        struct hsu_dma_desc *desc;
        struct scatterlist *sg;
        unsigned int i;

        desc = hsu_dma_alloc_desc(sg_len);
        if (!desc)
                return NULL;

        for_each_sg(sgl, sg, sg_len, i) {
                desc->sg[i].addr = sg_dma_address(sg);
                desc->sg[i].len = sg_dma_len(sg);

                desc->length += sg_dma_len(sg);
        }

        desc->nents = sg_len;
        desc->direction = direction;
        /* desc->active = 0 by kzalloc */
        desc->status = DMA_IN_PROGRESS;

        return vchan_tx_prep(&hsuc->vchan, &desc->vdesc, flags);
}

static void hsu_dma_issue_pending(struct dma_chan *chan)
{
        struct hsu_dma_chan *hsuc = to_hsu_dma_chan(chan);
        unsigned long flags;

        spin_lock_irqsave(&hsuc->vchan.lock, flags);
        if (vchan_issue_pending(&hsuc->vchan) && !hsuc->desc)
                hsu_dma_start_transfer(hsuc);
        spin_unlock_irqrestore(&hsuc->vchan.lock, flags);
}

static size_t hsu_dma_active_desc_size(struct hsu_dma_chan *hsuc)
{
        struct hsu_dma_desc *desc = hsuc->desc;
        size_t bytes = 0;
        int i;

        for (i = desc->active; i < desc->nents; i++)
                bytes += desc->sg[i].len;

        i = HSU_DMA_CHAN_NR_DESC - 1;
        do {
                bytes += hsu_chan_readl(hsuc, HSU_CH_DxTSR(i));
        } while (--i >= 0);

        return bytes;
}

static enum dma_status hsu_dma_tx_status(struct dma_chan *chan,
        dma_cookie_t cookie, struct dma_tx_state *state)
{
        struct hsu_dma_chan *hsuc = to_hsu_dma_chan(chan);
        struct virt_dma_desc *vdesc;
        enum dma_status status;
        size_t bytes;
        unsigned long flags;

        status = dma_cookie_status(chan, cookie, state);
        if (status == DMA_COMPLETE)
                return status;

        spin_lock_irqsave(&hsuc->vchan.lock, flags);
        vdesc = vchan_find_desc(&hsuc->vchan, cookie);
        if (hsuc->desc && cookie == hsuc->desc->vdesc.tx.cookie) {
                bytes = hsu_dma_active_desc_size(hsuc);
                dma_set_residue(state, bytes);
                status = hsuc->desc->status;
        } else if (vdesc) {
                bytes = to_hsu_dma_desc(vdesc)->length;
                dma_set_residue(state, bytes);
        }
        spin_unlock_irqrestore(&hsuc->vchan.lock, flags);

        return status;
}

static int hsu_dma_slave_config(struct dma_chan *chan,
                                struct dma_slave_config *config)
{
        struct hsu_dma_chan *hsuc = to_hsu_dma_chan(chan);

        /* Check if chan will be configured for slave transfers */
        if (!is_slave_direction(config->direction))
                return -EINVAL;

        memcpy(&hsuc->config, config, sizeof(hsuc->config));

        return 0;
}

static int hsu_dma_pause(struct dma_chan *chan)
{
        struct hsu_dma_chan *hsuc = to_hsu_dma_chan(chan);
        unsigned long flags;

        spin_lock_irqsave(&hsuc->vchan.lock, flags);
        if (hsuc->desc && hsuc->desc->status == DMA_IN_PROGRESS) {
                hsu_chan_disable(hsuc);
                hsuc->desc->status = DMA_PAUSED;
        }
        spin_unlock_irqrestore(&hsuc->vchan.lock, flags);

        return 0;
}

static int hsu_dma_resume(struct dma_chan *chan)
{
        struct hsu_dma_chan *hsuc = to_hsu_dma_chan(chan);
        unsigned long flags;

        spin_lock_irqsave(&hsuc->vchan.lock, flags);
        if (hsuc->desc && hsuc->desc->status == DMA_PAUSED) {
                hsuc->desc->status = DMA_IN_PROGRESS;
                hsu_chan_enable(hsuc);
        }
        spin_unlock_irqrestore(&hsuc->vchan.lock, flags);

        return 0;
}

static int hsu_dma_terminate_all(struct dma_chan *chan)
{
        struct hsu_dma_chan *hsuc = to_hsu_dma_chan(chan);
        unsigned long flags;
        LIST_HEAD(head);

        spin_lock_irqsave(&hsuc->vchan.lock, flags);

        hsu_dma_stop_channel(hsuc);
        if (hsuc->desc) {
                hsu_dma_desc_free(&hsuc->desc->vdesc);
                hsuc->desc = NULL;
        }

        vchan_get_all_descriptors(&hsuc->vchan, &head);
        spin_unlock_irqrestore(&hsuc->vchan.lock, flags);
        vchan_dma_desc_free_list(&hsuc->vchan, &head);

        return 0;
}

static void hsu_dma_free_chan_resources(struct dma_chan *chan)
{
        vchan_free_chan_resources(to_virt_chan(chan));
}

int hsu_dma_probe(struct hsu_dma_chip *chip)
{
        struct hsu_dma *hsu;
        void __iomem *addr = chip->regs + chip->offset;
        unsigned short i;
        int ret;

        hsu = devm_kzalloc(chip->dev, sizeof(*hsu), GFP_KERNEL);
        if (!hsu)
                return -ENOMEM;

        chip->hsu = hsu;

        /* Calculate nr_channels from the IO space length */
        hsu->nr_channels = (chip->length - chip->offset) / HSU_DMA_CHAN_LENGTH;

        hsu->chan = devm_kcalloc(chip->dev, hsu->nr_channels,
                                 sizeof(*hsu->chan), GFP_KERNEL);
        if (!hsu->chan)
                return -ENOMEM;

        INIT_LIST_HEAD(&hsu->dma.channels);
        for (i = 0; i < hsu->nr_channels; i++) {
                struct hsu_dma_chan *hsuc = &hsu->chan[i];

                hsuc->vchan.desc_free = hsu_dma_desc_free;
                vchan_init(&hsuc->vchan, &hsu->dma);

                hsuc->direction = (i & 0x1) ? DMA_DEV_TO_MEM : DMA_MEM_TO_DEV;
                hsuc->reg = addr + i * HSU_DMA_CHAN_LENGTH;
        }

        dma_cap_set(DMA_SLAVE, hsu->dma.cap_mask);
        dma_cap_set(DMA_PRIVATE, hsu->dma.cap_mask);

        hsu->dma.device_free_chan_resources = hsu_dma_free_chan_resources;

        hsu->dma.device_prep_slave_sg = hsu_dma_prep_slave_sg;

        hsu->dma.device_issue_pending = hsu_dma_issue_pending;
        hsu->dma.device_tx_status = hsu_dma_tx_status;

        hsu->dma.device_config = hsu_dma_slave_config;
        hsu->dma.device_pause = hsu_dma_pause;
        hsu->dma.device_resume = hsu_dma_resume;
        hsu->dma.device_terminate_all = hsu_dma_terminate_all;

        hsu->dma.src_addr_widths = HSU_DMA_BUSWIDTHS;
        hsu->dma.dst_addr_widths = HSU_DMA_BUSWIDTHS;
        hsu->dma.directions = BIT(DMA_DEV_TO_MEM) | BIT(DMA_MEM_TO_DEV);
        hsu->dma.residue_granularity = DMA_RESIDUE_GRANULARITY_BURST;

        hsu->dma.dev = chip->dev;

        dma_set_max_seg_size(hsu->dma.dev, HSU_CH_DxTSR_MASK);

        ret = dma_async_device_register(&hsu->dma);
        if (ret)
                return ret;

        dev_info(chip->dev, "Found HSU DMA, %d channels\n", hsu->nr_channels);
        return 0;
}
EXPORT_SYMBOL_GPL(hsu_dma_probe);

int hsu_dma_remove(struct hsu_dma_chip *chip)
{
        struct hsu_dma *hsu = chip->hsu;
        unsigned short i;

        dma_async_device_unregister(&hsu->dma);

        for (i = 0; i < hsu->nr_channels; i++) {
                struct hsu_dma_chan *hsuc = &hsu->chan[i];

                tasklet_kill(&hsuc->vchan.task);
        }

        return 0;
}
EXPORT_SYMBOL_GPL(hsu_dma_remove);

MODULE_LICENSE("GPL v2");
MODULE_DESCRIPTION("High Speed UART DMA core driver");
MODULE_AUTHOR("Andy Shevchenko <andriy.shevchenko@linux.intel.com>");