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 * 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));
}

static void hsu_dma_synchronize(struct dma_chan *chan)
{
	struct hsu_dma_chan *hsuc = to_hsu_dma_chan(chan);

	vchan_synchronize(&hsuc->vchan);
}

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.device_synchronize = hsu_dma_synchronize;

	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>"