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/* Copyright (c) 2009-2013, The Linux Foundation. All rights reserved.
 * Copyright (c) 2010, Google Inc.
 *
 * Original authors: Code Aurora Forum
 *
 * Author: Dima Zavin <dima@android.com>
 *  - Largely rewritten from original to not be an i2c driver.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 and
 * only version 2 as published by the Free Software Foundation.
 *
 * 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.
 */

#define pr_fmt(fmt) "%s: " fmt, __func__

#include <linux/delay.h>
#include <linux/err.h>
#include <linux/io.h>
#include <linux/kernel.h>
#include <linux/platform_device.h>
#include <linux/slab.h>
#include <linux/ssbi.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/of_device.h>

/* SSBI 2.0 controller registers */
#define SSBI2_CMD			0x0008
#define SSBI2_RD			0x0010
#define SSBI2_STATUS			0x0014
#define SSBI2_MODE2			0x001C

/* SSBI_CMD fields */
#define SSBI_CMD_RDWRN			(1 << 24)

/* SSBI_STATUS fields */
#define SSBI_STATUS_RD_READY		(1 << 2)
#define SSBI_STATUS_READY		(1 << 1)
#define SSBI_STATUS_MCHN_BUSY		(1 << 0)

/* SSBI_MODE2 fields */
#define SSBI_MODE2_REG_ADDR_15_8_SHFT	0x04
#define SSBI_MODE2_REG_ADDR_15_8_MASK	(0x7f << SSBI_MODE2_REG_ADDR_15_8_SHFT)

#define SET_SSBI_MODE2_REG_ADDR_15_8(MD, AD) \
	(((MD) & 0x0F) | ((((AD) >> 8) << SSBI_MODE2_REG_ADDR_15_8_SHFT) & \
	SSBI_MODE2_REG_ADDR_15_8_MASK))

/* SSBI PMIC Arbiter command registers */
#define SSBI_PA_CMD			0x0000
#define SSBI_PA_RD_STATUS		0x0004

/* SSBI_PA_CMD fields */
#define SSBI_PA_CMD_RDWRN		(1 << 24)
#define SSBI_PA_CMD_ADDR_MASK		0x7fff /* REG_ADDR_7_0, REG_ADDR_8_14*/

/* SSBI_PA_RD_STATUS fields */
#define SSBI_PA_RD_STATUS_TRANS_DONE	(1 << 27)
#define SSBI_PA_RD_STATUS_TRANS_DENIED	(1 << 26)

#define SSBI_TIMEOUT_US			100

enum ssbi_controller_type {
	MSM_SBI_CTRL_SSBI = 0,
	MSM_SBI_CTRL_SSBI2,
	MSM_SBI_CTRL_PMIC_ARBITER,
};

struct ssbi {
	struct device		*slave;
	void __iomem		*base;
	spinlock_t		lock;
	enum ssbi_controller_type controller_type;
	int (*read)(struct ssbi *, u16 addr, u8 *buf, int len);
	int (*write)(struct ssbi *, u16 addr, const u8 *buf, int len);
};

#define to_ssbi(dev)	platform_get_drvdata(to_platform_device(dev))

static inline u32 ssbi_readl(struct ssbi *ssbi, u32 reg)
{
	return readl(ssbi->base + reg);
}

static inline void ssbi_writel(struct ssbi *ssbi, u32 val, u32 reg)
{
	writel(val, ssbi->base + reg);
}

/*
 * Via private exchange with one of the original authors, the hardware
 * should generally finish a transaction in about 5us.  The worst
 * case, is when using the arbiter and both other CPUs have just
 * started trying to use the SSBI bus will result in a time of about
 * 20us.  It should never take longer than this.
 *
 * As such, this wait merely spins, with a udelay.
 */
static int ssbi_wait_mask(struct ssbi *ssbi, u32 set_mask, u32 clr_mask)
{
	u32 timeout = SSBI_TIMEOUT_US;
	u32 val;

	while (timeout--) {
		val = ssbi_readl(ssbi, SSBI2_STATUS);
		if (((val & set_mask) == set_mask) && ((val & clr_mask) == 0))
			return 0;
		udelay(1);
	}

	return -ETIMEDOUT;
}

static int
ssbi_read_bytes(struct ssbi *ssbi, u16 addr, u8 *buf, int len)
{
	u32 cmd = SSBI_CMD_RDWRN | ((addr & 0xff) << 16);
	int ret = 0;

	if (ssbi->controller_type == MSM_SBI_CTRL_SSBI2) {
		u32 mode2 = ssbi_readl(ssbi, SSBI2_MODE2);
		mode2 = SET_SSBI_MODE2_REG_ADDR_15_8(mode2, addr);
		ssbi_writel(ssbi, mode2, SSBI2_MODE2);
	}

	while (len) {
		ret = ssbi_wait_mask(ssbi, SSBI_STATUS_READY, 0);
		if (ret)
			goto err;

		ssbi_writel(ssbi, cmd, SSBI2_CMD);
		ret = ssbi_wait_mask(ssbi, SSBI_STATUS_RD_READY, 0);
		if (ret)
			goto err;
		*buf++ = ssbi_readl(ssbi, SSBI2_RD) & 0xff;
		len--;
	}

err:
	return ret;
}

static int
ssbi_write_bytes(struct ssbi *ssbi, u16 addr, const u8 *buf, int len)
{
	int ret = 0;

	if (ssbi->controller_type == MSM_SBI_CTRL_SSBI2) {
		u32 mode2 = ssbi_readl(ssbi, SSBI2_MODE2);
		mode2 = SET_SSBI_MODE2_REG_ADDR_15_8(mode2, addr);
		ssbi_writel(ssbi, mode2, SSBI2_MODE2);
	}

	while (len) {
		ret = ssbi_wait_mask(ssbi, SSBI_STATUS_READY, 0);
		if (ret)
			goto err;

		ssbi_writel(ssbi, ((addr & 0xff) << 16) | *buf, SSBI2_CMD);
		ret = ssbi_wait_mask(ssbi, 0, SSBI_STATUS_MCHN_BUSY);
		if (ret)
			goto err;
		buf++;
		len--;
	}

err:
	return ret;
}

/*
 * See ssbi_wait_mask for an explanation of the time and the
 * busywait.
 */
static inline int
ssbi_pa_transfer(struct ssbi *ssbi, u32 cmd, u8 *data)
{
	u32 timeout = SSBI_TIMEOUT_US;
	u32 rd_status = 0;

	ssbi_writel(ssbi, cmd, SSBI_PA_CMD);

	while (timeout--) {
		rd_status = ssbi_readl(ssbi, SSBI_PA_RD_STATUS);

		if (rd_status & SSBI_PA_RD_STATUS_TRANS_DENIED)
			return -EPERM;

		if (rd_status & SSBI_PA_RD_STATUS_TRANS_DONE) {
			if (data)
				*data = rd_status & 0xff;
			return 0;
		}
		udelay(1);
	}

	return -ETIMEDOUT;
}

static int
ssbi_pa_read_bytes(struct ssbi *ssbi, u16 addr, u8 *buf, int len)
{
	u32 cmd;
	int ret = 0;

	cmd = SSBI_PA_CMD_RDWRN | (addr & SSBI_PA_CMD_ADDR_MASK) << 8;

	while (len) {
		ret = ssbi_pa_transfer(ssbi, cmd, buf);
		if (ret)
			goto err;
		buf++;
		len--;
	}

err:
	return ret;
}

static int
ssbi_pa_write_bytes(struct ssbi *ssbi, u16 addr, const u8 *buf, int len)
{
	u32 cmd;
	int ret = 0;

	while (len) {
		cmd = (addr & SSBI_PA_CMD_ADDR_MASK) << 8 | *buf;
		ret = ssbi_pa_transfer(ssbi, cmd, NULL);
		if (ret)
			goto err;
		buf++;
		len--;
	}

err:
	return ret;
}

int ssbi_read(struct device *dev, u16 addr, u8 *buf, int len)
{
	struct ssbi *ssbi = to_ssbi(dev);
	unsigned long flags;
	int ret;

	spin_lock_irqsave(&ssbi->lock, flags);
	ret = ssbi->read(ssbi, addr, buf, len);
	spin_unlock_irqrestore(&ssbi->lock, flags);

	return ret;
}
EXPORT_SYMBOL_GPL(ssbi_read);

int ssbi_write(struct device *dev, u16 addr, const u8 *buf, int len)
{
	struct ssbi *ssbi = to_ssbi(dev);
	unsigned long flags;
	int ret;

	spin_lock_irqsave(&ssbi->lock, flags);
	ret = ssbi->write(ssbi, addr, buf, len);
	spin_unlock_irqrestore(&ssbi->lock, flags);

	return ret;
}
EXPORT_SYMBOL_GPL(ssbi_write);

static int ssbi_probe(struct platform_device *pdev)
{
	struct device_node *np = pdev->dev.of_node;
	struct resource *mem_res;
	struct ssbi *ssbi;
	const char *type;

	ssbi = devm_kzalloc(&pdev->dev, sizeof(*ssbi), GFP_KERNEL);
	if (!ssbi)
		return -ENOMEM;

	mem_res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
	ssbi->base = devm_ioremap_resource(&pdev->dev, mem_res);
	if (IS_ERR(ssbi->base))
		return PTR_ERR(ssbi->base);

	platform_set_drvdata(pdev, ssbi);

	type = of_get_property(np, "qcom,controller-type", NULL);
	if (type == NULL) {
		dev_err(&pdev->dev, "Missing qcom,controller-type property\n");
		return -EINVAL;
	}
	dev_info(&pdev->dev, "SSBI controller type: '%s'\n", type);
	if (strcmp(type, "ssbi") == 0)
		ssbi->controller_type = MSM_SBI_CTRL_SSBI;
	else if (strcmp(type, "ssbi2") == 0)
		ssbi->controller_type = MSM_SBI_CTRL_SSBI2;
	else if (strcmp(type, "pmic-arbiter") == 0)
		ssbi->controller_type = MSM_SBI_CTRL_PMIC_ARBITER;
	else {
		dev_err(&pdev->dev, "Unknown qcom,controller-type\n");
		return -EINVAL;
	}

	if (ssbi->controller_type == MSM_SBI_CTRL_PMIC_ARBITER) {
		ssbi->read = ssbi_pa_read_bytes;
		ssbi->write = ssbi_pa_write_bytes;
	} else {
		ssbi->read = ssbi_read_bytes;
		ssbi->write = ssbi_write_bytes;
	}

	spin_lock_init(&ssbi->lock);

	return of_platform_populate(np, NULL, NULL, &pdev->dev);
}

static const struct of_device_id ssbi_match_table[] = {
	{ .compatible = "qcom,ssbi" },
	{}
};
MODULE_DEVICE_TABLE(of, ssbi_match_table);

static struct platform_driver ssbi_driver = {
	.probe		= ssbi_probe,
	.driver		= {
		.name	= "ssbi",
		.of_match_table = ssbi_match_table,
	},
};
module_platform_driver(ssbi_driver);

MODULE_LICENSE("GPL v2");
MODULE_VERSION("1.0");
MODULE_ALIAS("platform:ssbi");
MODULE_AUTHOR("Dima Zavin <dima@android.com>");