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Commit dd6fd4a3 authored by Masahiro Yamada's avatar Masahiro Yamada Committed by Wolfram Sang
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i2c: uniphier: add UniPhier FIFO-less I2C driver 



Add support for on-chip I2C controller used on old UniPhier SoCs
such as PH1-LD4, PH1-sLD8, etc.  This adapter is so simple that
it has no FIFO in it.

Signed-off-by: default avatarMasahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: default avatarWolfram Sang <wsa@the-dreams.de>
parent 3eddad96

Documentation/devicetree/bindings/i2c/i2c-uniphier.txt

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UniPhier I2C controller (FIFO-less)



Required properties:

- compatible: should be "socionext,uniphier-i2c".

- #address-cells: should be 1.

- #size-cells: should be 0.

- reg: offset and length of the register set for the device.

- interrupts: a single interrupt specifier.

- clocks: phandle to the input clock.



Optional properties:

- clock-frequency: desired I2C bus frequency in Hz.  The maximum supported

  value is 400000.  Defaults to 100000 if not specified.



Examples:



	i2c0: i2c@58400000 {

		compatible = "socionext,uniphier-i2c";

		reg = <0x58400000 0x40>;

		#address-cells = <1>;

		#size-cells = <0>;

		interrupts = <0 41 1>;

		clocks = <&i2c_clk>;

		clock-frequency = <100000>;

	};

MAINTAINERS

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@@ -1607,6 +1607,7 @@ L: linux-arm-kernel@lists.infradead.org (moderated for non-subscribers) 
S:	Maintained

F:	arch/arm/boot/dts/uniphier*

F:	arch/arm/mach-uniphier/

F:	drivers/i2c/busses/i2c-uniphier*

F:	drivers/pinctrl/uniphier/

F:	drivers/tty/serial/8250/8250_uniphier.c

N:	uniphier

drivers/i2c/busses/Kconfig

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@@ -902,6 +902,14 @@ config I2C_TEGRA 
	  If you say yes to this option, support will be included for the

	  I2C controller embedded in NVIDIA Tegra SOCs



config I2C_UNIPHIER

	tristate "UniPhier FIFO-less I2C controller"

	depends on ARCH_UNIPHIER

	help

	  If you say yes to this option, support will be included for

	  the UniPhier FIFO-less I2C interface embedded in PH1-LD4, PH1-sLD8,

	  or older UniPhier SoCs.



config I2C_VERSATILE

	tristate "ARM Versatile/Realview I2C bus support"

	depends on ARCH_VERSATILE || ARCH_REALVIEW || ARCH_VEXPRESS

drivers/i2c/busses/Makefile

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@@ -87,6 +87,7 @@ obj-$(CONFIG_I2C_ST) += i2c-st.o 
obj-$(CONFIG_I2C_STU300)	+= i2c-stu300.o

obj-$(CONFIG_I2C_SUN6I_P2WI)	+= i2c-sun6i-p2wi.o

obj-$(CONFIG_I2C_TEGRA)		+= i2c-tegra.o

obj-$(CONFIG_I2C_UNIPHIER)	+= i2c-uniphier.o

obj-$(CONFIG_I2C_VERSATILE)	+= i2c-versatile.o

obj-$(CONFIG_I2C_WMT)		+= i2c-wmt.o

obj-$(CONFIG_I2C_OCTEON)	+= i2c-octeon.o

drivers/i2c/busses/i2c-uniphier.c

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/*

 * Copyright (C) 2015 Masahiro Yamada <yamada.masahiro@socionext.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 <linux/clk.h>

#include <linux/i2c.h>

#include <linux/interrupt.h>

#include <linux/io.h>

#include <linux/module.h>

#include <linux/platform_device.h>



#define UNIPHIER_I2C_DTRM	0x00	/* TX register */

#define     UNIPHIER_I2C_DTRM_IRQEN	BIT(11)	/* enable interrupt */

#define     UNIPHIER_I2C_DTRM_STA	BIT(10)	/* start condition */

#define     UNIPHIER_I2C_DTRM_STO	BIT(9)	/* stop condition */

#define     UNIPHIER_I2C_DTRM_NACK	BIT(8)	/* do not return ACK */

#define     UNIPHIER_I2C_DTRM_RD	BIT(0)	/* read transaction */

#define UNIPHIER_I2C_DREC	0x04	/* RX register */

#define     UNIPHIER_I2C_DREC_MST	BIT(14)	/* 1 = master, 0 = slave */

#define     UNIPHIER_I2C_DREC_TX	BIT(13)	/* 1 = transmit, 0 = receive */

#define     UNIPHIER_I2C_DREC_STS	BIT(12)	/* stop condition detected */

#define     UNIPHIER_I2C_DREC_LRB	BIT(11)	/* no ACK */

#define     UNIPHIER_I2C_DREC_LAB	BIT(9)	/* arbitration lost */

#define     UNIPHIER_I2C_DREC_BBN	BIT(8)	/* bus not busy */

#define UNIPHIER_I2C_MYAD	0x08	/* slave address */

#define UNIPHIER_I2C_CLK	0x0c	/* clock frequency control */

#define UNIPHIER_I2C_BRST	0x10	/* bus reset */

#define     UNIPHIER_I2C_BRST_FOEN	BIT(1)	/* normal operation */

#define     UNIPHIER_I2C_BRST_RSCL	BIT(0)	/* release SCL */

#define UNIPHIER_I2C_HOLD	0x14	/* hold time control */

#define UNIPHIER_I2C_BSTS	0x18	/* bus status monitor */

#define     UNIPHIER_I2C_BSTS_SDA	BIT(1)	/* readback of SDA line */

#define     UNIPHIER_I2C_BSTS_SCL	BIT(0)	/* readback of SCL line */

#define UNIPHIER_I2C_NOISE	0x1c	/* noise filter control */

#define UNIPHIER_I2C_SETUP	0x20	/* setup time control */



#define UNIPHIER_I2C_DEFAULT_SPEED	100000

#define UNIPHIER_I2C_MAX_SPEED		400000



struct uniphier_i2c_priv {

	struct completion comp;

	struct i2c_adapter adap;

	void __iomem *membase;

	struct clk *clk;

	unsigned int busy_cnt;

};



static irqreturn_t uniphier_i2c_interrupt(int irq, void *dev_id)

{

	struct uniphier_i2c_priv *priv = dev_id;



	/*

	 * This hardware uses edge triggered interrupt.  Do not touch the

	 * hardware registers in this handler to make sure to catch the next

	 * interrupt edge.  Just send a complete signal and return.

	 */

	complete(&priv->comp);



	return IRQ_HANDLED;

}



static int uniphier_i2c_xfer_byte(struct i2c_adapter *adap, u32 txdata,

				  u32 *rxdatap)

{

	struct uniphier_i2c_priv *priv = i2c_get_adapdata(adap);

	unsigned long time_left;

	u32 rxdata;



	reinit_completion(&priv->comp);



	txdata |= UNIPHIER_I2C_DTRM_IRQEN;

	dev_dbg(&adap->dev, "write data: 0x%04x\n", txdata);

	writel(txdata, priv->membase + UNIPHIER_I2C_DTRM);



	time_left = wait_for_completion_timeout(&priv->comp, adap->timeout);

	if (unlikely(!time_left)) {

		dev_err(&adap->dev, "transaction timeout\n");

		return -ETIMEDOUT;

	}



	rxdata = readl(priv->membase + UNIPHIER_I2C_DREC);

	dev_dbg(&adap->dev, "read data: 0x%04x\n", rxdata);



	if (rxdatap)

		*rxdatap = rxdata;



	return 0;

}



static int uniphier_i2c_send_byte(struct i2c_adapter *adap, u32 txdata)

{

	u32 rxdata;

	int ret;



	ret = uniphier_i2c_xfer_byte(adap, txdata, &rxdata);

	if (ret)

		return ret;



	if (unlikely(rxdata & UNIPHIER_I2C_DREC_LAB)) {

		dev_dbg(&adap->dev, "arbitration lost\n");

		return -EAGAIN;

	}

	if (unlikely(rxdata & UNIPHIER_I2C_DREC_LRB)) {

		dev_dbg(&adap->dev, "could not get ACK\n");

		return -ENXIO;

	}



	return 0;

}



static int uniphier_i2c_tx(struct i2c_adapter *adap, u16 addr, u16 len,

			   const u8 *buf)

{

	int ret;



	dev_dbg(&adap->dev, "start condition\n");

	ret = uniphier_i2c_send_byte(adap, addr << 1 |

				     UNIPHIER_I2C_DTRM_STA |

				     UNIPHIER_I2C_DTRM_NACK);

	if (ret)

		return ret;



	while (len--) {

		ret = uniphier_i2c_send_byte(adap,

					     UNIPHIER_I2C_DTRM_NACK | *buf++);

		if (ret)

			return ret;

	}



	return 0;

}



static int uniphier_i2c_rx(struct i2c_adapter *adap, u16 addr, u16 len,

			   u8 *buf)

{

	int ret;



	dev_dbg(&adap->dev, "start condition\n");

	ret = uniphier_i2c_send_byte(adap, addr << 1 |

				     UNIPHIER_I2C_DTRM_STA |

				     UNIPHIER_I2C_DTRM_NACK |

				     UNIPHIER_I2C_DTRM_RD);

	if (ret)

		return ret;



	while (len--) {

		u32 rxdata;



		ret = uniphier_i2c_xfer_byte(adap,

					     len ? 0 : UNIPHIER_I2C_DTRM_NACK,

					     &rxdata);

		if (ret)

			return ret;

		*buf++ = rxdata;

	}



	return 0;

}



static int uniphier_i2c_stop(struct i2c_adapter *adap)

{

	dev_dbg(&adap->dev, "stop condition\n");

	return uniphier_i2c_send_byte(adap, UNIPHIER_I2C_DTRM_STO |

				      UNIPHIER_I2C_DTRM_NACK);

}



static int uniphier_i2c_master_xfer_one(struct i2c_adapter *adap,

					struct i2c_msg *msg, bool stop)

{

	bool is_read = msg->flags & I2C_M_RD;

	bool recovery = false;

	int ret;



	dev_dbg(&adap->dev, "%s: addr=0x%02x, len=%d, stop=%d\n",

		is_read ? "receive" : "transmit", msg->addr, msg->len, stop);



	if (is_read)

		ret = uniphier_i2c_rx(adap, msg->addr, msg->len, msg->buf);

	else

		ret = uniphier_i2c_tx(adap, msg->addr, msg->len, msg->buf);



	if (ret == -EAGAIN) /* could not acquire bus. bail out without STOP */

		return ret;



	if (ret == -ETIMEDOUT) {

		/* This error is fatal.  Needs recovery. */

		stop = false;

		recovery = true;

	}



	if (stop) {

		int ret2 = uniphier_i2c_stop(adap);



		if (ret2) {

			/* Failed to issue STOP.  The bus needs recovery. */

			recovery = true;

			ret = ret ?: ret2;

		}

	}



	if (recovery)

		i2c_recover_bus(adap);



	return ret;

}



static int uniphier_i2c_check_bus_busy(struct i2c_adapter *adap)

{

	struct uniphier_i2c_priv *priv = i2c_get_adapdata(adap);



	if (!(readl(priv->membase + UNIPHIER_I2C_DREC) &

						UNIPHIER_I2C_DREC_BBN)) {

		if (priv->busy_cnt++ > 3) {

			/*

			 * If bus busy continues too long, it is probably

			 * in a wrong state.  Try bus recovery.

			 */

			i2c_recover_bus(adap);

			priv->busy_cnt = 0;

		}



		return -EAGAIN;

	}



	priv->busy_cnt = 0;

	return 0;

}



static int uniphier_i2c_master_xfer(struct i2c_adapter *adap,

				    struct i2c_msg *msgs, int num)

{

	struct i2c_msg *msg, *emsg = msgs + num;

	int ret;



	ret = uniphier_i2c_check_bus_busy(adap);

	if (ret)

		return ret;



	for (msg = msgs; msg < emsg; msg++) {

		/* If next message is read, skip the stop condition */

		bool stop = !(msg + 1 < emsg && msg[1].flags & I2C_M_RD);

		/* but, force it if I2C_M_STOP is set */

		if (msg->flags & I2C_M_STOP)

			stop = true;



		ret = uniphier_i2c_master_xfer_one(adap, msg, stop);

		if (ret)

			return ret;

	}



	return num;

}



static u32 uniphier_i2c_functionality(struct i2c_adapter *adap)

{

	return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;

}



static const struct i2c_algorithm uniphier_i2c_algo = {

	.master_xfer = uniphier_i2c_master_xfer,

	.functionality = uniphier_i2c_functionality,

};



static void uniphier_i2c_reset(struct uniphier_i2c_priv *priv, bool reset_on)

{

	u32 val = UNIPHIER_I2C_BRST_RSCL;



	val |= reset_on ? 0 : UNIPHIER_I2C_BRST_FOEN;

	writel(val, priv->membase + UNIPHIER_I2C_BRST);

}



static int uniphier_i2c_get_scl(struct i2c_adapter *adap)

{

	struct uniphier_i2c_priv *priv = i2c_get_adapdata(adap);



	return !!(readl(priv->membase + UNIPHIER_I2C_BSTS) &

							UNIPHIER_I2C_BSTS_SCL);

}



static void uniphier_i2c_set_scl(struct i2c_adapter *adap, int val)

{

	struct uniphier_i2c_priv *priv = i2c_get_adapdata(adap);



	writel(val ? UNIPHIER_I2C_BRST_RSCL : 0,

	       priv->membase + UNIPHIER_I2C_BRST);

}



static int uniphier_i2c_get_sda(struct i2c_adapter *adap)

{

	struct uniphier_i2c_priv *priv = i2c_get_adapdata(adap);



	return !!(readl(priv->membase + UNIPHIER_I2C_BSTS) &

							UNIPHIER_I2C_BSTS_SDA);

}



static void uniphier_i2c_unprepare_recovery(struct i2c_adapter *adap)

{

	uniphier_i2c_reset(i2c_get_adapdata(adap), false);

}



static struct i2c_bus_recovery_info uniphier_i2c_bus_recovery_info = {

	.recover_bus = i2c_generic_scl_recovery,

	.get_scl = uniphier_i2c_get_scl,

	.set_scl = uniphier_i2c_set_scl,

	.get_sda = uniphier_i2c_get_sda,

	.unprepare_recovery = uniphier_i2c_unprepare_recovery,

};



static int uniphier_i2c_clk_init(struct device *dev,

				 struct uniphier_i2c_priv *priv)

{

	struct device_node *np = dev->of_node;

	unsigned long clk_rate;

	u32 bus_speed;

	int ret;



	if (of_property_read_u32(np, "clock-frequency", &bus_speed))

		bus_speed = UNIPHIER_I2C_DEFAULT_SPEED;



	if (bus_speed > UNIPHIER_I2C_MAX_SPEED)

		bus_speed = UNIPHIER_I2C_MAX_SPEED;



	/* Get input clk rate through clk driver */

	priv->clk = devm_clk_get(dev, NULL);

	if (IS_ERR(priv->clk)) {

		dev_err(dev, "failed to get clock\n");

		return PTR_ERR(priv->clk);

	}



	ret = clk_prepare_enable(priv->clk);

	if (ret)

		return ret;



	clk_rate = clk_get_rate(priv->clk);



	uniphier_i2c_reset(priv, true);



	writel((clk_rate / bus_speed / 2 << 16) | (clk_rate / bus_speed),

	       priv->membase + UNIPHIER_I2C_CLK);



	uniphier_i2c_reset(priv, false);



	return 0;

}



static int uniphier_i2c_probe(struct platform_device *pdev)

{

	struct device *dev = &pdev->dev;

	struct uniphier_i2c_priv *priv;

	struct resource *regs;

	int irq;

	int ret;



	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);

	if (!priv)

		return -ENOMEM;



	regs = platform_get_resource(pdev, IORESOURCE_MEM, 0);

	priv->membase = devm_ioremap_resource(dev, regs);

	if (IS_ERR(priv->membase))

		return PTR_ERR(priv->membase);



	irq = platform_get_irq(pdev, 0);

	if (irq < 0) {

		dev_err(dev, "failed to get IRQ number");

		return irq;

	}



	init_completion(&priv->comp);

	priv->adap.owner = THIS_MODULE;

	priv->adap.algo = &uniphier_i2c_algo;

	priv->adap.dev.parent = dev;

	priv->adap.dev.of_node = dev->of_node;

	strlcpy(priv->adap.name, "UniPhier I2C", sizeof(priv->adap.name));

	priv->adap.bus_recovery_info = &uniphier_i2c_bus_recovery_info;

	i2c_set_adapdata(&priv->adap, priv);

	platform_set_drvdata(pdev, priv);



	ret = uniphier_i2c_clk_init(dev, priv);

	if (ret)

		return ret;



	ret = devm_request_irq(dev, irq, uniphier_i2c_interrupt, 0, pdev->name,

			       priv);

	if (ret) {

		dev_err(dev, "failed to request irq %d\n", irq);

		goto err;

	}



	ret = i2c_add_adapter(&priv->adap);

	if (ret) {

		dev_err(dev, "failed to add I2C adapter\n");

		goto err;

	}



err:

	if (ret)

		clk_disable_unprepare(priv->clk);



	return ret;

}



static int uniphier_i2c_remove(struct platform_device *pdev)

{

	struct uniphier_i2c_priv *priv = platform_get_drvdata(pdev);



	i2c_del_adapter(&priv->adap);

	clk_disable_unprepare(priv->clk);



	return 0;

}



static const struct of_device_id uniphier_i2c_match[] = {

	{ .compatible = "socionext,uniphier-i2c" },

	{ /* sentinel */ }

};

MODULE_DEVICE_TABLE(of, uniphier_i2c_match);



static struct platform_driver uniphier_i2c_drv = {

	.probe  = uniphier_i2c_probe,

	.remove = uniphier_i2c_remove,

	.driver = {

		.name  = "uniphier-i2c",

		.of_match_table = uniphier_i2c_match,

	},

};

module_platform_driver(uniphier_i2c_drv);



MODULE_AUTHOR("Masahiro Yamada <yamada.masahiro@socionext.com>");

MODULE_DESCRIPTION("UniPhier I2C bus driver");

MODULE_LICENSE("GPL");