From af4e8a3c7b645480f57ec14ded02fba6976ff2d5 Mon Sep 17 00:00:00 2001
From: popcornmix <popcornmix@gmail.com>
Date: Wed, 17 Jun 2015 15:44:08 +0100
Subject: [PATCH] Add Chris Boot's i2c driver
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

i2c-bcm2708: fixed baudrate

Fixed issue where the wrong CDIV value was set for baudrates below 3815 Hz (for 250MHz bus clock).
In that case the computed CDIV value was more than 0xffff. However the CDIV register width is only 16 bits.
This resulted in incorrect setting of CDIV and higher baudrate than intended.
Example: 3500Hz -> CDIV=0x11704 -> CDIV(16bit)=0x1704 -> 42430Hz
After correction: 3500Hz -> CDIV=0x11704 -> CDIV(16bit)=0xffff -> 3815Hz
The correct baudrate is shown in the log after the cdiv > 0xffff correction.

Perform I2C combined transactions when possible

Perform I2C combined transactions whenever possible, within the
restrictions of the Broadcomm Serial Controller.

Disable DONE interrupt during TA poll

Prevent interrupt from being triggered if poll is missed and transfer
starts and finishes.

i2c: Make combined transactions optional and disabled by default

i2c: bcm2708: add device tree support

Add DT support to driver and add to .dtsi file.
Setup pins in .dts file.
i2c is disabled by default.

Signed-off-by: Noralf Tronnes <notro@tronnes.org>

bcm2708: don't register i2c controllers when using DT

The devices for the i2c controllers are in the Device Tree.
Only register devices when not using DT.

Signed-off-by: Noralf Tronnes <notro@tronnes.org>

I2C: Only register the I2C device for the current board revision

i2c_bcm2708: Fix clock reference counting

Fix grabbing lock from atomic context in i2c driver

2 main changes:
- check for timeouts in the bcm2708_bsc_setup function as indicated by this comment:
      /* poll for transfer start bit (should only take 1-20 polls) */
  This implies that the setup function can now fail so account for this everywhere it's called
- Removed the clk_get_rate call from inside the setup function as it locks a mutex and that's not ok since we call it from under a spin lock.

i2c-bcm2708: When using DT, leave the GPIO setup to pinctrl

i2c-bcm2708: Increase timeouts to allow larger transfers

Use the timeout value provided by the I2C_TIMEOUT ioctl when waiting
for completion. The default timeout is 1 second.

See: https://github.com/raspberrypi/linux/issues/260

i2c-bcm2708/BCM270X_DT: Add support for I2C2

The third I2C bus (I2C2) is normally reserved for HDMI use. Careless
use of this bus can break an attached display - use with caution.

It is recommended to disable accesses by VideoCore by setting
hdmi_ignore_edid=1 or hdmi_edid_file=1 in config.txt.

The interface is disabled by default - enable using the
i2c2_iknowwhatimdoing DT parameter.

bcm2708-spi: Don't use static pin configuration with DT

Also remove superfluous error checking - the SPI framework ensures the
validity of the chip_select value.

i2c-bcm2708: Remove non-DT support

Signed-off-by: Noralf Trønnes <noralf@tronnes.org>

Set the BSC_CLKT clock streching timeout to 35ms as per SMBus specs.

Fixes i2c_bcm2708: Write to FIFO correctly - v2 (#1574)

* i2c: fix i2c_bcm2708: Clear FIFO before sending data

Make sure FIFO gets cleared before trying to send
data in case of a repeated start (COMBINED=Y).

* i2c: fix i2c_bcm2708: Only write to FIFO when not full

Check if FIFO can accept data before writing.
To avoid a peripheral read on the last iteration of a loop,
both bcm2708_bsc_fifo_fill and ~drain are changed as well.
---
 drivers/i2c/busses/Kconfig       |  19 ++
 drivers/i2c/busses/Makefile      |   2 +
 drivers/i2c/busses/i2c-bcm2708.c | 512 +++++++++++++++++++++++++++++++++++++++
 3 files changed, 533 insertions(+)
 create mode 100644 drivers/i2c/busses/i2c-bcm2708.c

--- a/drivers/i2c/busses/Kconfig
+++ b/drivers/i2c/busses/Kconfig
@@ -8,6 +8,25 @@ menu "I2C Hardware Bus support"
 comment "PC SMBus host controller drivers"
 	depends on PCI
 
+config I2C_BCM2708
+	tristate "BCM2708 BSC"
+	depends on ARCH_BCM2835
+	help
+	  Enabling this option will add BSC (Broadcom Serial Controller)
+	  support for the BCM2708. BSC is a Broadcom proprietary bus compatible
+	  with I2C/TWI/SMBus.
+
+config I2C_BCM2708_BAUDRATE
+	prompt "BCM2708 I2C baudrate"
+	depends on I2C_BCM2708
+	int
+	default 100000
+	help
+	  Set the I2C baudrate. This will alter the default value. A
+	  different baudrate can be set by using a module parameter as well. If
+	  no parameter is provided when loading, this is the value that will be
+	  used.
+
 config I2C_ALI1535
 	tristate "ALI 1535"
 	depends on PCI
--- a/drivers/i2c/busses/Makefile
+++ b/drivers/i2c/busses/Makefile
@@ -2,6 +2,8 @@
 # Makefile for the i2c bus drivers.
 #
 
+obj-$(CONFIG_I2C_BCM2708)	+= i2c-bcm2708.o
+
 # ACPI drivers
 obj-$(CONFIG_I2C_SCMI)		+= i2c-scmi.o
 
--- /dev/null
+++ b/drivers/i2c/busses/i2c-bcm2708.c
@@ -0,0 +1,512 @@
+/*
+ * Driver for Broadcom BCM2708 BSC Controllers
+ *
+ * Copyright (C) 2012 Chris Boot & Frank Buss
+ *
+ * This driver is inspired by:
+ * i2c-ocores.c, by Peter Korsgaard <jacmet@sunsite.dk>
+ *
+ * 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.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/spinlock.h>
+#include <linux/clk.h>
+#include <linux/err.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/io.h>
+#include <linux/slab.h>
+#include <linux/i2c.h>
+#include <linux/interrupt.h>
+#include <linux/sched.h>
+#include <linux/wait.h>
+
+/* BSC register offsets */
+#define BSC_C			0x00
+#define BSC_S			0x04
+#define BSC_DLEN		0x08
+#define BSC_A			0x0c
+#define BSC_FIFO		0x10
+#define BSC_DIV			0x14
+#define BSC_DEL			0x18
+#define BSC_CLKT		0x1c
+
+/* Bitfields in BSC_C */
+#define BSC_C_I2CEN		0x00008000
+#define BSC_C_INTR		0x00000400
+#define BSC_C_INTT		0x00000200
+#define BSC_C_INTD		0x00000100
+#define BSC_C_ST		0x00000080
+#define BSC_C_CLEAR_1		0x00000020
+#define BSC_C_CLEAR_2		0x00000010
+#define BSC_C_READ		0x00000001
+
+/* Bitfields in BSC_S */
+#define BSC_S_CLKT		0x00000200
+#define BSC_S_ERR		0x00000100
+#define BSC_S_RXF		0x00000080
+#define BSC_S_TXE		0x00000040
+#define BSC_S_RXD		0x00000020
+#define BSC_S_TXD		0x00000010
+#define BSC_S_RXR		0x00000008
+#define BSC_S_TXW		0x00000004
+#define BSC_S_DONE		0x00000002
+#define BSC_S_TA		0x00000001
+
+#define I2C_WAIT_LOOP_COUNT	200
+
+#define DRV_NAME		"bcm2708_i2c"
+
+static unsigned int baudrate;
+module_param(baudrate, uint, S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP);
+MODULE_PARM_DESC(baudrate, "The I2C baudrate");
+
+static bool combined = false;
+module_param(combined, bool, 0644);
+MODULE_PARM_DESC(combined, "Use combined transactions");
+
+struct bcm2708_i2c {
+	struct i2c_adapter adapter;
+
+	spinlock_t lock;
+	void __iomem *base;
+	int irq;
+	struct clk *clk;
+	u32 cdiv;
+	u32 clk_tout;
+
+	struct completion done;
+
+	struct i2c_msg *msg;
+	int pos;
+	int nmsgs;
+	bool error;
+};
+
+static inline u32 bcm2708_rd(struct bcm2708_i2c *bi, unsigned reg)
+{
+	return readl(bi->base + reg);
+}
+
+static inline void bcm2708_wr(struct bcm2708_i2c *bi, unsigned reg, u32 val)
+{
+	writel(val, bi->base + reg);
+}
+
+static inline void bcm2708_bsc_reset(struct bcm2708_i2c *bi)
+{
+	bcm2708_wr(bi, BSC_C, 0);
+	bcm2708_wr(bi, BSC_S, BSC_S_CLKT | BSC_S_ERR | BSC_S_DONE);
+}
+
+static inline void bcm2708_bsc_fifo_drain(struct bcm2708_i2c *bi)
+{
+	while ((bi->pos < bi->msg->len) && (bcm2708_rd(bi, BSC_S) & BSC_S_RXD))
+		bi->msg->buf[bi->pos++] = bcm2708_rd(bi, BSC_FIFO);
+}
+
+static inline void bcm2708_bsc_fifo_fill(struct bcm2708_i2c *bi)
+{
+	while ((bi->pos < bi->msg->len) && (bcm2708_rd(bi, BSC_S) & BSC_S_TXD))
+		bcm2708_wr(bi, BSC_FIFO, bi->msg->buf[bi->pos++]);
+}
+
+static inline int bcm2708_bsc_setup(struct bcm2708_i2c *bi)
+{
+	u32 cdiv, s, clk_tout;
+	u32 c = BSC_C_I2CEN | BSC_C_INTD | BSC_C_ST | BSC_C_CLEAR_1;
+	int wait_loops = I2C_WAIT_LOOP_COUNT;
+
+	/* Can't call clk_get_rate as it locks a mutex and here we are spinlocked.
+	 * Use the value that we cached in the probe.
+	 */
+	cdiv = bi->cdiv;
+	clk_tout = bi->clk_tout;
+
+	if (bi->msg->flags & I2C_M_RD)
+		c |= BSC_C_INTR | BSC_C_READ;
+	else
+		c |= BSC_C_INTT;
+
+	bcm2708_wr(bi, BSC_CLKT, clk_tout);
+	bcm2708_wr(bi, BSC_DIV, cdiv);
+	bcm2708_wr(bi, BSC_A, bi->msg->addr);
+	bcm2708_wr(bi, BSC_DLEN, bi->msg->len);
+	if (combined)
+	{
+		/* Do the next two messages meet combined transaction criteria?
+		   - Current message is a write, next message is a read
+		   - Both messages to same slave address
+		   - Write message can fit inside FIFO (16 bytes or less) */
+		if ( (bi->nmsgs > 1) &&
+			!(bi->msg[0].flags & I2C_M_RD) && (bi->msg[1].flags & I2C_M_RD) &&
+			 (bi->msg[0].addr == bi->msg[1].addr) && (bi->msg[0].len <= 16)) {
+
+			/* Clear FIFO */
+			bcm2708_wr(bi, BSC_C, BSC_C_CLEAR_1);
+
+			/* Fill FIFO with entire write message (16 byte FIFO) */
+			while (bi->pos < bi->msg->len) {
+				bcm2708_wr(bi, BSC_FIFO, bi->msg->buf[bi->pos++]);
+			}
+			/* Start write transfer (no interrupts, don't clear FIFO) */
+			bcm2708_wr(bi, BSC_C, BSC_C_I2CEN | BSC_C_ST);
+
+			/* poll for transfer start bit (should only take 1-20 polls) */
+			do {
+				s = bcm2708_rd(bi, BSC_S);
+			} while (!(s & (BSC_S_TA | BSC_S_ERR | BSC_S_CLKT | BSC_S_DONE)) && --wait_loops >= 0);
+
+			/* did we time out or some error occured? */
+			if (wait_loops < 0 || (s & (BSC_S_ERR | BSC_S_CLKT))) {
+				return -1;
+			}
+
+			/* Send next read message before the write transfer finishes. */
+			bi->nmsgs--;
+			bi->msg++;
+			bi->pos = 0;
+			bcm2708_wr(bi, BSC_DLEN, bi->msg->len);
+			c = BSC_C_I2CEN | BSC_C_INTD | BSC_C_INTR | BSC_C_ST | BSC_C_READ;
+		}
+	}
+	bcm2708_wr(bi, BSC_C, c);
+
+	return 0;
+}
+
+static irqreturn_t bcm2708_i2c_interrupt(int irq, void *dev_id)
+{
+	struct bcm2708_i2c *bi = dev_id;
+	bool handled = true;
+	u32 s;
+	int ret;
+
+	spin_lock(&bi->lock);
+
+	/* we may see camera interrupts on the "other" I2C channel
+		   Just return if we've not sent anything */
+	if (!bi->nmsgs || !bi->msg) {
+		goto early_exit;
+	}
+
+	s = bcm2708_rd(bi, BSC_S);
+
+	if (s & (BSC_S_CLKT | BSC_S_ERR)) {
+		bcm2708_bsc_reset(bi);
+		bi->error = true;
+
+		bi->msg = 0; /* to inform the that all work is done */
+		bi->nmsgs = 0;
+		/* wake up our bh */
+		complete(&bi->done);
+	} else if (s & BSC_S_DONE) {
+		bi->nmsgs--;
+
+		if (bi->msg->flags & I2C_M_RD) {
+			bcm2708_bsc_fifo_drain(bi);
+		}
+
+		bcm2708_bsc_reset(bi);
+
+		if (bi->nmsgs) {
+			/* advance to next message */
+			bi->msg++;
+			bi->pos = 0;
+			ret = bcm2708_bsc_setup(bi);
+			if (ret < 0) {
+				bcm2708_bsc_reset(bi);
+				bi->error = true;
+				bi->msg = 0; /* to inform the that all work is done */
+				bi->nmsgs = 0;
+				/* wake up our bh */
+				complete(&bi->done);
+				goto early_exit;
+			}
+		} else {
+			bi->msg = 0; /* to inform the that all work is done */
+			bi->nmsgs = 0;
+			/* wake up our bh */
+			complete(&bi->done);
+		}
+	} else if (s & BSC_S_TXW) {
+		bcm2708_bsc_fifo_fill(bi);
+	} else if (s & BSC_S_RXR) {
+		bcm2708_bsc_fifo_drain(bi);
+	} else {
+		handled = false;
+	}
+
+early_exit:
+	spin_unlock(&bi->lock);
+
+	return handled ? IRQ_HANDLED : IRQ_NONE;
+}
+
+static int bcm2708_i2c_master_xfer(struct i2c_adapter *adap,
+	struct i2c_msg *msgs, int num)
+{
+	struct bcm2708_i2c *bi = adap->algo_data;
+	unsigned long flags;
+	int ret;
+
+	spin_lock_irqsave(&bi->lock, flags);
+
+	reinit_completion(&bi->done);
+	bi->msg = msgs;
+	bi->pos = 0;
+	bi->nmsgs = num;
+	bi->error = false;
+
+	ret = bcm2708_bsc_setup(bi);
+
+	spin_unlock_irqrestore(&bi->lock, flags);
+
+	/* check the result of the setup */
+	if (ret < 0)
+	{
+		dev_err(&adap->dev, "transfer setup timed out\n");
+		goto error_timeout;
+	}
+
+	ret = wait_for_completion_timeout(&bi->done, adap->timeout);
+	if (ret == 0) {
+		dev_err(&adap->dev, "transfer timed out\n");
+		goto error_timeout;
+	}
+
+	ret = bi->error ? -EIO : num;
+	return ret;
+
+error_timeout:
+	spin_lock_irqsave(&bi->lock, flags);
+	bcm2708_bsc_reset(bi);
+	bi->msg = 0; /* to inform the interrupt handler that there's nothing else to be done */
+	bi->nmsgs = 0;
+	spin_unlock_irqrestore(&bi->lock, flags);
+	return -ETIMEDOUT;
+}
+
+static u32 bcm2708_i2c_functionality(struct i2c_adapter *adap)
+{
+	return I2C_FUNC_I2C | /*I2C_FUNC_10BIT_ADDR |*/ I2C_FUNC_SMBUS_EMUL;
+}
+
+static struct i2c_algorithm bcm2708_i2c_algorithm = {
+	.master_xfer = bcm2708_i2c_master_xfer,
+	.functionality = bcm2708_i2c_functionality,
+};
+
+static int bcm2708_i2c_probe(struct platform_device *pdev)
+{
+	struct resource *regs;
+	int irq, err = -ENOMEM;
+	struct clk *clk;
+	struct bcm2708_i2c *bi;
+	struct i2c_adapter *adap;
+	unsigned long bus_hz;
+	u32 cdiv, clk_tout;
+	u32 baud;
+
+	baud = CONFIG_I2C_BCM2708_BAUDRATE;
+
+	if (pdev->dev.of_node) {
+		u32 bus_clk_rate;
+		pdev->id = of_alias_get_id(pdev->dev.of_node, "i2c");
+		if (pdev->id < 0) {
+			dev_err(&pdev->dev, "alias is missing\n");
+			return -EINVAL;
+		}
+		if (!of_property_read_u32(pdev->dev.of_node,
+					"clock-frequency", &bus_clk_rate))
+			baud = bus_clk_rate;
+		else
+			dev_warn(&pdev->dev,
+				"Could not read clock-frequency property\n");
+	}
+
+	if (baudrate)
+		baud = baudrate;
+
+	regs = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	if (!regs) {
+		dev_err(&pdev->dev, "could not get IO memory\n");
+		return -ENXIO;
+	}
+
+	irq = platform_get_irq(pdev, 0);
+	if (irq < 0) {
+		dev_err(&pdev->dev, "could not get IRQ\n");
+		return irq;
+	}
+
+	clk = clk_get(&pdev->dev, NULL);
+	if (IS_ERR(clk)) {
+		dev_err(&pdev->dev, "could not find clk: %ld\n", PTR_ERR(clk));
+		return PTR_ERR(clk);
+	}
+
+	err = clk_prepare_enable(clk);
+	if (err) {
+		dev_err(&pdev->dev, "could not enable clk: %d\n", err);
+		goto out_clk_put;
+	}
+
+	bi = kzalloc(sizeof(*bi), GFP_KERNEL);
+	if (!bi)
+		goto out_clk_disable;
+
+	platform_set_drvdata(pdev, bi);
+
+	adap = &bi->adapter;
+	adap->class = I2C_CLASS_HWMON | I2C_CLASS_DDC;
+	adap->algo = &bcm2708_i2c_algorithm;
+	adap->algo_data = bi;
+	adap->dev.parent = &pdev->dev;
+	adap->nr = pdev->id;
+	strlcpy(adap->name, dev_name(&pdev->dev), sizeof(adap->name));
+	adap->dev.of_node = pdev->dev.of_node;
+
+	switch (pdev->id) {
+	case 0:
+		adap->class = I2C_CLASS_HWMON;
+		break;
+	case 1:
+		adap->class = I2C_CLASS_DDC;
+		break;
+	case 2:
+		adap->class = I2C_CLASS_DDC;
+		break;
+	default:
+		dev_err(&pdev->dev, "can only bind to BSC 0, 1 or 2\n");
+		err = -ENXIO;
+		goto out_free_bi;
+	}
+
+	spin_lock_init(&bi->lock);
+	init_completion(&bi->done);
+
+	bi->base = ioremap(regs->start, resource_size(regs));
+	if (!bi->base) {
+		dev_err(&pdev->dev, "could not remap memory\n");
+		goto out_free_bi;
+	}
+
+	bi->irq = irq;
+	bi->clk = clk;
+
+	err = request_irq(irq, bcm2708_i2c_interrupt, IRQF_SHARED,
+			dev_name(&pdev->dev), bi);
+	if (err) {
+		dev_err(&pdev->dev, "could not request IRQ: %d\n", err);
+		goto out_iounmap;
+	}
+
+	bcm2708_bsc_reset(bi);
+
+	err = i2c_add_numbered_adapter(adap);
+	if (err < 0) {
+		dev_err(&pdev->dev, "could not add I2C adapter: %d\n", err);
+		goto out_free_irq;
+	}
+
+	bus_hz = clk_get_rate(bi->clk);
+	cdiv = bus_hz / baud;
+	if (cdiv > 0xffff) {
+		cdiv = 0xffff;
+		baud = bus_hz / cdiv;
+	}
+
+	clk_tout = 35/1000*baud; //35ms timeout as per SMBus specs.
+	if (clk_tout > 0xffff)
+		clk_tout = 0xffff;
+	
+	bi->cdiv = cdiv;
+	bi->clk_tout = clk_tout;
+
+	dev_info(&pdev->dev, "BSC%d Controller at 0x%08lx (irq %d) (baudrate %d)\n",
+		pdev->id, (unsigned long)regs->start, irq, baud);
+
+	return 0;
+
+out_free_irq:
+	free_irq(bi->irq, bi);
+out_iounmap:
+	iounmap(bi->base);
+out_free_bi:
+	kfree(bi);
+out_clk_disable:
+	clk_disable_unprepare(clk);
+out_clk_put:
+	clk_put(clk);
+	return err;
+}
+
+static int bcm2708_i2c_remove(struct platform_device *pdev)
+{
+	struct bcm2708_i2c *bi = platform_get_drvdata(pdev);
+
+	platform_set_drvdata(pdev, NULL);
+
+	i2c_del_adapter(&bi->adapter);
+	free_irq(bi->irq, bi);
+	iounmap(bi->base);
+	clk_disable_unprepare(bi->clk);
+	clk_put(bi->clk);
+	kfree(bi);
+
+	return 0;
+}
+
+static const struct of_device_id bcm2708_i2c_of_match[] = {
+        { .compatible = "brcm,bcm2708-i2c" },
+        {},
+};
+MODULE_DEVICE_TABLE(of, bcm2708_i2c_of_match);
+
+static struct platform_driver bcm2708_i2c_driver = {
+	.driver		= {
+		.name	= DRV_NAME,
+		.owner	= THIS_MODULE,
+		.of_match_table = bcm2708_i2c_of_match,
+	},
+	.probe		= bcm2708_i2c_probe,
+	.remove		= bcm2708_i2c_remove,
+};
+
+// module_platform_driver(bcm2708_i2c_driver);
+
+
+static int __init bcm2708_i2c_init(void)
+{
+	return platform_driver_register(&bcm2708_i2c_driver);
+}
+
+static void __exit bcm2708_i2c_exit(void)
+{
+	platform_driver_unregister(&bcm2708_i2c_driver);
+}
+
+module_init(bcm2708_i2c_init);
+module_exit(bcm2708_i2c_exit);
+
+
+
+MODULE_DESCRIPTION("BSC controller driver for Broadcom BCM2708");
+MODULE_AUTHOR("Chris Boot <bootc@bootc.net>");
+MODULE_LICENSE("GPL v2");
+MODULE_ALIAS("platform:" DRV_NAME);
