[PATCH v2] i2c: add Atmel AT91 driver
Raphaël Poggi
poggi.raph at gmail.com
Thu Jul 24 05:01:43 PDT 2014
Signed-off-by: Raphaël Poggi <poggi.raph at gmail.com>
---
drivers/i2c/busses/Kconfig | 4 +
drivers/i2c/busses/Makefile | 1 +
drivers/i2c/busses/i2c-at91.c | 437 +++++++++++++++++++++++++++++++++++++++++
3 files changed, 442 insertions(+)
create mode 100644 drivers/i2c/busses/i2c-at91.c
diff --git a/drivers/i2c/busses/Kconfig b/drivers/i2c/busses/Kconfig
index 370abb0..5b75449 100644
--- a/drivers/i2c/busses/Kconfig
+++ b/drivers/i2c/busses/Kconfig
@@ -12,6 +12,10 @@ config I2C_GPIO
This is a very simple bitbanging I2C driver utilizing the
arch-neutral GPIO API to control the SCL and SDA lines.
+config I2C_AT91
+ bool "AT91 I2C Master driver"
+ depends on ARCH_AT91
+
config I2C_IMX
bool "MPC85xx/i.MX I2C Master driver"
depends on (ARCH_IMX && !ARCH_IMX1) || ARCH_MPC85XX
diff --git a/drivers/i2c/busses/Makefile b/drivers/i2c/busses/Makefile
index 9823d1b..cc72b7c 100644
--- a/drivers/i2c/busses/Makefile
+++ b/drivers/i2c/busses/Makefile
@@ -1,3 +1,4 @@
+obj-$(CONFIG_I2C_AT91) += i2c-at91.o
obj-$(CONFIG_I2C_GPIO) += i2c-gpio.o
obj-$(CONFIG_I2C_IMX) += i2c-imx.o
obj-$(CONFIG_I2C_OMAP) += i2c-omap.o
diff --git a/drivers/i2c/busses/i2c-at91.c b/drivers/i2c/busses/i2c-at91.c
new file mode 100644
index 0000000..399f6a9
--- /dev/null
+++ b/drivers/i2c/busses/i2c-at91.c
@@ -0,0 +1,437 @@
+/*
+ * i2c Support for Atmel's AT91 Two-Wire Interface (TWI)
+ *
+ * Copyright (C) 2011 Weinmann Medical GmbH
+ * Author: Nikolaus Voss <n.voss at weinmann.de>
+ *
+ * Evolved from original work by:
+ * Copyright (C) 2004 Rick Bronson
+ * Converted to 2.6 by Andrew Victor <andrew at sanpeople.com>
+ *
+ * Borrowed heavily from original work by:
+ * Copyright (C) 2000 Philip Edelbrock <phil at stimpy.netroedge.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.
+ */
+
+#include <common.h>
+#include <clock.h>
+#include <i2c/i2c.h>
+#include <malloc.h>
+#include <of.h>
+#include <io.h>
+#include <linux/clk.h>
+#include <linux/err.h>
+#include <driver.h>
+#include <init.h>
+
+#define DEFAULT_TWI_CLK_HZ 100000 /* max 400 Kbits/s */
+#define AT91_I2C_TIMEOUT (100 * MSECOND) /* transfer timeout */
+#define AT91_I2C_DMA_THRESHOLD 8 /* enable DMA if transfer size is bigger than this threshold */
+
+/* AT91 TWI register definitions */
+#define AT91_TWI_CR 0x0000 /* Control Register */
+#define AT91_TWI_START 0x0001 /* Send a Start Condition */
+#define AT91_TWI_STOP 0x0002 /* Send a Stop Condition */
+#define AT91_TWI_MSEN 0x0004 /* Master Transfer Enable */
+#define AT91_TWI_SVDIS 0x0020 /* Slave Transfer Disable */
+#define AT91_TWI_QUICK 0x0040 /* SMBus quick command */
+#define AT91_TWI_SWRST 0x0080 /* Software Reset */
+
+#define AT91_TWI_MMR 0x0004 /* Master Mode Register */
+#define AT91_TWI_IADRSZ_1 0x0100 /* Internal Device Address Size */
+#define AT91_TWI_MREAD 0x1000 /* Master Read Direction */
+
+#define AT91_TWI_IADR 0x000c /* Internal Address Register */
+
+#define AT91_TWI_CWGR 0x0010 /* Clock Waveform Generator Reg */
+
+#define AT91_TWI_SR 0x0020 /* Status Register */
+#define AT91_TWI_TXCOMP 0x0001 /* Transmission Complete */
+#define AT91_TWI_RXRDY 0x0002 /* Receive Holding Register Ready */
+#define AT91_TWI_TXRDY 0x0004 /* Transmit Holding Register Ready */
+
+#define AT91_TWI_OVRE 0x0040 /* Overrun Error */
+#define AT91_TWI_UNRE 0x0080 /* Underrun Error */
+#define AT91_TWI_NACK 0x0100 /* Not Acknowledged */
+
+#define AT91_TWI_IER 0x0024 /* Interrupt Enable Register */
+#define AT91_TWI_IDR 0x0028 /* Interrupt Disable Register */
+#define AT91_TWI_IMR 0x002c /* Interrupt Mask Register */
+#define AT91_TWI_RHR 0x0030 /* Receive Holding Register */
+#define AT91_TWI_THR 0x0034 /* Transmit Holding Register */
+
+struct at91_twi_pdata {
+ unsigned clk_max_div;
+ unsigned clk_offset;
+ bool has_unre_flag;
+};
+
+struct at91_twi_dev {
+ struct device *dev;
+ void __iomem *base;
+ struct clk *clk;
+ u8 *buf;
+ size_t buf_len;
+ struct i2c_msg *msg;
+ unsigned imr;
+ unsigned transfer_status;
+ struct i2c_adapter adapter;
+ unsigned twi_cwgr_reg;
+ struct at91_twi_pdata *pdata;
+};
+
+#define to_at91_twi_dev(a) container_of(a, struct at91_twi_dev, adapter)
+
+static unsigned at91_twi_read(struct at91_twi_dev *dev, unsigned reg)
+{
+ return __raw_readl(dev->base + reg);
+}
+
+static void at91_twi_write(struct at91_twi_dev *dev, unsigned reg, unsigned val)
+{
+ __raw_writel(val, dev->base + reg);
+}
+
+static void at91_disable_twi_interrupts(struct at91_twi_dev *dev)
+{
+ at91_twi_write(dev, AT91_TWI_IDR,
+ AT91_TWI_TXCOMP | AT91_TWI_RXRDY | AT91_TWI_TXRDY);
+}
+
+static void at91_init_twi_bus(struct at91_twi_dev *dev)
+{
+ at91_disable_twi_interrupts(dev);
+ at91_twi_write(dev, AT91_TWI_CR, AT91_TWI_SWRST);
+ at91_twi_write(dev, AT91_TWI_CR, AT91_TWI_MSEN);
+ at91_twi_write(dev, AT91_TWI_CR, AT91_TWI_SVDIS);
+ at91_twi_write(dev, AT91_TWI_CWGR, dev->twi_cwgr_reg);
+}
+
+/*
+ * Calculate symmetric clock as stated in datasheet:
+ * twi_clk = F_MAIN / (2 * (cdiv * (1 << ckdiv) + offset))
+ */
+static void at91_calc_twi_clock(struct at91_twi_dev *dev, int twi_clk)
+{
+ int ckdiv, cdiv, div;
+ struct at91_twi_pdata *pdata = dev->pdata;
+ int offset = pdata->clk_offset;
+ int max_ckdiv = pdata->clk_max_div;
+
+ div = max(0, (int)DIV_ROUND_UP(clk_get_rate(dev->clk),
+ 2 * twi_clk) - offset);
+ ckdiv = fls(div >> 8);
+ cdiv = div >> ckdiv;
+
+ if (ckdiv > max_ckdiv) {
+ dev_warn(&dev->adapter.dev, "%d exceeds ckdiv max value which is %d.\n",
+ ckdiv, max_ckdiv);
+ ckdiv = max_ckdiv;
+ cdiv = 255;
+ }
+
+ dev->twi_cwgr_reg = (ckdiv << 16) | (cdiv << 8) | cdiv;
+ dev_dbg(&dev->adapter.dev, "cdiv %d ckdiv %d\n", cdiv, ckdiv);
+}
+
+static void at91_twi_write_next_byte(struct at91_twi_dev *dev)
+{
+ if (dev->buf_len <= 0)
+ return;
+
+ at91_twi_write(dev, AT91_TWI_THR, *dev->buf);
+
+ /* send stop when last byte has been written */
+ if (--dev->buf_len == 0)
+ at91_twi_write(dev, AT91_TWI_CR, AT91_TWI_STOP);
+
+ dev_dbg(&dev->adapter.dev, "wrote 0x%x, to go %d\n", *dev->buf, dev->buf_len);
+
+ ++dev->buf;
+}
+
+static void at91_twi_read_next_byte(struct at91_twi_dev *dev)
+{
+ if (dev->buf_len <= 0)
+ return;
+
+ *dev->buf = at91_twi_read(dev, AT91_TWI_RHR) & 0xff;
+ --dev->buf_len;
+
+ /* send stop if second but last byte has been read */
+ if (dev->buf_len == 1)
+ at91_twi_write(dev, AT91_TWI_CR, AT91_TWI_STOP);
+
+ dev_dbg(&dev->adapter.dev, "read 0x%x, to go %d\n", *dev->buf, dev->buf_len);
+
+ ++dev->buf;
+}
+
+static int at91_twi_wait_completion(struct at91_twi_dev *dev)
+{
+ uint64_t start = get_time_ns();
+ unsigned int status = at91_twi_read(dev, AT91_TWI_SR);
+ unsigned int irqstatus = at91_twi_read(dev, AT91_TWI_IMR);
+
+ if (irqstatus & AT91_TWI_RXRDY)
+ at91_twi_read_next_byte(dev);
+ else if (irqstatus & AT91_TWI_TXRDY)
+ at91_twi_write_next_byte(dev);
+ else
+ dev_warn(&dev->adapter.dev, "neither rx and tx are ready\n");
+
+ dev->transfer_status |= status;
+
+ while(!(at91_twi_read(dev, AT91_TWI_SR) & AT91_TWI_TXCOMP)) {
+ if(is_timeout(start, AT91_I2C_TIMEOUT)) {
+ dev_warn(&dev->adapter.dev, "timeout waiting for bus ready\n");
+ return -ETIMEDOUT;
+ }
+ }
+
+ at91_disable_twi_interrupts(dev);
+
+ return 0;
+}
+
+static int at91_do_twi_transfer(struct at91_twi_dev *dev)
+{
+ int ret;
+ bool has_unre_flag = dev->pdata->has_unre_flag;
+
+ dev_dbg(&dev->adapter.dev, "transfer: %s %d bytes.\n",
+ (dev->msg->flags & I2C_M_RD) ? "read" : "write", dev->buf_len);
+
+ dev->transfer_status = 0;
+
+ if (!dev->buf_len) {
+ at91_twi_write(dev, AT91_TWI_CR, AT91_TWI_QUICK);
+ at91_twi_write(dev, AT91_TWI_IER, AT91_TWI_TXCOMP);
+ } else if (dev->msg->flags & I2C_M_RD) {
+ unsigned start_flags = AT91_TWI_START;
+
+ if (at91_twi_read(dev, AT91_TWI_SR) & AT91_TWI_RXRDY) {
+ dev_err(&dev->adapter.dev, "RXRDY still set!");
+ at91_twi_read(dev, AT91_TWI_RHR);
+ }
+
+ /* if only one byte is to be read, immediately stop transfer */
+ if (dev->buf_len <= 1)
+ start_flags |= AT91_TWI_STOP;
+
+ at91_twi_write(dev, AT91_TWI_CR, start_flags);
+
+ at91_twi_write(dev, AT91_TWI_IER,
+ AT91_TWI_TXCOMP | AT91_TWI_RXRDY);
+ } else {
+ at91_twi_write_next_byte(dev);
+ at91_twi_write(dev, AT91_TWI_IER,
+ AT91_TWI_TXCOMP | AT91_TWI_TXRDY);
+ }
+
+ ret = at91_twi_wait_completion(dev);
+ if (ret < 0) {
+ dev_err(&dev->adapter.dev, "controller timed out\n");
+ at91_init_twi_bus(dev);
+ ret = -ETIMEDOUT;
+ goto error;
+ }
+ if (dev->transfer_status & AT91_TWI_NACK) {
+ dev_dbg(&dev->adapter.dev, "received nack\n");
+ ret = -EREMOTEIO;
+ goto error;
+ }
+ if (dev->transfer_status & AT91_TWI_OVRE) {
+ dev_err(&dev->adapter.dev, "overrun while reading\n");
+ ret = -EIO;
+ goto error;
+ }
+ if (has_unre_flag && dev->transfer_status & AT91_TWI_UNRE) {
+ dev_err(&dev->adapter.dev, "underrun while writing\n");
+ ret = -EIO;
+ goto error;
+ }
+ dev_dbg(&dev->adapter.dev, "transfer complete\n");
+
+ return 0;
+
+error:
+ return ret;
+}
+
+static int at91_twi_xfer(struct i2c_adapter *adap, struct i2c_msg *msg, int num)
+{
+ struct at91_twi_dev *dev = to_at91_twi_dev(adap);
+ int ret;
+ unsigned int_addr_flag = 0;
+ struct i2c_msg *m_start = msg;
+
+ dev_dbg(&adap->dev, "at91_xfer: processing %d messages:\n", num);
+
+ /*
+ * The hardware can handle at most two messages concatenated by a
+ * repeated start via it's internal address feature.
+ */
+ if (num > 2) {
+ dev_err(&dev->adapter.dev,
+ "cannot handle more than two concatenated messages.\n");
+ return 0;
+ } else if (num == 2) {
+ int internal_address = 0;
+ int i;
+
+ if (msg->flags & I2C_M_RD) {
+ dev_err(&dev->adapter.dev, "first transfer must be write.\n");
+ return -EINVAL;
+ }
+ if (msg->len > 3) {
+ dev_err(&dev->adapter.dev, "first message size must be <= 3.\n");
+ return -EINVAL;
+ }
+
+ /* 1st msg is put into the internal address, start with 2nd */
+ m_start = &msg[1];
+ for (i = 0; i < msg->len; ++i) {
+ const unsigned addr = msg->buf[msg->len - 1 - i];
+
+ internal_address |= addr << (8 * i);
+ int_addr_flag += AT91_TWI_IADRSZ_1;
+ }
+ at91_twi_write(dev, AT91_TWI_IADR, internal_address);
+ }
+
+ at91_twi_write(dev, AT91_TWI_MMR, (m_start->addr << 16) | int_addr_flag
+ | ((m_start->flags & I2C_M_RD) ? AT91_TWI_MREAD : 0));
+
+ dev->buf_len = m_start->len;
+ dev->buf = m_start->buf;
+ dev->msg = m_start;
+
+ ret = at91_do_twi_transfer(dev);
+
+ return (ret < 0) ? ret : num;
+}
+
+static struct at91_twi_pdata at91rm9200_config = {
+ .clk_max_div = 5,
+ .clk_offset = 3,
+ .has_unre_flag = true,
+};
+
+static struct at91_twi_pdata at91sam9261_config = {
+ .clk_max_div = 5,
+ .clk_offset = 4,
+ .has_unre_flag = false,
+};
+
+static struct at91_twi_pdata at91sam9260_config = {
+ .clk_max_div = 7,
+ .clk_offset = 4,
+ .has_unre_flag = false,
+};
+
+static struct at91_twi_pdata at91sam9g20_config = {
+ .clk_max_div = 7,
+ .clk_offset = 4,
+ .has_unre_flag = false,
+};
+
+static struct at91_twi_pdata at91sam9g10_config = {
+ .clk_max_div = 7,
+ .clk_offset = 4,
+ .has_unre_flag = false,
+};
+
+static struct platform_device_id at91_twi_devtypes[] = {
+ {
+ .name = "i2c-at91rm9200",
+ .driver_data = (unsigned long) &at91rm9200_config,
+ }, {
+ .name = "i2c-at91sam9261",
+ .driver_data = (unsigned long) &at91sam9261_config,
+ }, {
+ .name = "i2c-at91sam9260",
+ .driver_data = (unsigned long) &at91sam9260_config,
+ }, {
+ .name = "i2c-at91sam9g20",
+ .driver_data = (unsigned long) &at91sam9g20_config,
+ }, {
+ .name = "i2c-at91sam9g10",
+ .driver_data = (unsigned long) &at91sam9g10_config,
+ }, {
+ /* sentinel */
+ }
+};
+
+static int at91_twi_probe(struct device_d *dev)
+{
+ struct at91_twi_dev *i2c_at91;
+ struct at91_twi_pdata *i2c_data;
+ int rc;
+ u32 bus_clk_rate;
+
+ i2c_at91 = xzalloc(sizeof(struct at91_twi_dev));
+
+ rc = dev_get_drvdata(dev, (unsigned long *)&i2c_data);
+ if (rc)
+ goto out_free;
+
+ i2c_at91->pdata = i2c_data;
+
+ i2c_at91->base = dev_request_mem_region(dev, 0);
+ if (!i2c_at91->base) {
+ dev_err(dev, "could not get memory region\n");
+ rc = -ENODEV;
+ goto out_free;
+ }
+
+ i2c_at91->clk = clk_get(dev, "twi_clk");
+ if (IS_ERR(i2c_at91->clk)) {
+ dev_err(dev, "no clock defined\n");
+ rc = -ENODEV;
+ goto out_free;
+ }
+
+ clk_enable(i2c_at91->clk);
+
+ bus_clk_rate = DEFAULT_TWI_CLK_HZ;
+
+ at91_calc_twi_clock(i2c_at91, bus_clk_rate);
+ at91_init_twi_bus(i2c_at91);
+
+ i2c_at91->adapter.master_xfer = at91_twi_xfer;
+ i2c_at91->adapter.dev.parent = dev;
+ i2c_at91->adapter.nr = dev->id;
+ i2c_at91->adapter.dev.device_node = dev->device_node;
+
+ rc = i2c_add_numbered_adapter(&i2c_at91->adapter);
+ if (rc) {
+ dev_err(dev, "Failed to add I2C adapter\n");
+ goto out_adap_fail;
+ }
+
+ dev_info(dev, "AT91 i2c bus driver.\n");
+ return 0;
+
+out_adap_fail:
+ clk_disable(i2c_at91->clk);
+ clk_put(i2c_at91->clk);
+out_free:
+ kfree(i2c_at91);
+ return rc;
+}
+
+static struct driver_d at91_twi_driver = {
+ .name = "at91-twi",
+ .probe = at91_twi_probe,
+ .id_table = at91_twi_devtypes,
+};
+device_platform_driver(at91_twi_driver);
+
+MODULE_AUTHOR("Nikolaus Voss <n.voss at weinmann.de>");
+MODULE_DESCRIPTION("I2C (TWI) driver for Atmel AT91");
+MODULE_LICENSE("GPL");
--
1.7.9.5
More information about the barebox
mailing list