i2c: Add support for the Arm's Versatile Express I2C controller.

The Arm Versatile Express I2C controller is a simple register-based
controller that uses a register to control the state of the SCL and
SDA lines. Add support for it.

Signed-off-by: Liviu Dudau <liviu.dudau@foss.arm.com>
Reviewed-by: Heiko Schocher <hs@denx.de>

diff --git a/drivers/i2c/i2c-versatile.c b/drivers/i2c/i2c-versatile.c
new file mode 100644 (file)
index 0000000..f523844
--- /dev/null
+++ b/drivers/i2c/i2c-versatile.c
@@ -0,0 +1,280 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (c) 2018 Arm Ltd.
+ * Author: Liviu Dudau <liviu.dudau@foss.arm.com>
+ *
+ */
+
+#include <common.h>
+#include <dm.h>
+#include <errno.h>
+#include <i2c.h>
+#include <asm/io.h>
+#include <clk.h>
+#include <linux/io.h>
+
+#define I2C_CONTROL_REG                0x00
+#define I2C_SET_REG            0x00
+#define I2C_CLEAR_REG          0x04
+
+#define SCL    BIT(0)
+#define SDA    BIT(1)
+
+struct versatile_i2c_priv {
+       phys_addr_t base;
+       u32 delay;
+};
+
+static inline void versatile_sda_set(struct versatile_i2c_priv *priv, u8 state)
+{
+       writel(SDA, priv->base + (state ? I2C_SET_REG : I2C_CLEAR_REG));
+       udelay(priv->delay);
+}
+
+static inline int versatile_sda_get(struct versatile_i2c_priv *priv)
+{
+       int v = !!(readl(priv->base + I2C_CONTROL_REG) & SDA);
+
+       udelay(priv->delay);
+       return v;
+}
+
+static inline void versatile_scl_set(struct versatile_i2c_priv *priv, u8 state)
+{
+       writel(SCL, priv->base + (state ? I2C_SET_REG : I2C_CLEAR_REG));
+       udelay(priv->delay);
+}
+
+static inline int versatile_scl_get(struct versatile_i2c_priv *priv)
+{
+       int v = !!(readl(priv->base + I2C_CONTROL_REG) & SCL);
+
+       udelay(priv->delay);
+       return v;
+}
+
+/* start: SDA goes from high to low while SCL is high */
+static void versatile_i2c_start(struct versatile_i2c_priv *priv)
+{
+       udelay(priv->delay);
+       versatile_sda_set(priv, 1);
+       versatile_scl_set(priv, 1);
+       versatile_sda_set(priv, 0);
+}
+
+/* stop: SDA goes from low to high while SCL is high */
+static void versatile_i2c_stop(struct versatile_i2c_priv *priv)
+{
+       versatile_scl_set(priv, 0);
+       versatile_sda_set(priv, 0);
+       versatile_scl_set(priv, 1);
+       versatile_sda_set(priv, 1);
+}
+
+/* read a bit from the SDA line (data or ACK/NACK) */
+static u8 versatile_i2c_read_bit(struct versatile_i2c_priv *priv)
+{
+       versatile_scl_set(priv, 0);
+       versatile_sda_set(priv, 1);
+       versatile_scl_set(priv, 1);
+       udelay(priv->delay);
+       return (u8)versatile_sda_get(priv);
+}
+
+/* write a bit on the SDA line */
+static void versatile_i2c_write_bit(struct versatile_i2c_priv *priv, u8 bit)
+{
+       versatile_scl_set(priv, 0);
+       versatile_sda_set(priv, bit);
+       versatile_scl_set(priv, 1);
+       udelay(priv->delay);
+}
+
+/* send a reset sequence of 9 clocks with SDA high */
+static void versatile_i2c_reset_bus(struct versatile_i2c_priv *priv)
+{
+       int i;
+
+       for (i = 0; i < 9; i++)
+               versatile_i2c_write_bit(priv, 1);
+
+       versatile_i2c_stop(priv);
+}
+
+/* write byte without start/stop sequence */
+static int versatile_i2c_write_byte(struct versatile_i2c_priv *priv, u8 byte)
+{
+       u8 nak, i;
+
+       for (i = 0; i < 8; i++) {
+               versatile_i2c_write_bit(priv, byte & 0x80);
+               byte <<= 1;
+       }
+
+       /* read ACK */
+       nak = versatile_i2c_read_bit(priv);
+       versatile_scl_set(priv, 0);
+
+       return nak;     /* not a nack is an ack */
+}
+
+static int versatile_i2c_read_byte(struct versatile_i2c_priv *priv,
+                                  u8 *byte, u8 ack)
+{
+       u8 i;
+
+       *byte = 0;
+       for (i = 0; i < 8; i++) {
+               *byte <<= 1;
+               *byte |= versatile_i2c_read_bit(priv);
+       }
+       /* write the nack */
+       versatile_i2c_write_bit(priv, ack);
+
+       return 0;
+}
+
+static int versatile_i2c_send_slave_addr(struct versatile_i2c_priv *priv,
+                                        struct i2c_msg *msg)
+{
+       u8 addr;
+       int ret;
+
+       if (msg->flags & I2C_M_TEN) {
+               /* 10-bit address, send extended address code first */
+               addr = 0xf0 | ((msg->addr >> 7) & 0x06);
+               ret = versatile_i2c_write_byte(priv, addr);
+               if (ret) {
+                       versatile_i2c_stop(priv);
+                       return -EIO;
+               }
+
+               /* remaining bits */
+               ret = versatile_i2c_write_byte(priv, msg->addr & 0xff);
+               if (ret) {
+                       versatile_i2c_stop(priv);
+                       return -EIO;
+               }
+               /* reads need to resend the addr */
+               if (msg->flags & I2C_M_RD) {
+                       versatile_i2c_start(priv);
+                       addr |= 1;
+                       ret = versatile_i2c_write_byte(priv, addr);
+                       if (ret) {
+                               versatile_i2c_stop(priv);
+                               return -EIO;
+                       }
+               }
+       } else {
+               /* normal 7-bit address */
+               addr = msg->addr << 1;
+               if (msg->flags & I2C_M_RD)
+                       addr |= 1;
+               ret = versatile_i2c_write_byte(priv, addr);
+               if (ret) {
+                       versatile_i2c_stop(priv);
+                       return -EIO;
+               }
+       }
+
+       return 0;
+}
+
+static int versatile_i2c_message_xfer(struct versatile_i2c_priv *priv,
+                                     struct i2c_msg *msg)
+{
+       int i, ret;
+       u8 ack;
+
+       versatile_i2c_start(priv);
+       if (versatile_i2c_send_slave_addr(priv, msg))
+               return -EIO;
+
+       for (i = 0; i < msg->len; i++) {
+               if (msg->flags & I2C_M_RD) {
+                       ack = (msg->len - i - 1) == 0 ? 1 : 0;
+                       ret = versatile_i2c_read_byte(priv, &msg->buf[i], ack);
+               } else {
+                       ret = versatile_i2c_write_byte(priv, msg->buf[i]);
+               }
+
+               if (ret)
+                       break;
+       }
+
+       versatile_i2c_stop(priv);
+
+       return ret;
+}
+
+static int versatile_i2c_xfer(struct udevice *bus,
+                             struct i2c_msg *msg, int nmsgs)
+{
+       struct versatile_i2c_priv *priv = dev_get_priv(bus);
+       int ret;
+
+       for ( ; nmsgs > 0; nmsgs--, msg++) {
+               ret = versatile_i2c_message_xfer(priv, msg);
+               if (ret)
+                       return -EREMOTEIO;
+       }
+
+       return 0;
+}
+
+static int versatile_i2c_chip_probe(struct udevice *bus,
+                                   uint chip, uint chip_flags)
+{
+       /* probe the presence of a slave by writing a 0-size message */
+       struct i2c_msg msg = { .addr = chip, .flags = chip_flags,
+                              .len = 0, .buf = NULL };
+       struct versatile_i2c_priv *priv = dev_get_priv(bus);
+
+       return versatile_i2c_message_xfer(priv, &msg);
+}
+
+static int versatile_i2c_set_bus_speed(struct udevice *bus, unsigned int speed)
+{
+       struct versatile_i2c_priv *priv = dev_get_priv(bus);
+
+       priv->delay = 1000000 / (speed << 2);
+
+       versatile_i2c_reset_bus(priv);
+
+       return 0;
+}
+
+static int versatile_i2c_probe(struct udevice *dev)
+{
+       struct versatile_i2c_priv *priv = dev_get_priv(dev);
+
+       priv->base = (phys_addr_t)dev_read_addr(dev);
+       priv->delay = 25;       /* 25us * 4 = 100kHz */
+       /*
+        * U-Boot still doesn't assign automatically
+        * sequence numbers to devices
+        */
+       dev->req_seq = 1;
+
+       return 0;
+}
+
+static const struct dm_i2c_ops versatile_i2c_ops = {
+       .xfer = versatile_i2c_xfer,
+       .probe_chip = versatile_i2c_chip_probe,
+       .set_bus_speed = versatile_i2c_set_bus_speed,
+};
+
+static const struct udevice_id versatile_i2c_of_match[] = {
+       { .compatible = "arm,versatile-i2c" },
+       { }
+};
+
+U_BOOT_DRIVER(versatile_i2c) = {
+       .name = "i2c-bus-versatile",
+       .id = UCLASS_I2C,
+       .of_match = versatile_i2c_of_match,
+       .probe = versatile_i2c_probe,
+       .priv_auto_alloc_size = sizeof(struct versatile_i2c_priv),
+       .ops = &versatile_i2c_ops,
+};