i2c: xiic: Add Xilinx AXI I2C driver

Add Xilinx AXI I2C controller driver based on the Linux i2c-xiic driver.
This driver is stripped of all the IRQ handling and uses pure polling,
yet tries to retain most of the structure of the Linux driver to make
backporting of fixes easy.

Note that the IP has a known limitation on 255 bytes read and write,
according to xilinx this is still being worked on [1].

[1] https://forums.xilinx.com/t5/Embedded-Processor-System-Design/AXI-IIC-V2-0-I2C-Master-Reading-multiple-bytes-from-I2C-slave/m-p/854419/highlight/true#M39387

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Michal Simek <monstr@monstr.eu>
Cc: Michal Simek <michal.simek@xilinx.com>
Cc: Heiko Schocher <hs@denx.de>
Reviewed-by: Heiko Schocher <hs@denx.de>

3 files changed, 347 insertions, 0 deletions

diff --git a/drivers/i2c/Kconfig b/drivers/i2c/Kconfig
index 1ef22e6bcd..536617115a 100644
--- a/drivers/i2c/Kconfig
+++ b/drivers/i2c/Kconfig
@@ -450,6 +450,12 @@ config SYS_I2C_BUS_MAX
 	help
 	  Define the maximum number of available I2C buses.
 
+config SYS_I2C_XILINX_XIIC
+	bool "Xilinx AXI I2C driver"
+	depends on DM_I2C
+	help
+	  Support for Xilinx AXI I2C controller.
+
 config SYS_I2C_ZYNQ
 	bool "Xilinx I2C driver"
 	depends on ARCH_ZYNQMP || ARCH_ZYNQ
diff --git a/drivers/i2c/Makefile b/drivers/i2c/Makefile
index d3637bcd8d..ec2d1964c3 100644
--- a/drivers/i2c/Makefile
+++ b/drivers/i2c/Makefile
@@ -37,6 +37,7 @@ obj-$(CONFIG_SYS_I2C_TEGRA) += tegra_i2c.o
 obj-$(CONFIG_SYS_I2C_UNIPHIER) += i2c-uniphier.o
 obj-$(CONFIG_SYS_I2C_UNIPHIER_F) += i2c-uniphier-f.o
 obj-$(CONFIG_SYS_I2C_VERSATILE) += i2c-versatile.o
+obj-$(CONFIG_SYS_I2C_XILINX_XIIC) += xilinx_xiic.o
 obj-$(CONFIG_SYS_I2C_ZYNQ) += zynq_i2c.o
 obj-$(CONFIG_TEGRA186_BPMP_I2C) += tegra186_bpmp_i2c.o
 
diff --git a/drivers/i2c/xilinx_xiic.c b/drivers/i2c/xilinx_xiic.c
new file mode 100644
index 0000000000..83114ed510
--- /dev/null
+++ b/drivers/i2c/xilinx_xiic.c
@@ -0,0 +1,340 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Xilinx AXI I2C driver
+ *
+ * Copyright (C) 2018 Marek Vasut <marex@denx.de>
+ *
+ * Based on Linux 4.14.y i2c-xiic.c
+ * Copyright (c) 2002-2007 Xilinx Inc.
+ * Copyright (c) 2009-2010 Intel Corporation
+ */
+
+#include <common.h>
+#include <clk.h>
+#include <dm.h>
+#include <i2c.h>
+#include <wait_bit.h>
+#include <asm/io.h>
+
+struct xilinx_xiic_priv {
+	void __iomem		*base;
+	struct clk		clk;
+};
+
+#define XIIC_MSB_OFFSET 0
+#define XIIC_REG_OFFSET (0x100+XIIC_MSB_OFFSET)
+
+/*
+ * Register offsets in bytes from RegisterBase. Three is added to the
+ * base offset to access LSB (IBM style) of the word
+ */
+#define XIIC_CR_REG_OFFSET   (0x00+XIIC_REG_OFFSET)	/* Control Register   */
+#define XIIC_SR_REG_OFFSET   (0x04+XIIC_REG_OFFSET)	/* Status Register    */
+#define XIIC_DTR_REG_OFFSET  (0x08+XIIC_REG_OFFSET)	/* Data Tx Register   */
+#define XIIC_DRR_REG_OFFSET  (0x0C+XIIC_REG_OFFSET)	/* Data Rx Register   */
+#define XIIC_ADR_REG_OFFSET  (0x10+XIIC_REG_OFFSET)	/* Address Register   */
+#define XIIC_TFO_REG_OFFSET  (0x14+XIIC_REG_OFFSET)	/* Tx FIFO Occupancy  */
+#define XIIC_RFO_REG_OFFSET  (0x18+XIIC_REG_OFFSET)	/* Rx FIFO Occupancy  */
+#define XIIC_TBA_REG_OFFSET  (0x1C+XIIC_REG_OFFSET)	/* 10 Bit Address reg */
+#define XIIC_RFD_REG_OFFSET  (0x20+XIIC_REG_OFFSET)	/* Rx FIFO Depth reg  */
+#define XIIC_GPO_REG_OFFSET  (0x24+XIIC_REG_OFFSET)	/* Output Register    */
+
+/* Control Register masks */
+#define XIIC_CR_ENABLE_DEVICE_MASK        0x01	/* Device enable = 1      */
+#define XIIC_CR_TX_FIFO_RESET_MASK        0x02	/* Transmit FIFO reset=1  */
+#define XIIC_CR_MSMS_MASK                 0x04	/* Master starts Txing=1  */
+#define XIIC_CR_DIR_IS_TX_MASK            0x08	/* Dir of tx. Txing=1     */
+#define XIIC_CR_NO_ACK_MASK               0x10	/* Tx Ack. NO ack = 1     */
+#define XIIC_CR_REPEATED_START_MASK       0x20	/* Repeated start = 1     */
+#define XIIC_CR_GENERAL_CALL_MASK         0x40	/* Gen Call enabled = 1   */
+
+/* Status Register masks */
+#define XIIC_SR_GEN_CALL_MASK             0x01	/* 1=a mstr issued a GC   */
+#define XIIC_SR_ADDR_AS_SLAVE_MASK        0x02	/* 1=when addr as slave   */
+#define XIIC_SR_BUS_BUSY_MASK             0x04	/* 1 = bus is busy        */
+#define XIIC_SR_MSTR_RDING_SLAVE_MASK     0x08	/* 1=Dir: mstr <-- slave  */
+#define XIIC_SR_TX_FIFO_FULL_MASK         0x10	/* 1 = Tx FIFO full       */
+#define XIIC_SR_RX_FIFO_FULL_MASK         0x20	/* 1 = Rx FIFO full       */
+#define XIIC_SR_RX_FIFO_EMPTY_MASK        0x40	/* 1 = Rx FIFO empty      */
+#define XIIC_SR_TX_FIFO_EMPTY_MASK        0x80	/* 1 = Tx FIFO empty      */
+
+/* Interrupt Status Register masks    Interrupt occurs when...       */
+#define XIIC_INTR_ARB_LOST_MASK           0x01	/* 1 = arbitration lost   */
+#define XIIC_INTR_TX_ERROR_MASK           0x02	/* 1=Tx error/msg complete */
+#define XIIC_INTR_TX_EMPTY_MASK           0x04	/* 1 = Tx FIFO/reg empty  */
+#define XIIC_INTR_RX_FULL_MASK            0x08	/* 1=Rx FIFO/reg=OCY level */
+#define XIIC_INTR_BNB_MASK                0x10	/* 1 = Bus not busy       */
+#define XIIC_INTR_AAS_MASK                0x20	/* 1 = when addr as slave */
+#define XIIC_INTR_NAAS_MASK               0x40	/* 1 = not addr as slave  */
+#define XIIC_INTR_TX_HALF_MASK            0x80	/* 1 = TX FIFO half empty */
+
+/* The following constants specify the depth of the FIFOs */
+#define IIC_RX_FIFO_DEPTH         16	/* Rx fifo capacity               */
+#define IIC_TX_FIFO_DEPTH         16	/* Tx fifo capacity               */
+
+/*
+ * Tx Fifo upper bit masks.
+ */
+#define XIIC_TX_DYN_START_MASK            0x0100 /* 1 = Set dynamic start */
+#define XIIC_TX_DYN_STOP_MASK             0x0200 /* 1 = Set dynamic stop */
+
+/*
+ * The following constants define the register offsets for the Interrupt
+ * registers. There are some holes in the memory map for reserved addresses
+ * to allow other registers to be added and still match the memory map of the
+ * interrupt controller registers
+ */
+#define XIIC_DGIER_OFFSET    0x1C /* Device Global Interrupt Enable Register */
+#define XIIC_IISR_OFFSET     0x20 /* Interrupt Status Register */
+#define XIIC_IIER_OFFSET     0x28 /* Interrupt Enable Register */
+#define XIIC_RESETR_OFFSET   0x40 /* Reset Register */
+
+#define XIIC_RESET_MASK             0xAUL
+
+static u8 i2c_8bit_addr_from_flags(uint addr, u16 flags)
+{
+	return (addr << 1) | (flags & I2C_M_RD ? 1 : 0);
+}
+
+static void xiic_irq_clr(struct xilinx_xiic_priv *priv, u32 mask)
+{
+	u32 isr = readl(priv->base + XIIC_IISR_OFFSET);
+
+	writel(isr & mask, priv->base + XIIC_IISR_OFFSET);
+}
+
+static int xiic_read_rx(struct xilinx_xiic_priv *priv,
+			struct i2c_msg *msg, int nmsgs)
+{
+	u8 bytes_in_fifo;
+	u32 pos = 0;
+	int i, ret;
+
+	while (pos < msg->len) {
+		ret = wait_for_bit_8(priv->base + XIIC_SR_REG_OFFSET,
+				     XIIC_SR_RX_FIFO_EMPTY_MASK, false,
+				     1000, true);
+		if (ret)
+			return ret;
+
+		bytes_in_fifo = readb(priv->base + XIIC_RFO_REG_OFFSET) + 1;
+
+		if (bytes_in_fifo > msg->len)
+			bytes_in_fifo = msg->len;
+
+		for (i = 0; i < bytes_in_fifo; i++) {
+			msg->buf[pos++] = readb(priv->base +
+						XIIC_DRR_REG_OFFSET);
+		}
+	}
+
+	return 0;
+}
+
+static int xiic_tx_fifo_space(struct xilinx_xiic_priv *priv)
+{
+	/* return the actual space left in the FIFO */
+	return IIC_TX_FIFO_DEPTH - readb(priv->base + XIIC_TFO_REG_OFFSET) - 1;
+}
+
+static void xiic_fill_tx_fifo(struct xilinx_xiic_priv *priv,
+			      struct i2c_msg *msg, int nmsgs)
+{
+	u8 fifo_space = xiic_tx_fifo_space(priv);
+	int len = msg->len;
+	u32 pos = 0;
+
+	len = (len > fifo_space) ? fifo_space : len;
+
+	while (len--) {
+		u16 data = msg->buf[pos++];
+
+		if (pos == len && nmsgs == 1) {
+			/* last message in transfer -> STOP */
+			data |= XIIC_TX_DYN_STOP_MASK;
+		}
+		writew(data, priv->base + XIIC_DTR_REG_OFFSET);
+	}
+}
+
+static void xilinx_xiic_set_addr(struct udevice *dev, u8 addr,
+				 u16 flags, u32 len, u32 nmsgs)
+{
+	struct xilinx_xiic_priv *priv = dev_get_priv(dev);
+
+	xiic_irq_clr(priv, XIIC_INTR_TX_ERROR_MASK);
+
+	if (!(flags & I2C_M_NOSTART)) {
+		/* write the address */
+		u16 data = i2c_8bit_addr_from_flags(addr, flags) |
+			XIIC_TX_DYN_START_MASK;
+		if (nmsgs == 1 && len == 0)
+			/* no data and last message -> add STOP */
+			data |= XIIC_TX_DYN_STOP_MASK;
+
+		writew(data, priv->base + XIIC_DTR_REG_OFFSET);
+	}
+}
+
+static int xilinx_xiic_read_common(struct udevice *dev, struct i2c_msg *msg,
+				   u32 nmsgs)
+{
+	struct xilinx_xiic_priv *priv = dev_get_priv(dev);
+	u8 rx_watermark;
+
+	/* Clear and enable Rx full interrupt. */
+	xiic_irq_clr(priv, XIIC_INTR_RX_FULL_MASK | XIIC_INTR_TX_ERROR_MASK);
+
+	/* we want to get all but last byte, because the TX_ERROR IRQ is used
+	 * to inidicate error ACK on the address, and negative ack on the last
+	 * received byte, so to not mix them receive all but last.
+	 * In the case where there is only one byte to receive
+	 * we can check if ERROR and RX full is set at the same time
+	 */
+	rx_watermark = msg->len;
+	if (rx_watermark > IIC_RX_FIFO_DEPTH)
+		rx_watermark = IIC_RX_FIFO_DEPTH;
+
+	writeb(rx_watermark - 1, priv->base + XIIC_RFD_REG_OFFSET);
+
+	xilinx_xiic_set_addr(dev, msg->addr, msg->flags, msg->len, nmsgs);
+
+	xiic_irq_clr(priv, XIIC_INTR_BNB_MASK);
+
+	writew((msg->len & 0xff) | ((nmsgs == 1) ? XIIC_TX_DYN_STOP_MASK : 0),
+	       priv->base + XIIC_DTR_REG_OFFSET);
+
+	if (nmsgs == 1)
+		/* very last, enable bus not busy as well */
+		xiic_irq_clr(priv, XIIC_INTR_BNB_MASK);
+
+	return xiic_read_rx(priv, msg, nmsgs);
+}
+
+static int xilinx_xiic_write_common(struct udevice *dev, struct i2c_msg *msg,
+				    int nmsgs)
+{
+	struct xilinx_xiic_priv *priv = dev_get_priv(dev);
+	int ret;
+
+	xilinx_xiic_set_addr(dev, msg->addr, msg->flags, msg->len, nmsgs);
+	xiic_fill_tx_fifo(priv, msg, nmsgs);
+
+	ret = wait_for_bit_8(priv->base + XIIC_SR_REG_OFFSET,
+			     XIIC_SR_TX_FIFO_EMPTY_MASK, false, 1000, true);
+	if (ret)
+		return ret;
+
+	/* Clear any pending Tx empty, Tx Error and then enable them. */
+	xiic_irq_clr(priv, XIIC_INTR_TX_EMPTY_MASK | XIIC_INTR_TX_ERROR_MASK |
+			   XIIC_INTR_BNB_MASK);
+
+	return 0;
+}
+
+static void xiic_clear_rx_fifo(struct xilinx_xiic_priv *priv)
+{
+	u8 sr;
+
+	for (sr = readb(priv->base + XIIC_SR_REG_OFFSET);
+		!(sr & XIIC_SR_RX_FIFO_EMPTY_MASK);
+		sr = readb(priv->base + XIIC_SR_REG_OFFSET))
+		readb(priv->base + XIIC_DRR_REG_OFFSET);
+}
+
+static void xiic_reinit(struct xilinx_xiic_priv *priv)
+{
+	writel(XIIC_RESET_MASK, priv->base + XIIC_RESETR_OFFSET);
+
+	/* Set receive Fifo depth to maximum (zero based). */
+	writeb(IIC_RX_FIFO_DEPTH - 1, priv->base + XIIC_RFD_REG_OFFSET);
+
+	/* Reset Tx Fifo. */
+	writeb(XIIC_CR_TX_FIFO_RESET_MASK, priv->base + XIIC_CR_REG_OFFSET);
+
+	/* Enable IIC Device, remove Tx Fifo reset & disable general call. */
+	writeb(XIIC_CR_ENABLE_DEVICE_MASK, priv->base + XIIC_CR_REG_OFFSET);
+
+	/* make sure RX fifo is empty */
+	xiic_clear_rx_fifo(priv);
+
+	/* Disable interrupts */
+	writel(0, priv->base + XIIC_DGIER_OFFSET);
+
+	xiic_irq_clr(priv, XIIC_INTR_ARB_LOST_MASK);
+}
+
+static int xilinx_xiic_xfer(struct udevice *dev, struct i2c_msg *msg, int nmsgs)
+{
+	int ret = 0;
+
+	for (; nmsgs > 0; nmsgs--, msg++) {
+		if (msg->flags & I2C_M_RD)
+			ret = xilinx_xiic_read_common(dev, msg, nmsgs);
+		else
+			ret = xilinx_xiic_write_common(dev, msg, nmsgs);
+
+		if (ret)
+			return -EREMOTEIO;
+	}
+
+	return ret;
+}
+
+static int xilinx_xiic_probe_chip(struct udevice *dev, uint addr, uint flags)
+{
+	struct xilinx_xiic_priv *priv = dev_get_priv(dev);
+	u32 reg;
+	int ret;
+
+	xiic_reinit(priv);
+
+	xilinx_xiic_set_addr(dev, addr, 0, 0, 1);
+	ret = wait_for_bit_8(priv->base + XIIC_SR_REG_OFFSET,
+			     XIIC_SR_BUS_BUSY_MASK, false, 1000, true);
+	if (ret)
+		return ret;
+
+	reg = readl(priv->base + XIIC_IISR_OFFSET);
+	if (reg & XIIC_INTR_TX_ERROR_MASK)
+		return -ENODEV;
+
+	return 0;
+}
+
+static int xilinx_xiic_set_speed(struct udevice *dev, uint speed)
+{
+	return 0;
+}
+
+static int xilinx_xiic_probe(struct udevice *dev)
+{
+	struct xilinx_xiic_priv *priv = dev_get_priv(dev);
+
+	priv->base = dev_read_addr_ptr(dev);
+
+	writel(XIIC_CR_TX_FIFO_RESET_MASK, priv->base + XIIC_CR_REG_OFFSET);
+	xiic_reinit(priv);
+
+	return 0;
+}
+
+static const struct dm_i2c_ops xilinx_xiic_ops = {
+	.xfer		= xilinx_xiic_xfer,
+	.probe_chip	= xilinx_xiic_probe_chip,
+	.set_bus_speed	= xilinx_xiic_set_speed,
+};
+
+static const struct udevice_id xilinx_xiic_ids[] = {
+	{ .compatible = "xlnx,xps-iic-2.00.a" },
+	{ }
+};
+
+U_BOOT_DRIVER(xilinx_xiic) = {
+	.name		= "xilinx_axi_i2c",
+	.id		= UCLASS_I2C,
+	.of_match	= xilinx_xiic_ids,
+	.probe		= xilinx_xiic_probe,
+	.priv_auto_alloc_size = sizeof(struct xilinx_xiic_priv),
+	.ops		= &xilinx_xiic_ops,
+};