soc/intel/common: Add LPSS I2C driver

Add a generic LPSS I2C driver for Intel SOCs that use the Synopsys
DesignWare I2C block and have a similar configuration of that block.

This driver is ported from the Chromium depthcharge project where it
was ported from U-Boot originally, though it looks very different now.
From depthcharge it has been modified to fit into the coreboot I2C
driver model with platform_i2c_transfer() and use coreboot semantics
throughout including the stopwatch API for timeouts.

In order for this shared driver to work the SOC must:

1) Define CONFIG_SOC_INTEL_COMMON_LPSS_I2C_CLOCK_MHZ to set the clock
speed that the I2C controller core is running at.

2) Define the lpss_i2c_base_address() function to return the base
address for the specified bus.  This could be either done by looking
up the PCI device or a static table if the controllers are not PCI
devices and just have a static base address.

The driver is usable in verstage/romstage/ramstage, though it does
require early initialization of the controller to set a temporary base
address if it is used outside of ramstage.

This has been tested on Broadwell and Skylake SOCs in both pre-RAM and
ramstage environments by reading and writing both single bytes across
multiple segments as well as large blocks of data at once and with
different configured bus speeds.

While it does need specific configuration for each SOC this driver
should be able to work on all Intel SOCs currently in src/soc/intel.

Change-Id: Ibe492e53c45edb1d1745ec75e1ff66004081717e
Signed-off-by: Duncan Laurie <dlaurie@chromium.org>
Reviewed-on: https://review.coreboot.org/15101
Tested-by: build bot (Jenkins)
Reviewed-by: Aaron Durbin <adurbin@chromium.org>

4 files changed, 438 insertions, 0 deletions

diff --git a/src/soc/intel/common/Kconfig b/src/soc/intel/common/Kconfig
index e64aabf426..fdd8f0436e 100644
--- a/src/soc/intel/common/Kconfig
+++ b/src/soc/intel/common/Kconfig
@@ -41,6 +41,21 @@ config SOC_INTEL_COMMON_ACPI_WAKE_SOURCE
 	bool
 	default n
 
+config SOC_INTEL_COMMON_LPSS_I2C
+	bool
+	default n
+	help
+	  This driver supports the Intel Low Power Subsystem (LPSS) I2C
+	  controllers that are based on Synopsys DesignWare IP.
+
+config SOC_INTEL_COMMON_LPSS_I2C_CLOCK_MHZ
+	int
+	depends on SOC_INTEL_COMMON_LPSS_I2C
+	help
+	  The clock speed that the I2C controller is running at, in MHz.
+	  No default is set here as this is an SOC-specific value and must
+	  be provided by the SOC when it selects this driver.
+
 config SOC_SETS_MTRRS
 	bool
 	default n
diff --git a/src/soc/intel/common/Makefile.inc b/src/soc/intel/common/Makefile.inc
index 8e4a7936a5..88d5fd2c78 100644
--- a/src/soc/intel/common/Makefile.inc
+++ b/src/soc/intel/common/Makefile.inc
@@ -1,8 +1,10 @@
 ifeq ($(CONFIG_SOC_INTEL_COMMON),y)
 
+verstage-$(CONFIG_SOC_INTEL_COMMON_LPSS_I2C) += lpss_i2c.c
 verstage-$(CONFIG_SOC_INTEL_COMMON_RESET) += reset.c
 
 romstage-$(CONFIG_CACHE_MRC_SETTINGS) += mrc_cache.c
+romstage-$(CONFIG_SOC_INTEL_COMMON_LPSS_I2C) += lpss_i2c.c
 romstage-$(CONFIG_SOC_INTEL_COMMON_RESET) += reset.c
 romstage-y += util.c
 romstage-$(CONFIG_MMA) += mma.c
@@ -10,6 +12,7 @@ romstage-$(CONFIG_MMA) += mma.c
 ramstage-y += hda_verb.c
 ramstage-$(CONFIG_CACHE_MRC_SETTINGS) += mrc_cache.c
 ramstage-$(CONFIG_CACHE_MRC_SETTINGS) += nvm.c
+ramstage-$(CONFIG_SOC_INTEL_COMMON_LPSS_I2C) += lpss_i2c.c
 ramstage-$(CONFIG_SOC_INTEL_COMMON_RESET) += reset.c
 ramstage-y += util.c
 ramstage-$(CONFIG_MMA) += mma.c
diff --git a/src/soc/intel/common/lpss_i2c.c b/src/soc/intel/common/lpss_i2c.c
new file mode 100644
index 0000000000..2ac8e667c7
--- /dev/null
+++ b/src/soc/intel/common/lpss_i2c.c
@@ -0,0 +1,379 @@
+/*
+ * This file is part of the coreboot project.
+ *
+ * Copyright 2009 Vipin Kumar, ST Microelectronics
+ * Copyright 2016 Google Inc.
+ *
+ * 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; version 2 of the License.
+ *
+ * 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 <arch/io.h>
+#include <commonlib/helpers.h>
+#include <console/console.h>
+#include <device/device.h>
+#include <device/i2c.h>
+#include <timer.h>
+#include "lpss_i2c.h"
+
+struct lpss_i2c_regs {
+	uint32_t control;
+	uint32_t target_addr;
+	uint32_t slave_addr;
+	uint32_t master_addr;
+	uint32_t cmd_data;
+	uint32_t ss_scl_hcnt;
+	uint32_t ss_scl_lcnt;
+	uint32_t fs_scl_hcnt;
+	uint32_t fs_scl_lcnt;
+	uint32_t hs_scl_hcnt;
+	uint32_t hs_scl_lcnt;
+	uint32_t intr_stat;
+	uint32_t intr_mask;
+	uint32_t raw_intr_stat;
+	uint32_t rx_thresh;
+	uint32_t tx_thresh;
+	uint32_t clear_intr;
+	uint32_t clear_rx_under_intr;
+	uint32_t clear_rx_over_intr;
+	uint32_t clear_tx_over_intr;
+	uint32_t clear_rd_req_intr;
+	uint32_t clear_tx_abrt_intr;
+	uint32_t clear_rx_done_intr;
+	uint32_t clear_activity_intr;
+	uint32_t clear_stop_det_intr;
+	uint32_t clear_start_det_intr;
+	uint32_t clear_gen_call_intr;
+	uint32_t enable;
+	uint32_t status;
+	uint32_t tx_level;
+	uint32_t rx_level;
+	uint32_t sda_hold;
+	uint32_t tx_abort_source;
+} __attribute__((packed));
+
+/* Use a ~2ms timeout for various operations */
+#define LPSS_I2C_TIMEOUT_US		2000
+
+/* High and low times in different speed modes (in ns) */
+enum {
+	/* Standard Speed */
+	MIN_SS_SCL_HIGHTIME		= 4000,
+	MIN_SS_SCL_LOWTIME		= 4700,
+	/* Fast/Fast+ Speed */
+	MIN_FS_SCL_HIGHTIME		= 600,
+	MIN_FS_SCL_LOWTIME		= 1300,
+	/* High Speed */
+	MIN_HS_SCL_HIGHTIME		= 60,
+	MIN_HS_SCL_LOWTIME		= 160,
+};
+
+/* Control register definitions */
+enum {
+	CONTROL_MASTER_MODE		= (1 << 0),
+	CONTROL_SPEED_SS		= (1 << 1),
+	CONTROL_SPEED_FS		= (1 << 2),
+	CONTROL_SPEED_HS		= (3 << 1),
+	CONTROL_SPEED_MASK		= (3 << 1),
+	CONTROL_10BIT_SLAVE		= (1 << 3),
+	CONTROL_10BIT_MASTER		= (1 << 4),
+	CONTROL_RESTART_ENABLE		= (1 << 5),
+	CONTROL_SLAVE_DISABLE		= (1 << 6),
+};
+
+/* Command/Data register definitions */
+enum {
+	CMD_DATA_CMD			= (1 << 8),
+	CMD_DATA_STOP			= (1 << 9),
+};
+
+/* Status register definitions */
+enum {
+	STATUS_ACTIVITY			= (1 << 0),
+	STATUS_TX_FIFO_NOT_FULL		= (1 << 1),
+	STATUS_TX_FIFO_EMPTY		= (1 << 2),
+	STATUS_RX_FIFO_NOT_EMPTY	= (1 << 3),
+	STATUS_RX_FIFO_FULL		= (1 << 4),
+	STATUS_MASTER_ACTIVITY		= (1 << 5),
+	STATUS_SLAVE_ACTIVITY		= (1 << 6),
+};
+
+/* Enable register definitions */
+enum {
+	ENABLE_CONTROLLER		= (1 << 0),
+};
+
+/* Interrupt status register definitions */
+enum {
+	INTR_STAT_RX_UNDER		= (1 << 0),
+	INTR_STAT_RX_OVER		= (1 << 1),
+	INTR_STAT_RX_FULL		= (1 << 2),
+	INTR_STAT_TX_OVER		= (1 << 3),
+	INTR_STAT_TX_EMPTY		= (1 << 4),
+	INTR_STAT_RD_REQ		= (1 << 5),
+	INTR_STAT_TX_ABORT		= (1 << 6),
+	INTR_STAT_RX_DONE		= (1 << 7),
+	INTR_STAT_ACTIVITY		= (1 << 8),
+	INTR_STAT_STOP_DET		= (1 << 9),
+	INTR_STAT_START_DET		= (1 << 10),
+	INTR_STAT_GEN_CALL		= (1 << 11),
+};
+
+/* Enable this I2C controller */
+static void lpss_i2c_enable(struct lpss_i2c_regs *regs)
+{
+	uint32_t enable = read32(&regs->enable);
+
+	if (!(enable & ENABLE_CONTROLLER))
+		write32(&regs->enable, enable | ENABLE_CONTROLLER);
+}
+
+/* Disable this I2C controller */
+static int lpss_i2c_disable(struct lpss_i2c_regs *regs)
+{
+	uint32_t enable = read32(&regs->enable);
+
+	if (enable & ENABLE_CONTROLLER) {
+		struct stopwatch sw;
+
+		write32(&regs->enable, enable & ~ENABLE_CONTROLLER);
+
+		/* Wait for enable bit to clear */
+		stopwatch_init_usecs_expire(&sw, LPSS_I2C_TIMEOUT_US);
+		while (read32(&regs->enable) & ENABLE_CONTROLLER)
+			if (stopwatch_expired(&sw))
+				return -1;
+	}
+
+	return 0;
+}
+
+/* Wait for this I2C controller to go idle for transmit */
+static int lpss_i2c_wait_for_bus_idle(struct lpss_i2c_regs *regs)
+{
+	struct stopwatch sw;
+
+	/* Start timeout for up to 16 bytes in FIFO */
+	stopwatch_init_usecs_expire(&sw, 16 * LPSS_I2C_TIMEOUT_US);
+
+	while (!stopwatch_expired(&sw)) {
+		uint32_t status = read32(&regs->status);
+
+		/* Check for master activity and keep waiting */
+		if (status & STATUS_MASTER_ACTIVITY)
+			continue;
+
+		/* Check for TX FIFO empty to indicate TX idle */
+		if (status & STATUS_TX_FIFO_EMPTY)
+			return 0;
+	}
+
+	/* Timed out while waiting for bus to go idle */
+	return -1;
+}
+
+/* Transfer one byte of one segment, sending stop bit if requested */
+static int lpss_i2c_transfer_byte(struct lpss_i2c_regs *regs,
+				  struct i2c_seg *segment,
+				  size_t byte, int send_stop)
+{
+	struct stopwatch sw;
+	uint32_t cmd = CMD_DATA_CMD; /* Read op */
+
+	stopwatch_init_usecs_expire(&sw, LPSS_I2C_TIMEOUT_US);
+
+	if (!segment->read) {
+		/* Write op only: Wait for FIFO not full */
+		while (!(read32(&regs->status) & STATUS_TX_FIFO_NOT_FULL)) {
+			if (stopwatch_expired(&sw)) {
+				printk(BIOS_ERR, "I2C transmit timeout\n");
+				return -1;
+			}
+		}
+		cmd = segment->buf[byte];
+	}
+
+	/* Send stop on last byte, if desired */
+	if (send_stop && byte == segment->len - 1)
+		cmd |= CMD_DATA_STOP;
+
+	write32(&regs->cmd_data, cmd);
+
+	if (segment->read) {
+		/* Read op only: Wait for FIFO data and store it */
+		while (!(read32(&regs->status) & STATUS_RX_FIFO_NOT_EMPTY)) {
+			if (stopwatch_expired(&sw)) {
+				printk(BIOS_ERR, "I2C receive timeout\n");
+				return -1;
+			}
+		}
+		segment->buf[byte] = read32(&regs->cmd_data);
+	}
+
+	return 0;
+}
+
+/* Global I2C bus handler, defined in include/i2c.h */
+int platform_i2c_transfer(unsigned bus, struct i2c_seg *segments, int count)
+{
+	struct stopwatch sw;
+	struct lpss_i2c_regs *regs;
+	size_t byte;
+
+	if (count <= 0 || !segments)
+		return -1;
+
+	regs = (struct lpss_i2c_regs *)lpss_i2c_base_address(bus);
+	if (!regs) {
+		printk(BIOS_ERR, "I2C bus %u base address not found\n", bus);
+		return -1;
+	}
+
+	if (!(read32(&regs->enable) & ENABLE_CONTROLLER)) {
+		printk(BIOS_ERR, "I2C bus %u not initialized\n", bus);
+		return -1;
+	}
+
+	if (lpss_i2c_wait_for_bus_idle(regs)) {
+		printk(BIOS_ERR, "I2C timeout waiting for bus %u idle\n", bus);
+		return -1;
+	}
+
+	/* Process each segment */
+	while (count--) {
+		/* Set target slave address */
+		write32(&regs->target_addr, segments->chip);
+
+		/* Read or write each byte in segment */
+		for (byte = 0; byte < segments->len; byte++) {
+			/*
+			 * Set stop condition on final segment only.
+			 * Repeated start will be automatically generated
+			 * by the controller on R->W or W->R switch.
+			 */
+			if (lpss_i2c_transfer_byte(regs, segments, byte,
+						   count == 0) < 0) {
+				printk(BIOS_ERR, "I2C %s failed: bus %u "
+				       "addr 0x%02x\n", segments->read ?
+				       "read" : "write", bus, segments->chip);
+				return -1;
+			}
+		}
+		segments++;
+	}
+
+	/* Wait for interrupt status to indicate transfer is complete */
+	stopwatch_init_usecs_expire(&sw, LPSS_I2C_TIMEOUT_US);
+	while (!(read32(&regs->raw_intr_stat) & INTR_STAT_STOP_DET)) {
+		if (stopwatch_expired(&sw)) {
+			printk(BIOS_ERR, "I2C stop bit not received\n");
+			return -1;
+		}
+	}
+
+	/* Read to clear INTR_STAT_STOP_DET */
+	read32(&regs->clear_stop_det_intr);
+
+	/* Wait for the bus to go idle */
+	if (lpss_i2c_wait_for_bus_idle(regs)) {
+		printk(BIOS_ERR, "I2C timeout waiting for bus %u idle\n", bus);
+		return -1;
+	}
+
+	/* Flush the RX FIFO in case it is not empty */
+	stopwatch_init_usecs_expire(&sw, 16 * LPSS_I2C_TIMEOUT_US);
+	while (read32(&regs->status) & STATUS_RX_FIFO_NOT_EMPTY) {
+		if (stopwatch_expired(&sw)) {
+			printk(BIOS_ERR, "I2C timeout flushing RX FIFO\n");
+			return -1;
+		}
+		read32(&regs->cmd_data);
+	}
+
+	return 0;
+}
+
+static void lpss_i2c_set_speed(struct lpss_i2c_regs *regs, enum i2c_speed speed)
+{
+	const int ic_clk = CONFIG_SOC_INTEL_COMMON_LPSS_I2C_CLOCK_MHZ;
+	uint32_t control, hcnt_min, lcnt_min;
+	void *hcnt_reg, *lcnt_reg;
+
+	/* Clock must be provided by Kconfig */
+	if (!ic_clk || !speed)
+		return;
+
+	control = read32(&regs->control);
+	control &= ~CONTROL_SPEED_MASK;
+
+	if (speed >= I2C_SPEED_HIGH) {
+		/* High Speed */
+		control |= CONTROL_SPEED_HS;
+		hcnt_reg = &regs->hs_scl_hcnt;
+		lcnt_reg = &regs->hs_scl_lcnt;
+		hcnt_min = MIN_HS_SCL_HIGHTIME;
+		lcnt_min = MIN_HS_SCL_LOWTIME;
+	} else if (speed >= I2C_SPEED_FAST) {
+		/* Fast Speed */
+		control |= CONTROL_SPEED_FS;
+		hcnt_reg = &regs->fs_scl_hcnt;
+		lcnt_reg = &regs->fs_scl_lcnt;
+		hcnt_min = MIN_FS_SCL_HIGHTIME;
+		lcnt_min = MIN_FS_SCL_LOWTIME;
+	} else {
+		/* Standard Speed */
+		control |= CONTROL_SPEED_SS;
+		hcnt_reg = &regs->ss_scl_hcnt;
+		lcnt_reg = &regs->ss_scl_lcnt;
+		hcnt_min = MIN_SS_SCL_HIGHTIME;
+		lcnt_min = MIN_SS_SCL_LOWTIME;
+	}
+
+	/* Select this speed in the control register */
+	write32(&regs->control, control);
+
+	/* SCL count must be set after the speed is selected */
+	write32(hcnt_reg, ic_clk * hcnt_min / KHz);
+	write32(lcnt_reg, ic_clk * lcnt_min / KHz);
+}
+
+void lpss_i2c_init(unsigned bus, enum i2c_speed speed)
+{
+	struct lpss_i2c_regs *regs;
+
+	regs = (struct lpss_i2c_regs *)lpss_i2c_base_address(bus);
+	if (!regs) {
+		printk(BIOS_ERR, "I2C bus %u base address not found\n", bus);
+		return;
+	}
+
+	if (lpss_i2c_disable(regs) < 0) {
+		printk(BIOS_ERR, "I2C timeout disabling bus %u\n", bus);
+		return;
+	}
+
+	/* Put controller in master mode with restart enabled */
+	write32(&regs->control, CONTROL_MASTER_MODE | CONTROL_SLAVE_DISABLE |
+		CONTROL_RESTART_ENABLE);
+
+	/* Set bus speed to FAST by default */
+	lpss_i2c_set_speed(regs, speed ? : I2C_SPEED_FAST);
+
+	/* Set RX/TX thresholds to smallest values */
+	write32(&regs->rx_thresh, 0);
+	write32(&regs->tx_thresh, 0);
+
+	/* Enable stop detection interrupt */
+	write32(&regs->intr_mask, INTR_STAT_STOP_DET);
+
+	lpss_i2c_enable(regs);
+
+	printk(BIOS_INFO, "LPSS I2C bus %u at 0x%p (%u KHz)\n",
+	       bus, regs, (speed ? : I2C_SPEED_FAST) / KHz);
+}
diff --git a/src/soc/intel/common/lpss_i2c.h b/src/soc/intel/common/lpss_i2c.h
new file mode 100644
index 0000000000..82594147fd
--- /dev/null
+++ b/src/soc/intel/common/lpss_i2c.h
@@ -0,0 +1,41 @@
+/*
+ * This file is part of the coreboot project.
+ *
+ * Copyright 2016 Google Inc.
+ *
+ * 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; version 2 of the License.
+ *
+ * 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.
+ */
+
+#ifndef SOC_INTEL_COMMON_LPSS_I2C_H
+#define SOC_INTEL_COMMON_LPSS_I2C_H
+
+#include <device/i2c.h>
+#include <stdint.h>
+
+/*
+ * Return the base address for this bus controller.
+ *
+ * This function *must* be implemented by the SOC and return the appropriate
+ * base address for the I2C registers that correspond to the provided bus.
+ */
+uintptr_t lpss_i2c_base_address(unsigned bus);
+
+/*
+ * Initialize this bus controller and set the speed.
+ *
+ * The bus speed can be passed in Hz or using values from device/i2c.h and
+ * will default to I2C_SPEED_FAST if it is not provided.
+ *
+ * The SOC *must* define CONFIG_SOC_INTEL_COMMON_LPSS_I2C_CLOCK for the
+ * bus speed calculation to be correct.
+ */
+void lpss_i2c_init(unsigned bus, enum i2c_speed speed);
+
+#endif