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/* SPDX-License-Identifier: Apache-2.0 */
/*
* Copyright © 2023 Calian Ltd. All rights reserved.
*
* Driver for the Xilinx AXI IIC Bus Interface.
* This is an FPGA logic core as described by Xilinx document PG090.
*/
#include <errno.h>
#include <zephyr/drivers/i2c.h>
#include <zephyr/sys/util.h>
#include <zephyr/logging/log.h>
#include <zephyr/irq.h>
LOG_MODULE_REGISTER(i2c_xilinx_axi, CONFIG_I2C_LOG_LEVEL);
#include "i2c-priv.h"
#include "i2c_xilinx_axi.h"
struct i2c_xilinx_axi_config {
mem_addr_t base;
void (*irq_config_func)(const struct device *dev);
/* Whether device has working dynamic read (broken prior to core rev. 2.1) */
bool dyn_read_working;
};
struct i2c_xilinx_axi_data {
struct k_event irq_event;
/* Serializes between ISR and other calls */
struct k_spinlock lock;
/* Provides exclusion against multiple concurrent requests */
struct k_mutex mutex;
#if defined(CONFIG_I2C_TARGET)
struct i2c_target_config *target_cfg;
bool target_reading;
bool target_read_aborted;
bool target_writing;
#endif
};
#if defined(CONFIG_I2C_TARGET)
#define I2C_XILINX_AXI_TARGET_INTERRUPTS \
(ISR_ADDR_TARGET | ISR_NOT_ADDR_TARGET | ISR_RX_FIFO_FULL | ISR_TX_FIFO_EMPTY | \
ISR_TX_ERR_TARGET_COMP)
static int i2c_xilinx_axi_target_register(const struct device *dev, struct i2c_target_config *cfg)
{
const struct i2c_xilinx_axi_config *config = dev->config;
struct i2c_xilinx_axi_data *data = dev->data;
k_spinlock_key_t key;
uint32_t int_enable;
uint32_t int_status;
int ret;
if (cfg->flags & I2C_TARGET_FLAGS_ADDR_10_BITS) {
/* Optionally supported in core, but not implemented in driver yet */
return -EOPNOTSUPP;
}
k_mutex_lock(&data->mutex, K_FOREVER);
key = k_spin_lock(&data->lock);
if (data->target_cfg) {
ret = -EBUSY;
goto out_unlock;
}
data->target_cfg = cfg;
int_status = sys_read32(config->base + REG_ISR);
if (int_status & I2C_XILINX_AXI_TARGET_INTERRUPTS) {
sys_write32(int_status & I2C_XILINX_AXI_TARGET_INTERRUPTS, config->base + REG_ISR);
}
sys_write32(CR_EN, config->base + REG_CR);
int_enable = sys_read32(config->base + REG_IER);
int_enable |= ISR_ADDR_TARGET;
sys_write32(int_enable, config->base + REG_IER);
sys_write32(cfg->address << 1, config->base + REG_ADR);
sys_write32(0, config->base + REG_RX_FIFO_PIRQ);
ret = 0;
out_unlock:
k_spin_unlock(&data->lock, key);
LOG_DBG("Target register ret=%d", ret);
k_mutex_unlock(&data->mutex);
return ret;
}
static int i2c_xilinx_axi_target_unregister(const struct device *dev, struct i2c_target_config *cfg)
{
const struct i2c_xilinx_axi_config *config = dev->config;
struct i2c_xilinx_axi_data *data = dev->data;
k_spinlock_key_t key;
uint32_t int_enable;
int ret;
k_mutex_lock(&data->mutex, K_FOREVER);
key = k_spin_lock(&data->lock);
if (!data->target_cfg) {
ret = -EINVAL;
goto out_unlock;
}
if (data->target_reading || data->target_writing) {
ret = -EBUSY;
goto out_unlock;
}
data->target_cfg = NULL;
sys_write32(0, config->base + REG_ADR);
sys_write32(CR_EN, config->base + REG_CR);
int_enable = sys_read32(config->base + REG_IER);
int_enable &= ~I2C_XILINX_AXI_TARGET_INTERRUPTS;
sys_write32(int_enable, config->base + REG_IER);
ret = 0;
out_unlock:
k_spin_unlock(&data->lock, key);
LOG_DBG("Target unregister ret=%d", ret);
k_mutex_unlock(&data->mutex);
return ret;
}
static void i2c_xilinx_axi_target_isr(const struct i2c_xilinx_axi_config *config,
struct i2c_xilinx_axi_data *data, uint32_t int_status,
uint32_t *ints_to_clear, uint32_t *int_enable)
{
if (int_status & ISR_ADDR_TARGET) {
LOG_DBG("Addressed as target");
*int_enable &= ~ISR_ADDR_TARGET;
*int_enable |= ISR_NOT_ADDR_TARGET;
*ints_to_clear |= ISR_NOT_ADDR_TARGET;
if (sys_read32(config->base + REG_SR) & SR_SRW) {
uint8_t read_byte;
data->target_reading = true;
*ints_to_clear |= ISR_TX_FIFO_EMPTY | ISR_TX_ERR_TARGET_COMP;
*int_enable |= ISR_TX_FIFO_EMPTY | ISR_TX_ERR_TARGET_COMP;
if ((*data->target_cfg->callbacks->read_requested)(data->target_cfg,
&read_byte)) {
LOG_DBG("target read_requested rejected");
data->target_read_aborted = true;
read_byte = 0xFF;
}
sys_write32(read_byte, config->base + REG_TX_FIFO);
} else {
data->target_writing = true;
*int_enable |= ISR_RX_FIFO_FULL;
if ((*data->target_cfg->callbacks->write_requested)(data->target_cfg)) {
uint32_t cr = sys_read32(config->base + REG_CR);
LOG_DBG("target write_requested rejected");
cr |= CR_TXAK;
sys_write32(cr, config->base + REG_CR);
}
}
} else if (int_status & ISR_NOT_ADDR_TARGET) {
LOG_DBG("Not addressed as target");
(*data->target_cfg->callbacks->stop)(data->target_cfg);
data->target_reading = false;
data->target_read_aborted = false;
data->target_writing = false;
sys_write32(CR_EN, config->base + REG_CR);
*int_enable &= ~I2C_XILINX_AXI_TARGET_INTERRUPTS;
*int_enable |= ISR_ADDR_TARGET;
*ints_to_clear |= ISR_ADDR_TARGET;
} else if (int_status & ISR_RX_FIFO_FULL) {
const uint8_t written_byte =
sys_read32(config->base + REG_RX_FIFO) & RX_FIFO_DATA_MASK;
if ((*data->target_cfg->callbacks->write_received)(data->target_cfg,
written_byte)) {
uint32_t cr = sys_read32(config->base + REG_CR);
LOG_DBG("target write_received rejected");
cr |= CR_TXAK;
sys_write32(cr, config->base + REG_CR);
}
} else if (int_status & ISR_TX_ERR_TARGET_COMP) {
if (data->target_reading) {
/* Controller has NAKed the last byte read, so no more to send.
* Ignore TX FIFO empty so we don't write an extra byte.
*/
LOG_DBG("target read completed");
*int_enable &= ~ISR_TX_FIFO_EMPTY;
*ints_to_clear |= ISR_TX_FIFO_EMPTY;
} else {
LOG_WRN("Unexpected TX complete");
}
} else if (int_status & ISR_TX_FIFO_EMPTY) {
if (data->target_reading) {
uint8_t read_byte = 0xFF;
if (!data->target_read_aborted &&
(*data->target_cfg->callbacks->read_processed)(data->target_cfg,
&read_byte)) {
LOG_DBG("target read_processed rejected");
data->target_read_aborted = true;
}
sys_write32(read_byte, config->base + REG_TX_FIFO);
} else {
LOG_WRN("Unexpected TX empty");
}
}
}
#endif
static void i2c_xilinx_axi_isr(const struct device *dev)
{
const struct i2c_xilinx_axi_config *config = dev->config;
struct i2c_xilinx_axi_data *data = dev->data;
const k_spinlock_key_t key = k_spin_lock(&data->lock);
uint32_t int_enable = sys_read32(config->base + REG_IER);
const uint32_t int_status = sys_read32(config->base + REG_ISR) & int_enable;
uint32_t ints_to_clear = int_status;
uint32_t ints_to_mask = int_status;
LOG_DBG("ISR called for 0x%08" PRIxPTR ", status 0x%02x", config->base, int_status);
if (int_status & ISR_ARB_LOST) {
/* Must clear MSMS before clearing interrupt */
uint32_t cr = sys_read32(config->base + REG_CR);
cr &= ~CR_MSMS;
sys_write32(cr, config->base + REG_CR);
}
#if defined(CONFIG_I2C_TARGET)
if (data->target_cfg && (int_status & I2C_XILINX_AXI_TARGET_INTERRUPTS)) {
ints_to_mask &= ~(int_status & I2C_XILINX_AXI_TARGET_INTERRUPTS);
i2c_xilinx_axi_target_isr(config, data, int_status, &ints_to_clear, &int_enable);
}
#endif
sys_write32(int_enable & ~ints_to_mask, config->base + REG_IER);
/* Be careful, writing 1 to a bit that is not currently set in ISR will SET it! */
sys_write32(ints_to_clear & sys_read32(config->base + REG_ISR), config->base + REG_ISR);
k_spin_unlock(&data->lock, key);
k_event_post(&data->irq_event, int_status);
}
static void i2c_xilinx_axi_reinit(const struct i2c_xilinx_axi_config *config)
{
LOG_DBG("Controller reinit");
sys_write32(SOFTR_KEY, config->base + REG_SOFTR);
sys_write32(CR_TX_FIFO_RST, config->base + REG_CR);
sys_write32(CR_EN, config->base + REG_CR);
sys_write32(GIE_ENABLE, config->base + REG_GIE);
}
static int i2c_xilinx_axi_configure(const struct device *dev, uint32_t dev_config)
{
const struct i2c_xilinx_axi_config *config = dev->config;
LOG_INF("Configuring %s at 0x%08" PRIxPTR, dev->name, config->base);
i2c_xilinx_axi_reinit(config);
return 0;
}
static uint32_t i2c_xilinx_axi_wait_interrupt(const struct i2c_xilinx_axi_config *config,
struct i2c_xilinx_axi_data *data, uint32_t int_mask)
{
const k_spinlock_key_t key = k_spin_lock(&data->lock);
const uint32_t int_enable = sys_read32(config->base + REG_IER) | int_mask;
uint32_t events;
LOG_DBG("Set IER to 0x%02x", int_enable);
sys_write32(int_enable, config->base + REG_IER);
k_event_clear(&data->irq_event, int_mask);
k_spin_unlock(&data->lock, key);
events = k_event_wait(&data->irq_event, int_mask, false, K_MSEC(100));
LOG_DBG("Got ISR events 0x%02x", events);
if (!events) {
LOG_ERR("Timeout waiting for ISR events 0x%02x, SR 0x%02x, ISR 0x%02x", int_mask,
sys_read32(config->base + REG_SR), sys_read32(config->base + REG_ISR));
}
return events;
}
static void i2c_xilinx_axi_clear_interrupt(const struct i2c_xilinx_axi_config *config,
struct i2c_xilinx_axi_data *data, uint32_t int_mask)
{
const k_spinlock_key_t key = k_spin_lock(&data->lock);
const uint32_t int_status = sys_read32(config->base + REG_ISR);
if (int_status & int_mask) {
sys_write32(int_status & int_mask, config->base + REG_ISR);
}
k_spin_unlock(&data->lock, key);
}
static int i2c_xilinx_axi_wait_rx_full(const struct i2c_xilinx_axi_config *config,
struct i2c_xilinx_axi_data *data, uint32_t read_bytes)
{
uint32_t events;
i2c_xilinx_axi_clear_interrupt(config, data, ISR_RX_FIFO_FULL);
if (!(sys_read32(config->base + REG_SR) & SR_RX_FIFO_EMPTY) &&
(sys_read32(config->base + REG_RX_FIFO_OCY) & RX_FIFO_OCY_MASK) + 1 >= read_bytes) {
LOG_DBG("RX already full on checking, SR 0x%02x RXOCY 0x%02x",
sys_read32(config->base + REG_SR),
sys_read32(config->base + REG_RX_FIFO_OCY));
return 0;
}
events = i2c_xilinx_axi_wait_interrupt(config, data, ISR_RX_FIFO_FULL | ISR_ARB_LOST);
if (!events) {
return -ETIMEDOUT;
}
if (events & ISR_ARB_LOST) {
LOG_ERR("Arbitration lost on RX");
return -ENXIO;
}
return 0;
}
static int i2c_xilinx_axi_read_nondyn(const struct i2c_xilinx_axi_config *config,
struct i2c_xilinx_axi_data *data, struct i2c_msg *msg,
uint16_t addr)
{
uint8_t *read_ptr = msg->buf;
uint32_t bytes_left = msg->len;
uint32_t cr = CR_EN | CR_MSMS;
if (!bytes_left) {
return -EINVAL;
}
if (bytes_left == 1) {
/* Set TXAK bit now, to NAK after the first byte is received */
cr |= CR_TXAK;
}
/**
* The Xilinx core's RX FIFO full logic seems rather broken in that the interrupt
* is triggered, and the I2C receive is throttled, only when the FIFO occupancy
* equals the PIRQ threshold, not when greater or equal. In the non-dynamic mode
* of operation, we need to stop the read prior to the last bytes being received
* from the target in order to set the TXAK bit and clear MSMS to terminate the
* receive properly.
* However, if we previously allowed multiple bytes into the RX FIFO, this requires
* reducing the PIRQ threshold to 0 (single byte) during the receive operation. This
* can cause the receive to unthrottle (since FIFO occupancy now exceeds PIRQ
* threshold) and depending on timing between the driver code and the core,
* this can cause the core to try to receive more data into the FIFO than desired
* and cause various unexpected results.
*
* To avoid this, we only receive one byte at a time in the non-dynamic mode.
* Dynamic mode doesn't have this issue as it provides the RX byte count to the
* controller specifically and the TXAK and MSMS bits are handled automatically.
*/
sys_write32(0, config->base + REG_RX_FIFO_PIRQ);
if (msg->flags & I2C_MSG_RESTART) {
cr |= CR_RSTA;
sys_write32(cr, config->base + REG_CR);
sys_write32((addr << 1) | I2C_MSG_READ, config->base + REG_TX_FIFO);
} else {
sys_write32((addr << 1) | I2C_MSG_READ, config->base + REG_TX_FIFO);
sys_write32(cr, config->base + REG_CR);
}
while (bytes_left) {
int ret = i2c_xilinx_axi_wait_rx_full(config, data, 1);
if (ret) {
return ret;
}
if (bytes_left == 2) {
/* Set TXAK so the last byte is NAKed */
cr |= CR_TXAK;
} else if (bytes_left == 1 && (msg->flags & I2C_MSG_STOP)) {
/* Before reading the last byte, clear MSMS to issue a stop if required */
cr &= ~CR_MSMS;
}
cr &= ~CR_RSTA;
sys_write32(cr, config->base + REG_CR);
*read_ptr++ = sys_read32(config->base + REG_RX_FIFO) & RX_FIFO_DATA_MASK;
bytes_left--;
}
return 0;
}
static int i2c_xilinx_axi_read_dyn(const struct i2c_xilinx_axi_config *config,
struct i2c_xilinx_axi_data *data, struct i2c_msg *msg,
uint16_t addr)
{
uint8_t *read_ptr = msg->buf;
uint32_t bytes_left = msg->len;
uint32_t bytes_to_read = bytes_left;
uint32_t cr = CR_EN;
uint32_t len_word = bytes_left;
if (!bytes_left || bytes_left > MAX_DYNAMIC_READ_LEN) {
return -EINVAL;
}
if (msg->flags & I2C_MSG_RESTART) {
cr |= CR_MSMS | CR_RSTA;
}
sys_write32(cr, config->base + REG_CR);
if (bytes_to_read > FIFO_SIZE) {
bytes_to_read = FIFO_SIZE;
}
sys_write32(bytes_to_read - 1, config->base + REG_RX_FIFO_PIRQ);
sys_write32((addr << 1) | I2C_MSG_READ | TX_FIFO_START, config->base + REG_TX_FIFO);
if (msg->flags & I2C_MSG_STOP) {
len_word |= TX_FIFO_STOP;
}
sys_write32(len_word, config->base + REG_TX_FIFO);
while (bytes_left) {
int ret;
bytes_to_read = bytes_left;
if (bytes_to_read > FIFO_SIZE) {
bytes_to_read = FIFO_SIZE;
}
sys_write32(bytes_to_read - 1, config->base + REG_RX_FIFO_PIRQ);
ret = i2c_xilinx_axi_wait_rx_full(config, data, bytes_to_read);
if (ret) {
return ret;
}
while (bytes_to_read) {
*read_ptr++ = sys_read32(config->base + REG_RX_FIFO) & RX_FIFO_DATA_MASK;
bytes_to_read--;
bytes_left--;
}
}
return 0;
}
static int i2c_xilinx_axi_wait_tx_done(const struct i2c_xilinx_axi_config *config,
struct i2c_xilinx_axi_data *data)
{
const uint32_t finish_bits = ISR_BUS_NOT_BUSY | ISR_TX_FIFO_EMPTY;
uint32_t events = i2c_xilinx_axi_wait_interrupt(
config, data, finish_bits | ISR_TX_ERR_TARGET_COMP | ISR_ARB_LOST);
if (!(events & finish_bits) || (events & ~finish_bits)) {
if (!events) {
return -ETIMEDOUT;
}
if (events & ISR_ARB_LOST) {
LOG_ERR("Arbitration lost on TX");
return -EAGAIN;
}
LOG_ERR("TX received NAK");
return -ENXIO;
}
return 0;
}
static int i2c_xilinx_axi_wait_not_busy(const struct i2c_xilinx_axi_config *config,
struct i2c_xilinx_axi_data *data)
{
if (sys_read32(config->base + REG_SR) & SR_BB) {
uint32_t events = i2c_xilinx_axi_wait_interrupt(config, data, ISR_BUS_NOT_BUSY);
if (events != ISR_BUS_NOT_BUSY) {
LOG_ERR("Bus stuck busy");
i2c_xilinx_axi_reinit(config);
return -EBUSY;
}
}
return 0;
}
static int i2c_xilinx_axi_write(const struct i2c_xilinx_axi_config *config,
struct i2c_xilinx_axi_data *data, const struct i2c_msg *msg,
uint16_t addr)
{
const uint8_t *write_ptr = msg->buf;
uint32_t bytes_left = msg->len;
uint32_t cr = CR_EN | CR_TX;
uint32_t fifo_space = FIFO_SIZE - 1; /* account for address being written */
if (msg->flags & I2C_MSG_RESTART) {
cr |= CR_MSMS | CR_RSTA;
}
i2c_xilinx_axi_clear_interrupt(config, data, ISR_TX_ERR_TARGET_COMP | ISR_ARB_LOST);
sys_write32(cr, config->base + REG_CR);
sys_write32((addr << 1) | TX_FIFO_START, config->base + REG_TX_FIFO);
/* TX FIFO empty detection is somewhat fragile because the status register
* TX_FIFO_EMPTY bit can be set prior to the transaction actually being
* complete, so we have to rely on the TX empty interrupt.
* However, delays in writing data to the TX FIFO could cause it
* to run empty in the middle of the process, causing us to get a spurious
* completion detection from the interrupt. Therefore we disable interrupts
* while the TX FIFO is being filled up to try to avoid this.
*/
while (bytes_left) {
uint32_t bytes_to_send = bytes_left;
const k_spinlock_key_t key = k_spin_lock(&data->lock);
int ret;
if (bytes_to_send > fifo_space) {
bytes_to_send = fifo_space;
}
while (bytes_to_send) {
uint32_t write_word = *write_ptr++;
if (bytes_left == 1 && (msg->flags & I2C_MSG_STOP)) {
write_word |= TX_FIFO_STOP;
}
sys_write32(write_word, config->base + REG_TX_FIFO);
bytes_to_send--;
bytes_left--;
}
i2c_xilinx_axi_clear_interrupt(config, data, ISR_TX_FIFO_EMPTY | ISR_BUS_NOT_BUSY);
k_spin_unlock(&data->lock, key);
ret = i2c_xilinx_axi_wait_tx_done(config, data);
if (ret) {
return ret;
}
fifo_space = FIFO_SIZE;
}
return 0;
}
static int i2c_xilinx_axi_transfer(const struct device *dev, struct i2c_msg *msgs, uint8_t num_msgs,
uint16_t addr)
{
const struct i2c_xilinx_axi_config *config = dev->config;
struct i2c_xilinx_axi_data *data = dev->data;
int ret;
k_mutex_lock(&data->mutex, K_FOREVER);
/**
* Reinitializing before each transfer shouldn't technically be needed, but
* seems to improve general reliability. The Linux driver also does this.
*/
i2c_xilinx_axi_reinit(config);
ret = i2c_xilinx_axi_wait_not_busy(config, data);
if (ret) {
goto out_unlock;
}
if (!num_msgs) {
goto out_unlock;
}
do {
if (msgs->flags & I2C_MSG_ADDR_10_BITS) {
/* Optionally supported in core, but not implemented in driver yet */
ret = -EOPNOTSUPP;
goto out_unlock;
}
if (msgs->flags & I2C_MSG_READ) {
if (config->dyn_read_working && msgs->len <= MAX_DYNAMIC_READ_LEN) {
ret = i2c_xilinx_axi_read_dyn(config, data, msgs, addr);
} else {
ret = i2c_xilinx_axi_read_nondyn(config, data, msgs, addr);
}
} else {
ret = i2c_xilinx_axi_write(config, data, msgs, addr);
}
if (!ret && (msgs->flags & I2C_MSG_STOP)) {
ret = i2c_xilinx_axi_wait_not_busy(config, data);
}
if (ret) {
goto out_unlock;
}
msgs++;
num_msgs--;
} while (num_msgs);
out_unlock:
k_mutex_unlock(&data->mutex);
return ret;
}
static int i2c_xilinx_axi_init(const struct device *dev)
{
const struct i2c_xilinx_axi_config *config = dev->config;
struct i2c_xilinx_axi_data *data = dev->data;
int error;
k_event_init(&data->irq_event);
k_mutex_init(&data->mutex);
error = i2c_xilinx_axi_configure(dev, I2C_MODE_CONTROLLER);
if (error) {
return error;
}
config->irq_config_func(dev);
LOG_INF("initialized");
return 0;
}
static const struct i2c_driver_api i2c_xilinx_axi_driver_api = {
.configure = i2c_xilinx_axi_configure,
.transfer = i2c_xilinx_axi_transfer,
#if defined(CONFIG_I2C_TARGET)
.target_register = i2c_xilinx_axi_target_register,
.target_unregister = i2c_xilinx_axi_target_unregister,
#endif
};
#define I2C_XILINX_AXI_INIT(n, compat) \
static void i2c_xilinx_axi_config_func_##compat##_##n(const struct device *dev); \
\
static const struct i2c_xilinx_axi_config i2c_xilinx_axi_config_##compat##_##n = { \
.base = DT_INST_REG_ADDR(n), \
.irq_config_func = i2c_xilinx_axi_config_func_##compat##_##n, \
.dyn_read_working = DT_NODE_HAS_COMPAT(DT_DRV_INST(n), xlnx_xps_iic_2_1)}; \
\
static struct i2c_xilinx_axi_data i2c_xilinx_axi_data_##compat##_##n; \
\
I2C_DEVICE_DT_INST_DEFINE(n, i2c_xilinx_axi_init, NULL, \
&i2c_xilinx_axi_data_##compat##_##n, \
&i2c_xilinx_axi_config_##compat##_##n, POST_KERNEL, \
CONFIG_I2C_INIT_PRIORITY, &i2c_xilinx_axi_driver_api); \
\
static void i2c_xilinx_axi_config_func_##compat##_##n(const struct device *dev) \
{ \
ARG_UNUSED(dev); \
\
IRQ_CONNECT(DT_INST_IRQN(n), DT_INST_IRQ(n, priority), i2c_xilinx_axi_isr, \
DEVICE_DT_INST_GET(n), 0); \
\
irq_enable(DT_INST_IRQN(n)); \
}
#define DT_DRV_COMPAT xlnx_xps_iic_2_1
DT_INST_FOREACH_STATUS_OKAY_VARGS(I2C_XILINX_AXI_INIT, DT_DRV_COMPAT)
#undef DT_DRV_COMPAT
#define DT_DRV_COMPAT xlnx_xps_iic_2_00_a
DT_INST_FOREACH_STATUS_OKAY_VARGS(I2C_XILINX_AXI_INIT, DT_DRV_COMPAT)