[PATCH 16/16] drivers/fsi: Add GPIO based FSI master
From: Chris Bostic
Date: Tue Dec 06 2016 - 19:16:14 EST
From: Chris Bostic <cbostic@xxxxxxxxxx>
Implement a FSI master using GPIO. Will generate FSI protocol for
read and write commands to particular addresses. Sends master command
and waits for and decodes a slave response.
Includes Jeremy Kerr's original GPIO master base commit.
Signed-off-by: Jeremy Kerr <jk@xxxxxxxxxx>
Signed-off-by: Chris Bostic <cbostic@xxxxxxxxxx>
---
drivers/fsi/Kconfig | 7 +
drivers/fsi/Makefile | 1 +
drivers/fsi/fsi-master-gpio.c | 552 ++++++++++++++++++++++++++++++++++++++++++
3 files changed, 560 insertions(+)
create mode 100644 drivers/fsi/fsi-master-gpio.c
diff --git a/drivers/fsi/Kconfig b/drivers/fsi/Kconfig
index f065dbe..9530459 100644
--- a/drivers/fsi/Kconfig
+++ b/drivers/fsi/Kconfig
@@ -17,6 +17,13 @@ config FSI_MASTER_FAKE
depends on FSI
---help---
This option enables a fake FSI master driver for debugging.
+
+config FSI_MASTER_GPIO
+ tristate "GPIO-based FSI master"
+ depends on FSI && GPIOLIB
+ ---help---
+ This option enables a FSI master driver using GPIO lines.
+
endif
endmenu
diff --git a/drivers/fsi/Makefile b/drivers/fsi/Makefile
index 847c00c..2021ce5 100644
--- a/drivers/fsi/Makefile
+++ b/drivers/fsi/Makefile
@@ -1,3 +1,4 @@
obj-$(CONFIG_FSI) += fsi-core.o
obj-$(CONFIG_FSI_MASTER_FAKE) += fsi-master-fake.o
+obj-$(CONFIG_FSI_MASTER_GPIO) += fsi-master-gpio.o
diff --git a/drivers/fsi/fsi-master-gpio.c b/drivers/fsi/fsi-master-gpio.c
new file mode 100644
index 0000000..79cb0b1
--- /dev/null
+++ b/drivers/fsi/fsi-master-gpio.c
@@ -0,0 +1,552 @@
+/*
+ * A FSI master controller, using a simple GPIO bit-banging interface
+ */
+
+#include <linux/platform_device.h>
+#include <linux/gpio/consumer.h>
+#include <linux/module.h>
+#include <linux/delay.h>
+#include <linux/fsi.h>
+#include <linux/device.h>
+#include <linux/io.h>
+#include <linux/spinlock.h>
+
+#include "fsi-master.h"
+
+#define FSI_GPIO_STD_DLY 1 /* Standard pin delay in nS */
+#define FSI_ECHO_DELAY_CLOCKS 16 /* Number clocks for echo delay */
+#define FSI_PRE_BREAK_CLOCKS 50 /* Number clocks to prep for break */
+#define FSI_BREAK_CLOCKS 256 /* Number of clocks to issue break */
+#define FSI_POST_BREAK_CLOCKS 16000 /* Number clocks to set up cfam */
+#define FSI_INIT_CLOCKS 5000 /* Clock out any old data */
+#define FSI_GPIO_STD_DELAY 10 /* Standard GPIO delay in nS */
+ /* todo: adjust down as low as */
+ /* possible or eliminate */
+#define FSI_GPIO_CMD_DPOLL 0x000000000000002AULL
+#define FSI_GPIO_CMD_DPOLL_SIZE 9
+#define FSI_GPIO_DPOLL_CLOCKS 100 /* < 21 will cause slave to hang */
+#define FSI_GPIO_CMD_DEFAULT 0x2000000000000000ULL
+#define FSI_GPIO_CMD_WRITE 0
+#define FSI_GPIO_CMD_READ 0x0400000000000000ULL
+#define FSI_GPIO_CMD_SLAVE_MASK 0xC000000000000000ULL
+#define FSI_GPIO_CMD_ADDR_SHIFT 37
+#define FSI_GPIO_CMD_ADDR_MASK 0x001FFFFF
+#define FSI_GPIO_CMD_SLV_SHIFT 62
+#define FSI_GPIO_CMD_SIZE_16 0x0000001000000000ULL
+#define FSI_GPIO_CMD_SIZE_32 0x0000003000000000ULL
+#define FSI_GPIO_CMD_DT32_SHIFT 4
+#define FSI_GPIO_CMD_DT16_SHIFT 20
+#define FSI_GPIO_CMD_DT8_SHIFT 28
+#define FSI_GPIO_CMD_DFLT_LEN 28
+#define FSI_GPIO_CMD_CRC_SHIFT 60
+
+/* Bus errors */
+#define FSI_GPIO_ERR_BUSY 1 /* Slave stuck in busy state */
+#define FSI_GPIO_RESP_ERRA 2 /* Any (misc) Error */
+#define FSI_GPIO_RESP_ERRC 3 /* Slave reports master CRC error */
+#define FSI_GPIO_MTOE 4 /* Master time out error */
+#define FSI_GPIO_CRC_INVAL 5 /* Master reports slave CRC error */
+
+/* Normal slave responses */
+#define FSI_GPIO_RESP_BUSY 1
+#define FSI_GPIO_RESP_ACK 0
+#define FSI_GPIO_RESP_ACKD 4
+
+#define FSI_GPIO_MAX_BUSY 100
+#define FSI_GPIO_MTOE_COUNT 1000
+#define FSI_GPIO_DRAIN_BITS 20
+#define FSI_GPIO_CRC_SIZE 4
+#define FSI_GPIO_MSG_ID_SIZE 2
+#define FSI_GPIO_MSG_RESPID_SIZE 2
+#define FSI_GPIO_PRIME_SLAVE_CLOCKS 100
+
+static DEFINE_SPINLOCK(fsi_gpio_cmd_lock); /* lock around fsi commands */
+
+struct fsi_master_gpio {
+ struct fsi_master master;
+ struct gpio_desc *gpio_clk;
+ struct gpio_desc *gpio_data;
+ struct gpio_desc *gpio_trans; /* Voltage translator */
+ struct gpio_desc *gpio_enable; /* FSI enable */
+ struct gpio_desc *gpio_mux; /* Mux control */
+};
+
+#define to_fsi_master_gpio(m) container_of(m, struct fsi_master_gpio, master)
+
+struct fsi_gpio_msg {
+ uint64_t msg;
+ uint8_t bits;
+};
+
+static void clock_toggle(struct fsi_master_gpio *master, int count)
+{
+ int i;
+
+ for (i = 0; i < count; i++) {
+ ndelay(FSI_GPIO_STD_DLY);
+ gpiod_set_value(master->gpio_clk, 0);
+ ndelay(FSI_GPIO_STD_DLY);
+ gpiod_set_value(master->gpio_clk, 1);
+ }
+}
+
+static int sda_in(struct fsi_master_gpio *master)
+{
+ int in;
+
+ ndelay(FSI_GPIO_STD_DLY);
+ in = gpiod_get_value(master->gpio_data);
+ return in ? 1 : 0;
+}
+
+static void sda_out(struct fsi_master_gpio *master, int value)
+{
+ gpiod_set_value(master->gpio_data, value);
+}
+
+static void set_sda_input(struct fsi_master_gpio *master)
+{
+ gpiod_direction_input(master->gpio_data);
+ if (master->gpio_trans)
+ gpiod_set_value(master->gpio_trans, 0);
+}
+
+static void set_sda_output(struct fsi_master_gpio *master, int value)
+{
+ if (master->gpio_trans)
+ gpiod_set_value(master->gpio_trans, 1);
+ gpiod_direction_output(master->gpio_data, value);
+}
+
+static void serial_in(struct fsi_master_gpio *master, struct fsi_gpio_msg *cmd,
+ uint8_t num_bits)
+{
+ uint8_t bit;
+ uint64_t msg = 0;
+ uint8_t in_bit = 0;
+
+ set_sda_input(master);
+
+ for (bit = 0; bit < num_bits; bit++) {
+ clock_toggle(master, 1);
+ in_bit = sda_in(master);
+ msg <<= 1;
+ msg |= ~in_bit & 0x1; /* Data is negative active */
+ }
+ cmd->bits = num_bits;
+ cmd->msg = msg;
+}
+
+static void serial_out(struct fsi_master_gpio *master,
+ const struct fsi_gpio_msg *cmd)
+{
+ uint8_t bit;
+ uint64_t msg = ~cmd->msg; /* Data is negative active */
+ uint64_t sda_mask = 0x1ULL << (cmd->bits - 1);
+ uint64_t last_bit = ~0;
+ int next_bit;
+
+ if (!cmd->bits) {
+ dev_warn(master->master.dev, "trying to output 0 bits\n");
+ return;
+ }
+ set_sda_output(master, 0);
+
+ /* Send the start bit */
+ sda_out(master, 0);
+ clock_toggle(master, 1);
+
+ /* Send the message */
+ for (bit = 0; bit < cmd->bits; bit++) {
+ next_bit = (msg & sda_mask) >> (cmd->bits - 1);
+ if (last_bit ^ next_bit) {
+ sda_out(master, next_bit);
+ last_bit = next_bit;
+ }
+ clock_toggle(master, 1);
+ msg <<= 1;
+ }
+}
+
+/*
+ * Clock out some 0's after every message to ride out line reflections
+ */
+static void echo_delay(struct fsi_master_gpio *master)
+{
+ set_sda_output(master, 1);
+ clock_toggle(master, FSI_ECHO_DELAY_CLOCKS);
+}
+
+/*
+ * Used in bus error cases only. Clears out any remaining data the slave
+ * is attempting to send
+ */
+static void drain_response(struct fsi_master_gpio *master)
+{
+ struct fsi_gpio_msg msg;
+
+ serial_in(master, &msg, FSI_GPIO_DRAIN_BITS);
+}
+
+/*
+ * Store information on master errors so handler can detect and clean
+ * up the bus
+ */
+static void fsi_master_gpio_error(struct fsi_master_gpio *master, int error)
+{
+
+}
+
+static int poll_for_response(struct fsi_master_gpio *master, uint8_t expected,
+ uint8_t size, void *data)
+{
+ int busy_count = 0, i;
+ struct fsi_gpio_msg response, cmd;
+ int bits_remaining = 0, bit_count, response_id, id;
+ uint64_t resp = 0;
+ uint8_t bits_received = FSI_GPIO_MSG_ID_SIZE +
+ FSI_GPIO_MSG_RESPID_SIZE;
+ uint8_t crc_in;
+
+ do {
+ for (i = 0; i < FSI_GPIO_MTOE_COUNT; i++) {
+ serial_in(master, &response, 1);
+ if (response.msg)
+ break;
+ }
+ if (i >= FSI_GPIO_MTOE_COUNT) {
+ dev_dbg(master->master.dev,
+ "Master time out waiting for response\n");
+ drain_response(master);
+ fsi_master_gpio_error(master, FSI_GPIO_MTOE);
+ return -EIO;
+ }
+
+ /* Response received */
+ bit_count = FSI_GPIO_MSG_ID_SIZE + FSI_GPIO_MSG_RESPID_SIZE;
+ serial_in(master, &response, bit_count);
+
+ response_id = response.msg & 0x3;
+ id = (response.msg >> FSI_GPIO_MSG_RESPID_SIZE) & 0x3;
+ dev_dbg(master->master.dev, "id:%d resp:%d\n", id, response_id);
+
+ resp = response.msg;
+
+ switch (response_id) {
+ case FSI_GPIO_RESP_ACK:
+ if (expected == FSI_GPIO_RESP_ACKD)
+ bits_remaining = 8 * size;
+ break;
+
+ case FSI_GPIO_RESP_BUSY:
+ /*
+ * Its necessary to clock slave before issuing
+ * d-poll, not indicated in the hardware protocol
+ * spec. < 20 clocks causes slave to hang, 21 ok.
+ */
+ set_sda_output(master, 1);
+ clock_toggle(master, FSI_GPIO_DPOLL_CLOCKS);
+ cmd.msg = FSI_GPIO_CMD_DPOLL;
+ cmd.bits = FSI_GPIO_CMD_DPOLL_SIZE;
+ serial_out(master, &cmd);
+ echo_delay(master);
+ continue;
+
+ case FSI_GPIO_RESP_ERRA:
+ case FSI_GPIO_RESP_ERRC:
+ dev_dbg(master->master.dev, "ERR received: %d\n",
+ (int)response.msg);
+ /*
+ * todo: Verify crc from slave and in general
+ * only act on any response if crc is correct
+ */
+ clock_toggle(master, FSI_GPIO_CRC_SIZE);
+ fsi_master_gpio_error(master, response.msg);
+ return -EIO;
+ }
+
+ /* Read in the data field if applicable */
+ if (bits_remaining) {
+ serial_in(master, &response, bits_remaining);
+ resp <<= bits_remaining;
+ resp |= response.msg;
+ bits_received += bits_remaining;
+ *((uint32_t *)data) = response.msg;
+ }
+
+ crc_in = fsi_crc4(0, resp | (0x1ULL << bits_received),
+ bits_received + 1);
+
+ /* Read in the crc and check it */
+ serial_in(master, &response, FSI_GPIO_CRC_SIZE);
+ if (crc_in != response.msg) {
+ dev_dbg(master->master.dev, "ERR response CRC\n");
+ fsi_master_gpio_error(master, FSI_GPIO_CRC_INVAL);
+ return -EIO;
+ }
+ /* Clock the slave enough to be ready for next operation */
+ clock_toggle(master, FSI_GPIO_PRIME_SLAVE_CLOCKS);
+ return 0;
+
+ } while (busy_count++ < FSI_GPIO_MAX_BUSY);
+
+ dev_dbg(master->master.dev, "ERR slave is stuck in busy state\n");
+ fsi_master_gpio_error(master, FSI_GPIO_ERR_BUSY);
+
+ return -EIO;
+}
+
+static void build_abs_ar_command(struct fsi_gpio_msg *cmd, uint64_t mode,
+ uint8_t slave, uint32_t addr, size_t size,
+ const void *data)
+{
+ uint8_t crc;
+
+ cmd->bits = FSI_GPIO_CMD_DFLT_LEN;
+ cmd->msg = FSI_GPIO_CMD_DEFAULT;
+ cmd->msg |= mode;
+ cmd->msg &= ~FSI_GPIO_CMD_SLAVE_MASK;
+ cmd->msg |= (((uint64_t)slave) << FSI_GPIO_CMD_SLV_SHIFT);
+ addr &= FSI_GPIO_CMD_ADDR_MASK;
+ cmd->msg |= (((uint64_t)addr) << FSI_GPIO_CMD_ADDR_SHIFT);
+ if (size == sizeof(uint8_t)) {
+ if (data) {
+ uint8_t cmd_data = *((uint8_t *)data);
+
+ cmd->msg |=
+ ((uint64_t)cmd_data) << FSI_GPIO_CMD_DT8_SHIFT;
+ }
+ } else if (size == sizeof(uint16_t)) {
+ cmd->msg |= FSI_GPIO_CMD_SIZE_16;
+ if (data) {
+ uint16_t cmd_data;
+
+ memcpy(&cmd_data, data, size);
+ cmd->msg |=
+ ((uint64_t)cmd_data) << FSI_GPIO_CMD_DT16_SHIFT;
+ }
+ } else {
+ cmd->msg |= FSI_GPIO_CMD_SIZE_32;
+ if (data) {
+ uint32_t cmd_data;
+
+ memcpy(&cmd_data, data, size);
+ cmd->msg |=
+ ((uint64_t)cmd_data) << FSI_GPIO_CMD_DT32_SHIFT;
+ }
+ }
+
+ if (mode == FSI_GPIO_CMD_WRITE)
+ cmd->bits += (8 * size);
+
+ /* Include start bit */
+ crc = fsi_crc4(0,
+ (cmd->msg >> (64 - cmd->bits)) | (0x1ULL << cmd->bits),
+ cmd->bits + 1);
+ cmd->msg |= ((uint64_t)crc) << (FSI_GPIO_CMD_CRC_SHIFT - cmd->bits);
+ cmd->bits += FSI_GPIO_CRC_SIZE;
+
+ /* Right align message */
+ cmd->msg >>= (64 - cmd->bits);
+}
+
+static int fsi_master_gpio_read(struct fsi_master *_master, int link,
+ uint8_t slave, uint32_t addr, void *val, size_t size)
+{
+ struct fsi_master_gpio *master = to_fsi_master_gpio(_master);
+ struct fsi_gpio_msg cmd;
+ int rc;
+ unsigned long flags;
+
+ if (link != 0)
+ return -ENODEV;
+
+ build_abs_ar_command(&cmd, FSI_GPIO_CMD_READ, slave, addr, size, NULL);
+
+ spin_lock_irqsave(&fsi_gpio_cmd_lock, flags);
+ serial_out(master, &cmd);
+ echo_delay(master);
+ rc = poll_for_response(master, FSI_GPIO_RESP_ACKD, size, val);
+ spin_unlock_irqrestore(&fsi_gpio_cmd_lock, flags);
+
+ return rc;
+}
+
+static int fsi_master_gpio_write(struct fsi_master *_master, int link,
+ uint8_t slave, uint32_t addr, const void *val, size_t size)
+{
+ struct fsi_master_gpio *master = to_fsi_master_gpio(_master);
+ struct fsi_gpio_msg cmd;
+ int rc;
+ unsigned long flags;
+
+ if (link != 0)
+ return -ENODEV;
+
+ build_abs_ar_command(&cmd, FSI_GPIO_CMD_WRITE, slave, addr, size, val);
+
+ spin_lock_irqsave(&fsi_gpio_cmd_lock, flags);
+ serial_out(master, &cmd);
+ echo_delay(master);
+ rc = poll_for_response(master, FSI_GPIO_RESP_ACK, size, NULL);
+ spin_unlock_irqrestore(&fsi_gpio_cmd_lock, flags);
+
+ return rc;
+}
+
+/*
+ * Issue a break command on link
+ */
+static int fsi_master_gpio_break(struct fsi_master *_master, int link)
+{
+ struct fsi_master_gpio *master = to_fsi_master_gpio(_master);
+
+ if (link != 0)
+ return -ENODEV;
+
+ set_sda_output(master, 1);
+ clock_toggle(master, FSI_PRE_BREAK_CLOCKS);
+ sda_out(master, 0);
+ clock_toggle(master, FSI_BREAK_CLOCKS);
+ echo_delay(master);
+ sda_out(master, 1);
+ clock_toggle(master, FSI_POST_BREAK_CLOCKS);
+
+ /* Wait for logic reset to take effect */
+ udelay(200);
+
+ return 0;
+}
+
+static void fsi_master_gpio_init(struct fsi_master_gpio *master)
+{
+ if (master->gpio_mux)
+ gpiod_direction_output(master->gpio_mux, 1);
+ if (master->gpio_trans)
+ gpiod_direction_output(master->gpio_trans, 1);
+ if (master->gpio_enable)
+ gpiod_direction_output(master->gpio_enable, 1);
+ gpiod_direction_output(master->gpio_clk, 1);
+ gpiod_direction_output(master->gpio_data, 1);
+
+ /* todo: evaluate if clocks can be reduced */
+ clock_toggle(master, FSI_INIT_CLOCKS);
+}
+
+static int fsi_master_gpio_link_enable(struct fsi_master *_master, int link)
+{
+ struct fsi_master_gpio *master = to_fsi_master_gpio(_master);
+
+ if (link != 0)
+ return -ENODEV;
+ if (master->gpio_enable)
+ gpiod_set_value(master->gpio_enable, 1);
+
+ return 0;
+}
+
+static ssize_t store_scan(struct device *dev,
+ struct device_attribute *attr,
+ const char *buf,
+ size_t count)
+{
+ struct fsi_master_gpio *master = dev_get_drvdata(dev);
+
+ fsi_master_gpio_init(master);
+
+ /* clear out any old scan data if present */
+ fsi_master_unregister(&master->master);
+ fsi_master_register(&master->master);
+
+ return count;
+}
+
+static DEVICE_ATTR(scan, 0200, NULL, store_scan);
+
+static int fsi_master_gpio_probe(struct platform_device *pdev)
+{
+ struct fsi_master_gpio *master;
+ struct gpio_desc *gpio;
+
+ master = devm_kzalloc(&pdev->dev, sizeof(*master), GFP_KERNEL);
+ if (!master)
+ return -ENOMEM;
+
+ gpio = devm_gpiod_get(&pdev->dev, "clock", 0);
+ if (IS_ERR(gpio)) {
+ dev_dbg(&pdev->dev, "probe: failed to get clock pin\n");
+ return PTR_ERR(gpio);
+ }
+ master->gpio_clk = gpio;
+
+ gpio = devm_gpiod_get(&pdev->dev, "data", 0);
+ if (IS_ERR(gpio)) {
+ dev_dbg(&pdev->dev, "probe: failed to get data pin\n");
+ return PTR_ERR(gpio);
+ }
+ master->gpio_data = gpio;
+
+ /* Optional pins */
+
+ gpio = devm_gpiod_get(&pdev->dev, "trans", 0);
+ if (IS_ERR(gpio))
+ dev_dbg(&pdev->dev, "probe: failed to get trans pin\n");
+ else
+ master->gpio_trans = gpio;
+
+ gpio = devm_gpiod_get(&pdev->dev, "enable", 0);
+ if (IS_ERR(gpio))
+ dev_dbg(&pdev->dev, "probe: failed to get enable pin\n");
+ else
+ master->gpio_enable = gpio;
+
+ gpio = devm_gpiod_get(&pdev->dev, "mux", 0);
+ if (IS_ERR(gpio))
+ dev_dbg(&pdev->dev, "probe: failed to get mux pin\n");
+ else
+ master->gpio_mux = gpio;
+
+ master->master.n_links = 1;
+ master->master.read = fsi_master_gpio_read;
+ master->master.write = fsi_master_gpio_write;
+ master->master.send_break = fsi_master_gpio_break;
+ master->master.link_enable = fsi_master_gpio_link_enable;
+ platform_set_drvdata(pdev, master);
+
+ return device_create_file(&pdev->dev, &dev_attr_scan);
+}
+
+
+static int fsi_master_gpio_remove(struct platform_device *pdev)
+{
+ struct fsi_master_gpio *master = platform_get_drvdata(pdev);
+
+ devm_gpiod_put(&pdev->dev, master->gpio_clk);
+ devm_gpiod_put(&pdev->dev, master->gpio_data);
+ if (master->gpio_trans)
+ devm_gpiod_put(&pdev->dev, master->gpio_trans);
+ if (master->gpio_enable)
+ devm_gpiod_put(&pdev->dev, master->gpio_enable);
+ if (master->gpio_mux)
+ devm_gpiod_put(&pdev->dev, master->gpio_mux);
+ fsi_master_unregister(&master->master);
+
+ return 0;
+}
+
+static const struct of_device_id fsi_master_gpio_match[] = {
+ { .compatible = "ibm,fsi-master-gpio" },
+ { },
+};
+
+static struct platform_driver fsi_master_gpio_driver = {
+ .driver = {
+ .name = "fsi-master-gpio",
+ .of_match_table = fsi_master_gpio_match,
+ },
+ .probe = fsi_master_gpio_probe,
+ .remove = fsi_master_gpio_remove,
+};
+
+module_platform_driver(fsi_master_gpio_driver);
+MODULE_LICENSE("GPL");
--
1.8.2.2