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Subject[PATCH v6 19/23] drivers/fsi: Add GPIO based FSI master
Date
From: Chris Bostic <cbostic@linux.vnet.ibm.com>

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 changes from Edward A. James <eajames@us.ibm.com> and Jeremy
Kerr <jk@ozlabs.org>.

Signed-off-by: Edward A. James <eajames@us.ibm.com>
Signed-off-by: Jeremy Kerr <jk@ozlabs.org>
Signed-off-by: Chris Bostic <cbostic@linux.vnet.ibm.com>
Signed-off-by: Joel Stanley <joel@jms.id.au>
---
drivers/fsi/Kconfig | 11 +
drivers/fsi/Makefile | 1 +
drivers/fsi/fsi-master-gpio.c | 610 ++++++++++++++++++++++++++++++++++++++++++
3 files changed, 622 insertions(+)
create mode 100644 drivers/fsi/fsi-master-gpio.c

diff --git a/drivers/fsi/Kconfig b/drivers/fsi/Kconfig
index 04c1a0e..448bc3b 100644
--- a/drivers/fsi/Kconfig
+++ b/drivers/fsi/Kconfig
@@ -9,4 +9,15 @@ config FSI
---help---
FSI - the FRU Support Interface - is a simple bus for low-level
access to POWER-based hardware.
+
+if FSI
+
+config FSI_MASTER_GPIO
+ tristate "GPIO-based FSI master"
+ depends on 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 db0e5e7..ed28ac0 100644
--- a/drivers/fsi/Makefile
+++ b/drivers/fsi/Makefile
@@ -1,2 +1,3 @@

obj-$(CONFIG_FSI) += fsi-core.o
+obj-$(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..9fedfaf
--- /dev/null
+++ b/drivers/fsi/fsi-master-gpio.c
@@ -0,0 +1,610 @@
+/*
+ * 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/slab.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 0x2
+#define FSI_GPIO_CMD_TERM 0x3f
+#define FSI_GPIO_CMD_ABS_AR 0x4
+
+#define FSI_GPIO_DPOLL_CLOCKS 100 /* < 21 will cause slave to hang */
+
+/* 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 device *dev;
+ 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 clock_zeros(struct fsi_master_gpio *master, int count)
+{
+ set_sda_output(master, 1);
+ clock_toggle(master, count);
+}
+
+static void serial_in(struct fsi_master_gpio *master, struct fsi_gpio_msg *msg,
+ uint8_t num_bits)
+{
+ uint8_t bit, in_bit;
+
+ set_sda_input(master);
+
+ for (bit = 0; bit < num_bits; bit++) {
+ clock_toggle(master, 1);
+ in_bit = sda_in(master);
+ msg->msg <<= 1;
+ msg->msg |= ~in_bit & 0x1; /* Data is negative active */
+ }
+ msg->bits += num_bits;
+}
+
+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->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;
+ }
+}
+
+static void msg_push_bits(struct fsi_gpio_msg *msg, uint64_t data, int bits)
+{
+ msg->msg <<= bits;
+ msg->msg |= data & ((1ull << bits) - 1);
+ msg->bits += bits;
+}
+
+static void msg_push_crc(struct fsi_gpio_msg *msg)
+{
+ uint8_t crc;
+ int top;
+
+ top = msg->bits & 0x3;
+
+ /* start bit, and any non-aligned top bits */
+ crc = fsi_crc4(0,
+ 1 << top | msg->msg >> (msg->bits - top),
+ top + 1);
+
+ /* aligned bits */
+ crc = fsi_crc4(crc, msg->msg, msg->bits - top);
+
+ msg_push_bits(msg, crc, 4);
+}
+
+static void build_abs_ar_command(struct fsi_gpio_msg *cmd,
+ uint8_t id, uint32_t addr, size_t size, const void *data)
+{
+ bool write = !!data;
+ uint8_t ds;
+ int i;
+
+ cmd->bits = 0;
+ cmd->msg = 0;
+
+ msg_push_bits(cmd, id, 2);
+ msg_push_bits(cmd, FSI_GPIO_CMD_ABS_AR, 3);
+ msg_push_bits(cmd, write ? 0 : 1, 1);
+
+ /*
+ * The read/write size is encoded in the lower bits of the address
+ * (as it must be naturally-aligned), and the following ds bit.
+ *
+ * size addr:1 addr:0 ds
+ * 1 x x 0
+ * 2 x 0 1
+ * 4 0 1 1
+ *
+ */
+ ds = size > 1 ? 1 : 0;
+ addr &= ~(size - 1);
+ if (size == 4)
+ addr |= 1;
+
+ msg_push_bits(cmd, addr & ((1 << 21) - 1), 21);
+ msg_push_bits(cmd, ds, 1);
+ for (i = 0; write && i < size; i++)
+ msg_push_bits(cmd, ((uint8_t *)data)[i], 8);
+
+ msg_push_crc(cmd);
+}
+
+static void build_dpoll_command(struct fsi_gpio_msg *cmd, uint8_t slave_id)
+{
+ cmd->bits = 0;
+ cmd->msg = 0;
+
+ msg_push_bits(cmd, slave_id, 2);
+ msg_push_bits(cmd, FSI_GPIO_CMD_DPOLL, 3);
+ msg_push_crc(cmd);
+}
+
+static void echo_delay(struct fsi_master_gpio *master)
+{
+ set_sda_output(master, 1);
+ clock_toggle(master, FSI_ECHO_DELAY_CLOCKS);
+}
+
+static void build_term_command(struct fsi_gpio_msg *cmd, uint8_t slave_id)
+{
+ cmd->bits = 0;
+ cmd->msg = 0;
+
+ msg_push_bits(cmd, slave_id, 2);
+ msg_push_bits(cmd, FSI_GPIO_CMD_TERM, 6);
+ msg_push_crc(cmd);
+}
+
+/*
+ * 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 read_one_response(struct fsi_master_gpio *master,
+ uint8_t data_size, struct fsi_gpio_msg *msgp, uint8_t *tagp)
+{
+ struct fsi_gpio_msg msg;
+ uint8_t id, tag;
+ uint32_t crc;
+ int i;
+
+ /* wait for the start bit */
+ for (i = 0; i < FSI_GPIO_MTOE_COUNT; i++) {
+ msg.bits = 0;
+ msg.msg = 0;
+ serial_in(master, &msg, 1);
+ if (msg.msg)
+ break;
+ }
+ if (i >= FSI_GPIO_MTOE_COUNT) {
+ dev_dbg(master->dev,
+ "Master time out waiting for response\n");
+ fsi_master_gpio_error(master, FSI_GPIO_MTOE);
+ return -EIO;
+ }
+
+ msg.bits = 0;
+ msg.msg = 0;
+
+ /* Read slave ID & response tag */
+ serial_in(master, &msg, 4);
+
+ id = (msg.msg >> FSI_GPIO_MSG_RESPID_SIZE) & 0x3;
+ tag = msg.msg & 0x3;
+
+ /* if we have an ACK, and we're expecting data, clock the
+ * data in too
+ */
+ if (tag == FSI_GPIO_RESP_ACK && data_size)
+ serial_in(master, &msg, data_size * 8);
+
+ /* read CRC */
+ serial_in(master, &msg, FSI_GPIO_CRC_SIZE);
+
+ /* we have a whole message now; check CRC */
+ crc = fsi_crc4(0, 1, 1);
+ crc = fsi_crc4(crc, msg.msg, msg.bits);
+ if (crc) {
+ dev_dbg(master->dev, "ERR response CRC\n");
+ fsi_master_gpio_error(master, FSI_GPIO_CRC_INVAL);
+ return -EIO;
+ }
+
+ if (msgp)
+ *msgp = msg;
+ if (tagp)
+ *tagp = tag;
+
+ return 0;
+}
+
+static int issue_term(struct fsi_master_gpio *master, uint8_t slave)
+{
+ struct fsi_gpio_msg cmd;
+ uint8_t tag;
+ int rc;
+
+ build_term_command(&cmd, slave);
+ serial_out(master, &cmd);
+ echo_delay(master);
+
+ rc = read_one_response(master, 0, NULL, &tag);
+ if (rc) {
+ dev_err(master->dev,
+ "TERM failed; lost communication with slave\n");
+ return -EIO;
+ } else if (tag != FSI_GPIO_RESP_ACK) {
+ dev_err(master->dev, "TERM failed; response %d\n", tag);
+ return -EIO;
+ }
+
+ return 0;
+}
+
+static int poll_for_response(struct fsi_master_gpio *master,
+ uint8_t slave, uint8_t size, void *data)
+{
+ struct fsi_gpio_msg response, cmd;
+ int busy_count = 0, rc, i;
+ uint8_t tag;
+
+retry:
+ rc = read_one_response(master, size, &response, &tag);
+ if (rc)
+ return rc;
+
+ switch (tag) {
+ case FSI_GPIO_RESP_ACK:
+ if (size && data) {
+ uint64_t val = response.msg;
+ /* clear crc & mask */
+ val >>= 4;
+ val &= (1ull << (size * 8)) - 1;
+
+ for (i = 0; i < size; i++) {
+ ((uint8_t *)data)[size-i-1] =
+ val & 0xff;
+ val >>= 8;
+ }
+ }
+ 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.
+ */
+ clock_zeros(master, FSI_GPIO_DPOLL_CLOCKS);
+ if (busy_count++ < FSI_GPIO_MAX_BUSY) {
+ build_dpoll_command(&cmd, slave);
+ serial_out(master, &cmd);
+ echo_delay(master);
+ goto retry;
+ }
+ dev_warn(master->dev,
+ "ERR slave is stuck in busy state, issuing TERM\n");
+ issue_term(master, slave);
+ rc = -EIO;
+ break;
+
+ case FSI_GPIO_RESP_ERRA:
+ case FSI_GPIO_RESP_ERRC:
+ dev_dbg(master->dev, "ERR%c received: 0x%x\n",
+ tag == FSI_GPIO_RESP_ERRA ? 'A' : 'C',
+ (int)response.msg);
+ fsi_master_gpio_error(master, response.msg);
+ rc = -EIO;
+ break;
+ }
+
+ /* Clock the slave enough to be ready for next operation */
+ clock_zeros(master, FSI_GPIO_PRIME_SLAVE_CLOCKS);
+ return rc;
+}
+
+static int fsi_master_gpio_xfer(struct fsi_master_gpio *master, uint8_t slave,
+ struct fsi_gpio_msg *cmd, size_t resp_len, void *resp)
+{
+ unsigned long flags;
+ int rc;
+
+ spin_lock_irqsave(&fsi_gpio_cmd_lock, flags);
+ serial_out(master, cmd);
+ echo_delay(master);
+ rc = poll_for_response(master, slave, resp_len, resp);
+ spin_unlock_irqrestore(&fsi_gpio_cmd_lock, flags);
+
+ return rc;
+}
+
+static int fsi_master_gpio_read(struct fsi_master *_master, int link,
+ uint8_t id, uint32_t addr, void *val, size_t size)
+{
+ struct fsi_master_gpio *master = to_fsi_master_gpio(_master);
+ struct fsi_gpio_msg cmd;
+
+ if (link != 0)
+ return -ENODEV;
+
+ build_abs_ar_command(&cmd, id, addr, size, NULL);
+ return fsi_master_gpio_xfer(master, id, &cmd, size, val);
+}
+
+static int fsi_master_gpio_write(struct fsi_master *_master, int link,
+ uint8_t id, uint32_t addr, const void *val, size_t size)
+{
+ struct fsi_master_gpio *master = to_fsi_master_gpio(_master);
+ struct fsi_gpio_msg cmd;
+
+ if (link != 0)
+ return -ENODEV;
+
+ build_abs_ar_command(&cmd, id, addr, size, val);
+ return fsi_master_gpio_xfer(master, id, &cmd, 0, NULL);
+}
+
+static int fsi_master_gpio_term(struct fsi_master *_master,
+ int link, uint8_t id)
+{
+ struct fsi_master_gpio *master = to_fsi_master_gpio(_master);
+ struct fsi_gpio_msg cmd;
+
+ if (link != 0)
+ return -ENODEV;
+
+ build_term_command(&cmd, id);
+ return fsi_master_gpio_xfer(master, id, &cmd, 0, NULL);
+}
+
+/*
+ * 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);
+ sda_out(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_zeros(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 void fsi_master_gpio_release(struct device *dev)
+{
+}
+
+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;
+
+ master->dev = &pdev->dev;
+ master->master.dev.parent = master->dev;
+ master->master.dev.release = fsi_master_gpio_release;
+
+ gpio = devm_gpiod_get(&pdev->dev, "clock", 0);
+ if (IS_ERR(gpio)) {
+ dev_err(&pdev->dev, "failed to get clock gpio\n");
+ return PTR_ERR(gpio);
+ }
+ master->gpio_clk = gpio;
+
+ gpio = devm_gpiod_get(&pdev->dev, "data", 0);
+ if (IS_ERR(gpio)) {
+ dev_err(&pdev->dev, "failed to get data gpio\n");
+ return PTR_ERR(gpio);
+ }
+ master->gpio_data = gpio;
+
+ /* Optional GPIOs */
+ gpio = devm_gpiod_get_optional(&pdev->dev, "trans", 0);
+ if (IS_ERR(gpio)) {
+ dev_err(&pdev->dev, "failed to get trans gpio\n");
+ return PTR_ERR(gpio);
+ }
+ master->gpio_trans = gpio;
+
+ gpio = devm_gpiod_get_optional(&pdev->dev, "enable", 0);
+ if (IS_ERR(gpio)) {
+ dev_err(&pdev->dev, "failed to get enable gpio\n");
+ return PTR_ERR(gpio);
+ }
+ master->gpio_enable = gpio;
+
+ gpio = devm_gpiod_get_optional(&pdev->dev, "mux", 0);
+ if (IS_ERR(gpio)) {
+ dev_err(&pdev->dev, "failed to get mux gpio\n");
+ return PTR_ERR(gpio);
+ }
+ 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.term = fsi_master_gpio_term;
+ master->master.send_break = fsi_master_gpio_break;
+ master->master.link_enable = fsi_master_gpio_link_enable;
+ platform_set_drvdata(pdev, master);
+
+ fsi_master_gpio_init(master);
+
+ fsi_master_register(&master->master);
+
+ return 0;
+}
+
+
+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 = "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
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