2 * A FSI master controller, using a simple GPIO bit-banging interface
5 #include <linux/crc4.h>
6 #include <linux/delay.h>
7 #include <linux/device.h>
9 #include <linux/gpio/consumer.h>
11 #include <linux/irqflags.h>
12 #include <linux/module.h>
14 #include <linux/platform_device.h>
15 #include <linux/slab.h>
17 #include "fsi-master.h"
19 #define FSI_GPIO_STD_DLY 1 /* Standard pin delay in nS */
20 #define LAST_ADDR_INVALID 0x1
22 struct fsi_master_gpio {
23 struct fsi_master master;
25 struct mutex cmd_lock; /* mutex for command ordering */
26 struct gpio_desc *gpio_clk;
27 struct gpio_desc *gpio_data;
28 struct gpio_desc *gpio_trans; /* Voltage translator */
29 struct gpio_desc *gpio_enable; /* FSI enable */
30 struct gpio_desc *gpio_mux; /* Mux control */
38 #define CREATE_TRACE_POINTS
39 #include <trace/events/fsi_master_gpio.h>
41 #define to_fsi_master_gpio(m) container_of(m, struct fsi_master_gpio, master)
48 static void clock_toggle(struct fsi_master_gpio *master, int count)
52 for (i = 0; i < count; i++) {
53 if (!master->no_delays)
54 ndelay(FSI_GPIO_STD_DLY);
55 gpiod_set_value(master->gpio_clk, 0);
56 if (!master->no_delays)
57 ndelay(FSI_GPIO_STD_DLY);
58 gpiod_set_value(master->gpio_clk, 1);
62 static int sda_clock_in(struct fsi_master_gpio *master)
66 if (!master->no_delays)
67 ndelay(FSI_GPIO_STD_DLY);
68 gpiod_set_value(master->gpio_clk, 0);
70 /* Dummy read to feed the synchronizers */
71 gpiod_get_value(master->gpio_data);
73 /* Actual data read */
74 in = gpiod_get_value(master->gpio_data);
75 if (!master->no_delays)
76 ndelay(FSI_GPIO_STD_DLY);
77 gpiod_set_value(master->gpio_clk, 1);
81 static void sda_out(struct fsi_master_gpio *master, int value)
83 gpiod_set_value(master->gpio_data, value);
86 static void set_sda_input(struct fsi_master_gpio *master)
88 gpiod_direction_input(master->gpio_data);
89 gpiod_set_value(master->gpio_trans, 0);
92 static void set_sda_output(struct fsi_master_gpio *master, int value)
94 gpiod_set_value(master->gpio_trans, 1);
95 gpiod_direction_output(master->gpio_data, value);
98 static void clock_zeros(struct fsi_master_gpio *master, int count)
100 trace_fsi_master_gpio_clock_zeros(master, count);
101 set_sda_output(master, 1);
102 clock_toggle(master, count);
105 static void echo_delay(struct fsi_master_gpio *master)
107 clock_zeros(master, master->t_echo_delay);
111 static void serial_in(struct fsi_master_gpio *master, struct fsi_gpio_msg *msg,
116 set_sda_input(master);
118 for (bit = 0; bit < num_bits; bit++) {
119 in_bit = sda_clock_in(master);
121 msg->msg |= ~in_bit & 0x1; /* Data is active low */
123 msg->bits += num_bits;
125 trace_fsi_master_gpio_in(master, num_bits, msg->msg);
128 static void serial_out(struct fsi_master_gpio *master,
129 const struct fsi_gpio_msg *cmd)
132 uint64_t msg = ~cmd->msg; /* Data is active low */
133 uint64_t sda_mask = 0x1ULL << (cmd->bits - 1);
134 uint64_t last_bit = ~0;
137 trace_fsi_master_gpio_out(master, cmd->bits, cmd->msg);
140 dev_warn(master->dev, "trying to output 0 bits\n");
143 set_sda_output(master, 0);
145 /* Send the start bit */
147 clock_toggle(master, 1);
149 /* Send the message */
150 for (bit = 0; bit < cmd->bits; bit++) {
151 next_bit = (msg & sda_mask) >> (cmd->bits - 1);
152 if (last_bit ^ next_bit) {
153 sda_out(master, next_bit);
156 clock_toggle(master, 1);
161 static void msg_push_bits(struct fsi_gpio_msg *msg, uint64_t data, int bits)
164 msg->msg |= data & ((1ull << bits) - 1);
168 static void msg_push_crc(struct fsi_gpio_msg *msg)
173 top = msg->bits & 0x3;
175 /* start bit, and any non-aligned top bits */
176 crc = crc4(0, 1 << top | msg->msg >> (msg->bits - top), top + 1);
179 crc = crc4(crc, msg->msg, msg->bits - top);
181 msg_push_bits(msg, crc, 4);
184 static bool check_same_address(struct fsi_master_gpio *master, int id,
187 /* this will also handle LAST_ADDR_INVALID */
188 return master->last_addr == (((id & 0x3) << 21) | (addr & ~0x3));
191 static bool check_relative_address(struct fsi_master_gpio *master, int id,
192 uint32_t addr, uint32_t *rel_addrp)
194 uint32_t last_addr = master->last_addr;
197 if (last_addr == LAST_ADDR_INVALID)
200 /* We may be in 23-bit addressing mode, which uses the id as the
201 * top two address bits. So, if we're referencing a different ID,
202 * use absolute addresses.
204 if (((last_addr >> 21) & 0x3) != id)
207 /* remove the top two bits from any 23-bit addressing */
208 last_addr &= (1 << 21) - 1;
210 /* We know that the addresses are limited to 21 bits, so this won't
211 * overflow the signed rel_addr */
212 rel_addr = addr - last_addr;
213 if (rel_addr > 255 || rel_addr < -256)
216 *rel_addrp = (uint32_t)rel_addr;
221 static void last_address_update(struct fsi_master_gpio *master,
222 int id, bool valid, uint32_t addr)
225 master->last_addr = LAST_ADDR_INVALID;
227 master->last_addr = ((id & 0x3) << 21) | (addr & ~0x3);
231 * Encode an Absolute/Relative/Same Address command
233 static void build_ar_command(struct fsi_master_gpio *master,
234 struct fsi_gpio_msg *cmd, uint8_t id,
235 uint32_t addr, size_t size, const void *data)
237 int i, addr_bits, opcode_bits;
245 /* we have 21 bits of address max */
246 addr &= ((1 << 21) - 1);
248 /* cmd opcodes are variable length - SAME_AR is only two bits */
251 if (check_same_address(master, id, addr)) {
252 /* we still address the byte offset within the word */
255 opcode = FSI_CMD_SAME_AR;
256 trace_fsi_master_gpio_cmd_same_addr(master);
258 } else if (check_relative_address(master, id, addr, &rel_addr)) {
259 /* 8 bits plus sign */
262 opcode = FSI_CMD_REL_AR;
263 trace_fsi_master_gpio_cmd_rel_addr(master, rel_addr);
267 opcode = FSI_CMD_ABS_AR;
268 trace_fsi_master_gpio_cmd_abs_addr(master, addr);
272 * The read/write size is encoded in the lower bits of the address
273 * (as it must be naturally-aligned), and the following ds bit.
275 * size addr:1 addr:0 ds
281 ds = size > 1 ? 1 : 0;
286 msg_push_bits(cmd, id, 2);
287 msg_push_bits(cmd, opcode, opcode_bits);
288 msg_push_bits(cmd, write ? 0 : 1, 1);
289 msg_push_bits(cmd, addr, addr_bits);
290 msg_push_bits(cmd, ds, 1);
291 for (i = 0; write && i < size; i++)
292 msg_push_bits(cmd, ((uint8_t *)data)[i], 8);
297 static void build_dpoll_command(struct fsi_gpio_msg *cmd, uint8_t slave_id)
302 msg_push_bits(cmd, slave_id, 2);
303 msg_push_bits(cmd, FSI_CMD_DPOLL, 3);
307 static void build_epoll_command(struct fsi_gpio_msg *cmd, uint8_t slave_id)
312 msg_push_bits(cmd, slave_id, 2);
313 msg_push_bits(cmd, FSI_CMD_EPOLL, 3);
317 static void build_term_command(struct fsi_gpio_msg *cmd, uint8_t slave_id)
322 msg_push_bits(cmd, slave_id, 2);
323 msg_push_bits(cmd, FSI_CMD_TERM, 6);
328 * Note: callers rely specifically on this returning -EAGAIN for
329 * a CRC error detected in the response. Use other error code
330 * for other situations. It will be converted to something else
331 * higher up the stack before it reaches userspace.
333 static int read_one_response(struct fsi_master_gpio *master,
334 uint8_t data_size, struct fsi_gpio_msg *msgp, uint8_t *tagp)
336 struct fsi_gpio_msg msg;
342 local_irq_save(flags);
344 /* wait for the start bit */
345 for (i = 0; i < FSI_MASTER_MTOE_COUNT; i++) {
348 serial_in(master, &msg, 1);
352 if (i == FSI_MASTER_MTOE_COUNT) {
354 "Master time out waiting for response\n");
355 local_irq_restore(flags);
362 /* Read slave ID & response tag */
363 serial_in(master, &msg, 4);
367 /* If we have an ACK and we're expecting data, clock the data in too */
368 if (tag == FSI_RESP_ACK && data_size)
369 serial_in(master, &msg, data_size * 8);
372 serial_in(master, &msg, FSI_CRC_SIZE);
374 local_irq_restore(flags);
376 /* we have a whole message now; check CRC */
378 crc = crc4(crc, msg.msg, msg.bits);
380 /* Check if it's all 1's, that probably means the host is off */
381 if (((~msg.msg) & ((1ull << msg.bits) - 1)) == 0)
383 dev_dbg(master->dev, "ERR response CRC msg: 0x%016llx (%d bits)\n",
396 static int issue_term(struct fsi_master_gpio *master, uint8_t slave)
398 struct fsi_gpio_msg cmd;
403 build_term_command(&cmd, slave);
405 local_irq_save(flags);
406 serial_out(master, &cmd);
408 local_irq_restore(flags);
410 rc = read_one_response(master, 0, NULL, &tag);
413 "TERM failed; lost communication with slave\n");
415 } else if (tag != FSI_RESP_ACK) {
416 dev_err(master->dev, "TERM failed; response %d\n", tag);
423 static int poll_for_response(struct fsi_master_gpio *master,
424 uint8_t slave, uint8_t size, void *data)
426 struct fsi_gpio_msg response, cmd;
427 int busy_count = 0, rc, i;
430 uint8_t *data_byte = data;
431 int crc_err_retries = 0;
433 rc = read_one_response(master, size, &response, &tag);
435 /* Handle retries on CRC errors */
437 /* Too many retries ? */
438 if (crc_err_retries++ > FSI_CRC_ERR_RETRIES) {
440 * Pass it up as a -EIO otherwise upper level will retry
441 * the whole command which isn't what we want here.
447 "CRC error retry %d\n", crc_err_retries);
448 trace_fsi_master_gpio_crc_rsp_error(master);
449 build_epoll_command(&cmd, slave);
450 local_irq_save(flags);
451 clock_zeros(master, FSI_MASTER_EPOLL_CLOCKS);
452 serial_out(master, &cmd);
454 local_irq_restore(flags);
462 uint64_t val = response.msg;
463 /* clear crc & mask */
465 val &= (1ull << (size * 8)) - 1;
467 for (i = 0; i < size; i++) {
468 data_byte[size-i-1] = val;
475 * Its necessary to clock slave before issuing
476 * d-poll, not indicated in the hardware protocol
477 * spec. < 20 clocks causes slave to hang, 21 ok.
479 if (busy_count++ < FSI_MASTER_MAX_BUSY) {
480 build_dpoll_command(&cmd, slave);
481 local_irq_save(flags);
482 clock_zeros(master, FSI_MASTER_DPOLL_CLOCKS);
483 serial_out(master, &cmd);
485 local_irq_restore(flags);
488 dev_warn(master->dev,
489 "ERR slave is stuck in busy state, issuing TERM\n");
490 local_irq_save(flags);
491 clock_zeros(master, FSI_MASTER_DPOLL_CLOCKS);
492 local_irq_restore(flags);
493 issue_term(master, slave);
498 dev_dbg(master->dev, "ERRA received: 0x%x\n", (int)response.msg);
502 dev_dbg(master->dev, "ERRC received: 0x%x\n", (int)response.msg);
503 trace_fsi_master_gpio_crc_cmd_error(master);
509 trace_fsi_master_gpio_poll_response_busy(master, busy_count);
512 * tSendDelay clocks, avoids signal reflections when switching
513 * from receive of response back to send of data.
515 local_irq_save(flags);
516 clock_zeros(master, master->t_send_delay);
517 local_irq_restore(flags);
522 static int send_request(struct fsi_master_gpio *master,
523 struct fsi_gpio_msg *cmd)
527 if (master->external_mode)
530 local_irq_save(flags);
531 serial_out(master, cmd);
533 local_irq_restore(flags);
538 static int fsi_master_gpio_xfer(struct fsi_master_gpio *master, uint8_t slave,
539 struct fsi_gpio_msg *cmd, size_t resp_len, void *resp)
541 int rc = -EAGAIN, retries = 0;
543 while ((retries++) < FSI_CRC_ERR_RETRIES) {
544 rc = send_request(master, cmd);
547 rc = poll_for_response(master, slave, resp_len, resp);
551 dev_warn(master->dev, "ECRC retry %d\n", retries);
553 /* Pace it a bit before retry */
560 static int fsi_master_gpio_read(struct fsi_master *_master, int link,
561 uint8_t id, uint32_t addr, void *val, size_t size)
563 struct fsi_master_gpio *master = to_fsi_master_gpio(_master);
564 struct fsi_gpio_msg cmd;
570 mutex_lock(&master->cmd_lock);
571 build_ar_command(master, &cmd, id, addr, size, NULL);
572 rc = fsi_master_gpio_xfer(master, id, &cmd, size, val);
573 last_address_update(master, id, rc == 0, addr);
574 mutex_unlock(&master->cmd_lock);
579 static int fsi_master_gpio_write(struct fsi_master *_master, int link,
580 uint8_t id, uint32_t addr, const void *val, size_t size)
582 struct fsi_master_gpio *master = to_fsi_master_gpio(_master);
583 struct fsi_gpio_msg cmd;
589 mutex_lock(&master->cmd_lock);
590 build_ar_command(master, &cmd, id, addr, size, val);
591 rc = fsi_master_gpio_xfer(master, id, &cmd, 0, NULL);
592 last_address_update(master, id, rc == 0, addr);
593 mutex_unlock(&master->cmd_lock);
598 static int fsi_master_gpio_term(struct fsi_master *_master,
599 int link, uint8_t id)
601 struct fsi_master_gpio *master = to_fsi_master_gpio(_master);
602 struct fsi_gpio_msg cmd;
608 mutex_lock(&master->cmd_lock);
609 build_term_command(&cmd, id);
610 rc = fsi_master_gpio_xfer(master, id, &cmd, 0, NULL);
611 last_address_update(master, id, false, 0);
612 mutex_unlock(&master->cmd_lock);
617 static int fsi_master_gpio_break(struct fsi_master *_master, int link)
619 struct fsi_master_gpio *master = to_fsi_master_gpio(_master);
625 trace_fsi_master_gpio_break(master);
627 mutex_lock(&master->cmd_lock);
628 if (master->external_mode) {
629 mutex_unlock(&master->cmd_lock);
633 local_irq_save(flags);
635 set_sda_output(master, 1);
637 clock_toggle(master, FSI_PRE_BREAK_CLOCKS);
639 clock_toggle(master, FSI_BREAK_CLOCKS);
642 clock_toggle(master, FSI_POST_BREAK_CLOCKS);
644 local_irq_restore(flags);
646 last_address_update(master, 0, false, 0);
647 mutex_unlock(&master->cmd_lock);
649 /* Wait for logic reset to take effect */
655 static void fsi_master_gpio_init(struct fsi_master_gpio *master)
659 gpiod_direction_output(master->gpio_mux, 1);
660 gpiod_direction_output(master->gpio_trans, 1);
661 gpiod_direction_output(master->gpio_enable, 1);
662 gpiod_direction_output(master->gpio_clk, 1);
663 gpiod_direction_output(master->gpio_data, 1);
665 /* todo: evaluate if clocks can be reduced */
666 local_irq_save(flags);
667 clock_zeros(master, FSI_INIT_CLOCKS);
668 local_irq_restore(flags);
671 static void fsi_master_gpio_init_external(struct fsi_master_gpio *master)
673 gpiod_direction_output(master->gpio_mux, 0);
674 gpiod_direction_output(master->gpio_trans, 0);
675 gpiod_direction_output(master->gpio_enable, 1);
676 gpiod_direction_input(master->gpio_clk);
677 gpiod_direction_input(master->gpio_data);
680 static int fsi_master_gpio_link_enable(struct fsi_master *_master, int link)
682 struct fsi_master_gpio *master = to_fsi_master_gpio(_master);
688 mutex_lock(&master->cmd_lock);
689 if (!master->external_mode) {
690 gpiod_set_value(master->gpio_enable, 1);
693 mutex_unlock(&master->cmd_lock);
698 static int fsi_master_gpio_link_config(struct fsi_master *_master, int link,
699 u8 t_send_delay, u8 t_echo_delay)
701 struct fsi_master_gpio *master = to_fsi_master_gpio(_master);
706 mutex_lock(&master->cmd_lock);
707 master->t_send_delay = t_send_delay;
708 master->t_echo_delay = t_echo_delay;
709 mutex_unlock(&master->cmd_lock);
714 static ssize_t external_mode_show(struct device *dev,
715 struct device_attribute *attr, char *buf)
717 struct fsi_master_gpio *master = dev_get_drvdata(dev);
719 return snprintf(buf, PAGE_SIZE - 1, "%u\n",
720 master->external_mode ? 1 : 0);
723 static ssize_t external_mode_store(struct device *dev,
724 struct device_attribute *attr, const char *buf, size_t count)
726 struct fsi_master_gpio *master = dev_get_drvdata(dev);
731 err = kstrtoul(buf, 0, &val);
735 external_mode = !!val;
737 mutex_lock(&master->cmd_lock);
739 if (external_mode == master->external_mode) {
740 mutex_unlock(&master->cmd_lock);
744 master->external_mode = external_mode;
745 if (master->external_mode)
746 fsi_master_gpio_init_external(master);
748 fsi_master_gpio_init(master);
750 mutex_unlock(&master->cmd_lock);
752 fsi_master_rescan(&master->master);
757 static DEVICE_ATTR(external_mode, 0664,
758 external_mode_show, external_mode_store);
760 static void fsi_master_gpio_release(struct device *dev)
762 struct fsi_master_gpio *master = to_fsi_master_gpio(dev_to_fsi_master(dev));
764 of_node_put(dev_of_node(master->dev));
769 static int fsi_master_gpio_probe(struct platform_device *pdev)
771 struct fsi_master_gpio *master;
772 struct gpio_desc *gpio;
775 master = kzalloc(sizeof(*master), GFP_KERNEL);
779 master->dev = &pdev->dev;
780 master->master.dev.parent = master->dev;
781 master->master.dev.of_node = of_node_get(dev_of_node(master->dev));
782 master->master.dev.release = fsi_master_gpio_release;
783 master->last_addr = LAST_ADDR_INVALID;
785 gpio = devm_gpiod_get(&pdev->dev, "clock", 0);
787 dev_err(&pdev->dev, "failed to get clock gpio\n");
791 master->gpio_clk = gpio;
793 gpio = devm_gpiod_get(&pdev->dev, "data", 0);
795 dev_err(&pdev->dev, "failed to get data gpio\n");
799 master->gpio_data = gpio;
802 gpio = devm_gpiod_get_optional(&pdev->dev, "trans", 0);
804 dev_err(&pdev->dev, "failed to get trans gpio\n");
808 master->gpio_trans = gpio;
810 gpio = devm_gpiod_get_optional(&pdev->dev, "enable", 0);
812 dev_err(&pdev->dev, "failed to get enable gpio\n");
816 master->gpio_enable = gpio;
818 gpio = devm_gpiod_get_optional(&pdev->dev, "mux", 0);
820 dev_err(&pdev->dev, "failed to get mux gpio\n");
824 master->gpio_mux = gpio;
827 * Check if GPIO block is slow enought that no extra delays
828 * are necessary. This improves performance on ast2500 by
829 * an order of magnitude.
831 master->no_delays = device_property_present(&pdev->dev, "no-gpio-delays");
833 /* Default FSI command delays */
834 master->t_send_delay = FSI_SEND_DELAY_CLOCKS;
835 master->t_echo_delay = FSI_ECHO_DELAY_CLOCKS;
837 master->master.n_links = 1;
838 master->master.flags = FSI_MASTER_FLAG_SWCLOCK;
839 master->master.read = fsi_master_gpio_read;
840 master->master.write = fsi_master_gpio_write;
841 master->master.term = fsi_master_gpio_term;
842 master->master.send_break = fsi_master_gpio_break;
843 master->master.link_enable = fsi_master_gpio_link_enable;
844 master->master.link_config = fsi_master_gpio_link_config;
845 platform_set_drvdata(pdev, master);
846 mutex_init(&master->cmd_lock);
848 fsi_master_gpio_init(master);
850 rc = device_create_file(&pdev->dev, &dev_attr_external_mode);
854 rc = fsi_master_register(&master->master);
856 device_remove_file(&pdev->dev, &dev_attr_external_mode);
857 put_device(&master->master.dev);
868 static int fsi_master_gpio_remove(struct platform_device *pdev)
870 struct fsi_master_gpio *master = platform_get_drvdata(pdev);
872 device_remove_file(&pdev->dev, &dev_attr_external_mode);
874 fsi_master_unregister(&master->master);
879 static const struct of_device_id fsi_master_gpio_match[] = {
880 { .compatible = "fsi-master-gpio" },
884 static struct platform_driver fsi_master_gpio_driver = {
886 .name = "fsi-master-gpio",
887 .of_match_table = fsi_master_gpio_match,
889 .probe = fsi_master_gpio_probe,
890 .remove = fsi_master_gpio_remove,
893 module_platform_driver(fsi_master_gpio_driver);
894 MODULE_LICENSE("GPL");