lketc-win32/driver-knc-spi-fpga.c

/*
 * cgminer driver for KnCminer devices
 *
 * Copyright 2013 Con Kolivas <kernel@kolivas.org>
 * Copyright 2013 KnCminer
 *
 * 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; either version 3 of the License, or (at your option)
 * any later version.  See COPYING for more details.
 */

#include <stdlib.h>
#include <assert.h>
#include <fcntl.h>
#include <limits.h>
#include <unistd.h>
#include <sys/ioctl.h>
#include <linux/types.h>
#include <linux/spi/spidev.h>

#include "logging.h"
#include "miner.h"

#define MAX_SPIS		1
#define	MAX_BYTES_IN_SPI_XSFER	4096
/* /dev/spidevB.C, where B = bus, C = chipselect */
#define SPI_DEVICE_TEMPLATE	"/dev/spidev%d.%d"
#define SPI_MODE		(SPI_CPHA | SPI_CPOL | SPI_CS_HIGH)
#define SPI_BITS_PER_WORD	32
#define SPI_MAX_SPEED		3000000
#define SPI_DELAY_USECS		0
/* Max number of ASICs permitted on one SPI device */
#define MAX_ASICS		6
#define CORES_PER_ASIC	192

/* How many hardware errors in a row before disabling the core */
#define HW_ERR_LIMIT		10
#define DISA_ERR_LIMIT		3

#define MAX_ACTIVE_WORKS	(192 * 2 * 6 * 2)

#define WORK_MIDSTATE_WORDS	8
#define WORK_DATA_WORDS		3

#define WORK_STALE_US		60000000

#define	SECONDS_IN_MINUTE	60

/* Keep core disabled for no longer than 15 minutes */
#define CORE_DISA_PERIOD_US	(15 * SECONDS_IN_MINUTE * 1000000)

/* DP = Disable Policy */
bool opt_knc_DP_checkworkid = false;
bool opt_knc_DP_disable_permanently = false;

struct spidev_context {
	int fd;
	uint32_t speed;
	uint16_t delay;
	uint8_t mode;
	uint8_t bits;
};

struct spi_request {
#define	CMD_NOP		0
#define	CMD_GET_VERSION	1
#define	CMD_SUBMIT_WORK	2
#define	CMD_FLUSH_QUEUE	3

#define	WORK_ID_MASK	0x7FFF

#if (__BYTE_ORDER__ == __ORDER_BIG_ENDIAN__)
	uint32_t cmd		:4;
	uint32_t rsvd		:1; /* set to zero */
	uint32_t queue_id	:12;
	uint32_t work_id	:15;
#else
	uint32_t work_id	:15;
	uint32_t queue_id	:12;
	uint32_t rsvd		:1; /* set to zero */
	uint32_t cmd		:4;
#endif
	uint32_t midstate[WORK_MIDSTATE_WORDS];
	uint32_t data[WORK_DATA_WORDS];
};

struct spi_response {
#define	RESPONSE_TYPE_NOP		0
#define	RESPONSE_TYPE_NONCE_FOUND	1
#define	RESPONSE_TYPE_WORK_DONE		2
#if (__BYTE_ORDER__ == __ORDER_BIG_ENDIAN__)
	uint32_t type		:2;
	uint32_t asic		:3;
	uint32_t queue_id	:12;
	uint32_t work_id	:15;
#else
	uint32_t work_id	:15;
	uint32_t queue_id	:12;
	uint32_t asic		:3;
	uint32_t type		:2;
#endif
	uint32_t nonce;
	uint32_t core;
};

#define MAX_REQUESTS_IN_BATCH	( MAX_BYTES_IN_SPI_XSFER /	\
				  sizeof(struct spi_request)	\
				)

static struct spi_request spi_txbuf[MAX_REQUESTS_IN_BATCH];

#define MAX_RESPONSES_IN_BATCH	( (sizeof(spi_txbuf) - 12) /	\
				   sizeof(struct spi_response)	\
				)

struct spi_rx_t {
#if (__BYTE_ORDER__ == __ORDER_BIG_ENDIAN__)
	uint32_t rsvd_1			:31;
	uint32_t response_queue_full	:1;
#else
	uint32_t response_queue_full	:1;
	uint32_t rsvd_1			:31;
#endif
#if (__BYTE_ORDER__ == __ORDER_BIG_ENDIAN__)
	uint32_t rsvd_2			:16;
	uint32_t works_accepted		:16;
#else
	uint32_t works_accepted		:16;
	uint32_t rsvd_2			:16;
#endif
	uint32_t rsvd_3;
	struct spi_response responses[MAX_RESPONSES_IN_BATCH];
};

static struct spi_rx_t spi_rxbuf;

struct active_work {
	struct work *work;
	uint32_t work_id;
	struct timeval begin;
};

struct core_disa_data {
	struct timeval disa_begin;
	uint8_t asic;
	uint8_t core;
};

struct knc_state {
	struct spidev_context *ctx;
	int devices;
	uint32_t salt;
	uint32_t next_work_id;

	/* read - last read item, next is at (read + 1) mod BUFSIZE
	 * write - next write item, last written at (write - 1) mod BUFSIZE
	 *  When buffer is empty, read + 1 == write
	 *  Buffer full condition: read == write
	 */
	int read_q, write_q;
#define KNC_QUEUED_BUFFER_SIZE	(MAX_REQUESTS_IN_BATCH + 1)
	struct active_work queued_fifo[KNC_QUEUED_BUFFER_SIZE];

	int read_a, write_a;
#define KNC_ACTIVE_BUFFER_SIZE	(MAX_ACTIVE_WORKS + 1)
	struct active_work active_fifo[KNC_ACTIVE_BUFFER_SIZE];

	uint8_t hwerrs[MAX_ASICS * 256];
	uint8_t disa_cnt[MAX_ASICS * 256];
	uint32_t hwerr_work_id[MAX_ASICS * 256];
	int read_d, write_d;
#define KNC_DISA_CORES_SIZE	(MAX_ASICS * 256)
	struct core_disa_data disa_cores_fifo[KNC_DISA_CORES_SIZE];

	/* Local stats */
#define	KNC_MINUTES_IN_STATS_BUFFER	60
	unsigned int last_hour_shares[MAX_ASICS][256][KNC_MINUTES_IN_STATS_BUFFER + 1];
	unsigned int last_hour_hwerrs[MAX_ASICS][256][KNC_MINUTES_IN_STATS_BUFFER + 1];
	unsigned int last_hour_shares_index[MAX_ASICS][256];
	unsigned int last_hour_hwerrs_index[MAX_ASICS][256];

	pthread_mutex_t lock;
};

static inline bool knc_queued_fifo_full(struct knc_state *knc)
{
	return (knc->read_q == knc->write_q);
}

static inline bool knc_active_fifo_full(struct knc_state *knc)
{
	return (knc->read_a == knc->write_a);
}

static inline void knc_queued_fifo_inc_idx(int *idx)
{
	if (unlikely(*idx >= ((int)KNC_QUEUED_BUFFER_SIZE - 1)))
		*idx = 0;
	else
		++(*idx);
}

static inline void knc_active_fifo_inc_idx(int *idx)
{
	if (unlikely(*idx >= (KNC_ACTIVE_BUFFER_SIZE - 1)))
		*idx = 0;
	else
		++(*idx);
}

static inline void knc_disa_cores_fifo_inc_idx(int *idx)
{
	if (unlikely(*idx >= (KNC_DISA_CORES_SIZE - 1)))
		*idx = 0;
	else
		++(*idx);
}

/* Find SPI device with index idx, init it */
static struct spidev_context *spi_new(int idx)
{
	struct spidev_context *ctx;
	char dev_fname[PATH_MAX];

	if (NULL == (ctx = malloc(sizeof(struct spidev_context)))) {
		applog(LOG_ERR, "KnC spi: Out of memory");
		goto l_exit_error;
	}
	ctx->mode = SPI_MODE;
	ctx->bits = SPI_BITS_PER_WORD;
	ctx->speed = SPI_MAX_SPEED;
	ctx->delay = SPI_DELAY_USECS;

	ctx->fd = -1;

	sprintf(dev_fname, SPI_DEVICE_TEMPLATE,
		idx, /* bus */
		0    /* chipselect */
	       );
	if (0 > (ctx->fd = open(dev_fname, O_RDWR))) {
		applog(LOG_ERR, "KnC spi: Can not open SPI device %s: %m",
		       dev_fname);
		goto l_free_exit_error;
	}

	/*
	 * spi mode
	 */
	if (0 > ioctl(ctx->fd, SPI_IOC_WR_MODE, &ctx->mode))
		goto l_ioctl_error;
	if (0 > ioctl(ctx->fd, SPI_IOC_RD_MODE, &ctx->mode))
		goto l_ioctl_error;

	/*
	 * bits per word
	 */
	if (0 > ioctl(ctx->fd, SPI_IOC_WR_BITS_PER_WORD, &ctx->bits))
		goto l_ioctl_error;
	if (0 > ioctl(ctx->fd, SPI_IOC_RD_BITS_PER_WORD, &ctx->bits))
		goto l_ioctl_error;

	/*
	 * max speed hz
	 */
	if (0 > ioctl(ctx->fd, SPI_IOC_WR_MAX_SPEED_HZ, &ctx->speed))
		goto l_ioctl_error;
	if (0 > ioctl(ctx->fd, SPI_IOC_RD_MAX_SPEED_HZ, &ctx->speed))
		goto l_ioctl_error;

	applog(LOG_INFO, "KnC spi: device %s uses mode %hhu, bits %hhu, speed %u",
	       dev_fname, ctx->mode, ctx->bits, ctx->speed);

	return ctx;

l_ioctl_error:
	applog(LOG_ERR, "KnC spi: ioctl error on SPI device %s: %m", dev_fname);
	close(ctx->fd);
l_free_exit_error:
	free(ctx);
l_exit_error:
	return NULL;
}

static void spi_free(struct spidev_context *ctx)
{
	if (NULL == ctx)
		return;

	close(ctx->fd);
	free(ctx);
}

static int spi_transfer(struct spidev_context *ctx, uint8_t *txbuf,
			uint8_t *rxbuf, int len)
{
	struct spi_ioc_transfer xfr;
	int ret;

	memset(rxbuf, 0xff, len);

	ret = len;

	xfr.tx_buf = (unsigned long)txbuf;
	xfr.rx_buf = (unsigned long)rxbuf;
	xfr.len = len;
	xfr.speed_hz = ctx->speed;
	xfr.delay_usecs = ctx->delay;
	xfr.bits_per_word = ctx->bits;
	xfr.cs_change = 0;
	xfr.pad = 0;

	if (1 > (ret = ioctl(ctx->fd, SPI_IOC_MESSAGE(1), &xfr)))
		applog(LOG_ERR, "KnC spi xfer: ioctl error on SPI device: %m");

	return ret;
}

static void stats_zero_data_if_curindex_updated(unsigned int *data, unsigned int *index, unsigned int cur_index)
{
	if (cur_index != *index) {
		unsigned int i;
		for (i = (*index + 1) % (KNC_MINUTES_IN_STATS_BUFFER + 1);
			 i != cur_index;
			 i = ((i + 1 ) % (KNC_MINUTES_IN_STATS_BUFFER + 1)))
			data[i] = 0;
		data[cur_index] = 0;
		*index = cur_index;
	}
}

static void stats_update(unsigned int *data, unsigned int *index, unsigned int cur_index)
{
	stats_zero_data_if_curindex_updated(data, index, cur_index);
	++(data[cur_index]);
}

static unsigned int get_accumulated_stats(unsigned int *data, unsigned int *index, unsigned int cur_index)
{
	unsigned int res, i;

	stats_zero_data_if_curindex_updated(data, index, cur_index);

	res = 0;
	for (i = 0; i < (KNC_MINUTES_IN_STATS_BUFFER + 1); ++i) {
		if (i != cur_index)
			res += data[i];
	}

	return res;
}

static inline void stats_good_share(struct knc_state *knc, uint32_t asic, uint32_t core, struct timespec *ts)
{
	if ((asic >= MAX_ASICS) || (core >= 256))
		return;
	unsigned int cur_minute = (ts->tv_sec / SECONDS_IN_MINUTE) % (KNC_MINUTES_IN_STATS_BUFFER + 1);
	stats_update(knc->last_hour_shares[asic][core], &(knc->last_hour_shares_index[asic][core]), cur_minute);
}

static inline void stats_bad_share(struct knc_state *knc, uint32_t asic, uint32_t core, struct timespec *ts)
{
	if ((asic >= MAX_ASICS) || (core >= 256))
		return;
	unsigned int cur_minute = (ts->tv_sec / SECONDS_IN_MINUTE) % (KNC_MINUTES_IN_STATS_BUFFER + 1);
	stats_update(knc->last_hour_hwerrs[asic][core], &(knc->last_hour_hwerrs_index[asic][core]), cur_minute);
}

static inline unsigned int get_hour_shares(struct knc_state *knc, uint32_t asic, uint32_t core, struct timespec *ts)
{
	if ((asic >= MAX_ASICS) || (core >= 256))
		return 0;
	unsigned int cur_minute = (ts->tv_sec / SECONDS_IN_MINUTE) % (KNC_MINUTES_IN_STATS_BUFFER + 1);
	return get_accumulated_stats(knc->last_hour_shares[asic][core], &(knc->last_hour_shares_index[asic][core]), cur_minute);
}

static inline unsigned int get_hour_errors(struct knc_state *knc, uint32_t asic, uint32_t core, struct timespec *ts)
{
	if ((asic >= MAX_ASICS) || (core >= 256))
		return 0;
	unsigned int cur_minute = (ts->tv_sec / SECONDS_IN_MINUTE) % (KNC_MINUTES_IN_STATS_BUFFER + 1);
	return get_accumulated_stats(knc->last_hour_hwerrs[asic][core], &(knc->last_hour_hwerrs_index[asic][core]), cur_minute);
}

static struct api_data *knc_api_stats(struct cgpu_info *cgpu)
{
	struct knc_state *knc = cgpu->device_data;
	struct api_data *root = NULL;
	unsigned int cursize;
	int asic, core, n;
	char buf[4096];
	struct timespec ts_now;

	clock_gettime(CLOCK_MONOTONIC, &ts_now);

	for (asic = 0; asic < MAX_ASICS; ++asic) {
		char asic_name[128];
		snprintf(asic_name, sizeof(asic_name), "asic_%d_shares", asic + 1);
		cursize = 0;
		for (core = 0; core < CORES_PER_ASIC; ++core) {
			unsigned int shares = get_hour_shares(knc, asic, core, &ts_now);
			n = snprintf(buf + cursize, sizeof(buf) - cursize, "%d,", shares);
			cursize += n;
			if (sizeof(buf) < cursize) {
				cursize = sizeof(buf);
				break;
			}
		}
		if (0 < cursize)
			buf[cursize - 1] = '\0'; /* last comma */
		root = api_add_string(root, asic_name, buf, true);

		snprintf(asic_name, sizeof(asic_name), "asic_%d_hwerrs", asic + 1);
		cursize = 0;
		for (core = 0; core < CORES_PER_ASIC; ++core) {
			unsigned int errors = get_hour_errors(knc, asic, core, &ts_now);
			n = snprintf(buf + cursize, sizeof(buf) - cursize, "%d,", errors);
			cursize += n;
			if (sizeof(buf) < cursize) {
				cursize = sizeof(buf);
				break;
			}
		}
		if (0 < cursize)
			buf[cursize - 1] = '\0'; /* last comma */
		root = api_add_string(root, asic_name, buf, true);
	}

	return root;
}

static void disable_core(uint8_t asic, uint8_t core)
{
	char str[256];

	snprintf(str, sizeof(str), "i2cset -y 2 0x2%hhu %hhu 0", asic, core);
	if (0 != WEXITSTATUS(system(str)))
		applog(LOG_ERR, "KnC: system call failed");
}

static void enable_core(uint8_t asic, uint8_t core)
{
	char str[256];

	snprintf(str, sizeof(str), "i2cset -y 2 0x2%hhu %hhu 1", asic, core);
	if (0 != WEXITSTATUS(system(str)))
		applog(LOG_ERR, "KnC: system call failed");
}

static int64_t timediff(const struct timeval *a, const struct timeval *b)
{
	struct timeval diff;

	timersub(a, b, &diff);

	return diff.tv_sec * 1000000 + diff.tv_usec;
}

static void knc_check_disabled_cores(struct knc_state *knc)
{
	struct core_disa_data *core;
	int next_read_d, cidx;
	struct timeval now;
	int64_t us;

	next_read_d = knc->read_d;
	knc_disa_cores_fifo_inc_idx(&next_read_d);
	if (next_read_d == knc->write_d)
		return; /* queue empty */

	core = &knc->disa_cores_fifo[next_read_d];
	gettimeofday(&now, NULL);
	us = timediff(&now, &core->disa_begin);
	if ((us >= 0) && (us < CORE_DISA_PERIOD_US))
		return; /* latest disabled core still not expired */

	cidx = core->asic * 256 + core->core;
	enable_core(core->asic, core->core);
	knc->hwerrs[cidx] = 0;
	applog(LOG_NOTICE,
	       "KnC: core %u-%u was enabled back from disabled state",
	       core->asic, core->core);
	knc->read_d = next_read_d;
}

static void knc_work_from_queue_to_spi(struct knc_state *knc,
				       struct active_work *q_work,
				       struct spi_request *spi_req, uint32_t work_id)
{
	uint32_t *buf_from, *buf_to;
	int i;

	spi_req->cmd = CMD_SUBMIT_WORK;
	spi_req->queue_id = 0; /* at the moment we have one and only queue #0 */
	spi_req->work_id = (work_id ^ knc->salt) & WORK_ID_MASK;
	q_work->work_id = spi_req->work_id;
	buf_to = spi_req->midstate;
	buf_from = (uint32_t *)q_work->work->midstate;

	for (i = 0; i < WORK_MIDSTATE_WORDS; ++i)
		buf_to[i] = le32toh(buf_from[8 - i - 1]);
	buf_to = spi_req->data;
	buf_from = (uint32_t *)&(q_work->work->data[16 * 4]);

	for (i = 0; i < WORK_DATA_WORDS; ++i)
		buf_to[i] = le32toh(buf_from[3 - i - 1]);
}

static int64_t knc_process_response(struct thr_info *thr, struct cgpu_info *cgpu,
				    struct spi_rx_t *rxbuf)
{
	struct knc_state *knc = cgpu->device_data;
	int submitted, successful, i, num_sent;
	int next_read_q, next_read_a;
	struct timeval now;
	struct timespec ts_now;
	struct work *work;
	int64_t us;

	num_sent = knc->write_q - knc->read_q - 1;
	if (knc->write_q <= knc->read_q)
		num_sent += KNC_QUEUED_BUFFER_SIZE;

	knc->next_work_id += rxbuf->works_accepted;

	/* Actually process SPI response */
	if (rxbuf->works_accepted) {
		applog(LOG_DEBUG, "KnC spi: raw response %08X %08X",
		       ((uint32_t *)rxbuf)[0], ((uint32_t *)rxbuf)[1]);
		applog(LOG_DEBUG,
		       "KnC spi: response, accepted %u (from %u), full %u",
		       rxbuf->works_accepted, num_sent,
		       rxbuf->response_queue_full);
	}
	/* move works_accepted number of items from queued_fifo to active_fifo */
	gettimeofday(&now, NULL);
	clock_gettime(CLOCK_MONOTONIC, &ts_now);
	submitted = 0;

	for (i = 0; i < rxbuf->works_accepted; ++i) {
		next_read_q = knc->read_q;
		knc_queued_fifo_inc_idx(&next_read_q);
		if ((next_read_q == knc->write_q) || knc_active_fifo_full(knc))
			break;

		memcpy(&knc->active_fifo[knc->write_a],
		       &knc->queued_fifo[next_read_q],
		       sizeof(struct active_work));
		knc->active_fifo[knc->write_a].begin = now;
		knc->queued_fifo[next_read_q].work = NULL;
		knc->read_q = next_read_q;
		knc_active_fifo_inc_idx(&knc->write_a);
		++submitted;
	}
	if (submitted != rxbuf->works_accepted) {
		applog(LOG_ERR,
		       "KnC: accepted by FPGA %u works, but only %d submitted",
		       rxbuf->works_accepted, submitted);
	}

	/* check for completed works and calculated nonces */
	gettimeofday(&now, NULL);
	successful = 0;

	for (i = 0; i < (int)MAX_RESPONSES_IN_BATCH; ++i) {
		if ((rxbuf->responses[i].type != RESPONSE_TYPE_NONCE_FOUND) &&
		    (rxbuf->responses[i].type != RESPONSE_TYPE_WORK_DONE))
			continue;

		applog(LOG_DEBUG, "KnC spi: raw response %08X %08X",
		       ((uint32_t *)&rxbuf->responses[i])[0],
		       ((uint32_t *)&rxbuf->responses[i])[1]);
		applog(LOG_DEBUG, "KnC spi: response, T:%u C:%u-%u Q:%u W:%u",
		       rxbuf->responses[i].type,
		       rxbuf->responses[i].asic, rxbuf->responses[i].core,
		       rxbuf->responses[i].queue_id,
		       rxbuf->responses[i].work_id);
		/* Find active work with matching ID */
		next_read_a = knc->read_a;
		knc_active_fifo_inc_idx(&next_read_a);

		while (next_read_a != knc->write_a) {
			if (knc->active_fifo[next_read_a].work_id ==
			    rxbuf->responses[i].work_id)
				break;

			/* check for stale works */
			us = timediff(&now,
				      &knc->active_fifo[next_read_a].begin);
			if ((us < 0) || (us >= WORK_STALE_US)) {
				applog(LOG_DEBUG,
				       "KnC spi: remove stale work %u",
				       knc->active_fifo[next_read_a].work_id);
				work = knc->active_fifo[next_read_a].work;
				knc_active_fifo_inc_idx(&knc->read_a);
				work_completed(cgpu, work);
				if (next_read_a != knc->read_a) {
					memcpy(&(knc->active_fifo[next_read_a]),
					       &(knc->active_fifo[knc->read_a]),
					       sizeof(struct active_work));
				}
				knc->active_fifo[knc->read_a].work = NULL;
			}

			knc_active_fifo_inc_idx(&next_read_a);
		}
		if (next_read_a == knc->write_a)
			continue;

		applog(LOG_DEBUG, "KnC spi: response work %u found",
		       rxbuf->responses[i].work_id);
		work = knc->active_fifo[next_read_a].work;

		if (rxbuf->responses[i].type == RESPONSE_TYPE_NONCE_FOUND) {
			if (NULL != thr) {
				int cidx = rxbuf->responses[i].asic * 256 +
					   rxbuf->responses[i].core;

				if (submit_nonce(thr, work,
						 rxbuf->responses[i].nonce)) {
					stats_good_share(knc, rxbuf->responses[i].asic, rxbuf->responses[i].core, &ts_now);
					if (cidx < (int)sizeof(knc->hwerrs)) {
						knc->hwerrs[cidx] = 0;
						knc->disa_cnt[cidx] = 0;
						knc->hwerr_work_id[cidx] = 0xFFFFFFFF;
					}
					successful++;
				} else  {
					stats_bad_share(knc, rxbuf->responses[i].asic, rxbuf->responses[i].core, &ts_now);
					bool process_hwerr = (cidx < (int)sizeof(knc->hwerrs));
					if (process_hwerr && opt_knc_DP_checkworkid &&
					    (knc->hwerr_work_id[cidx] == rxbuf->responses[i].work_id))
						process_hwerr = false;
					if (process_hwerr) {
						knc->hwerr_work_id[cidx] = rxbuf->responses[i].work_id;
						if (++(knc->hwerrs[cidx]) >= HW_ERR_LIMIT) {
						    struct core_disa_data *core;

						    core = &knc->disa_cores_fifo[knc->write_d];
						    core->disa_begin = now;
						    core->asic = rxbuf->responses[i].asic;
						    core->core = rxbuf->responses[i].core;
						    disable_core(core->asic, core->core);
						    if (opt_knc_DP_disable_permanently &&
							(++(knc->disa_cnt[cidx]) >= DISA_ERR_LIMIT)) {
							    applog(LOG_WARNING,
			"KnC: core %u-%u was disabled permanently", core->asic, core->core);
						    } else {
							    applog(LOG_WARNING,
			"KnC: core %u-%u was disabled due to %u HW errors in a row",
								   core->asic, core->core, HW_ERR_LIMIT);
							    knc_disa_cores_fifo_inc_idx(&knc->write_d);
						    }
						}
					}
				};
			}
			continue;
		}

		/* Work completed */
		knc_active_fifo_inc_idx(&knc->read_a);
		work_completed(cgpu, work);
		if (next_read_a != knc->read_a) {
			memcpy(&(knc->active_fifo[next_read_a]),
			       &(knc->active_fifo[knc->read_a]),
			       sizeof(struct active_work));
		}
		knc->active_fifo[knc->read_a].work = NULL;
	}

	return ((uint64_t)successful) * 0x100000000UL;
}

/* Send flush command via SPI */
static int _internal_knc_flush_fpga(struct knc_state *knc)
{
	int len;

	spi_txbuf[0].cmd = CMD_FLUSH_QUEUE;
	spi_txbuf[0].queue_id = 0; /* at the moment we have one and only queue #0 */
	len = spi_transfer(knc->ctx, (uint8_t *)spi_txbuf,
			   (uint8_t *)&spi_rxbuf, sizeof(struct spi_request));
	if (len != sizeof(struct spi_request))
		return -1;

	len /= sizeof(struct spi_response);

	return len;
}

static bool knc_detect_one(struct spidev_context *ctx)
{
	/* Scan device for ASICs */
	int chip_id, devices = 0;
	struct cgpu_info *cgpu;
	struct knc_state *knc;

	for (chip_id = 0; chip_id < MAX_ASICS; ++chip_id) {
		/* TODO: perform the ASIC test/detection */
		++devices;
	}

	if (!devices) {
		applog(LOG_INFO, "SPI detected, but not KnCminer ASICs");
		return false;
	}

	applog(LOG_INFO, "Found a KnC miner with %d ASICs", devices);

	cgpu = calloc(1, sizeof(*cgpu));
	knc = calloc(1, sizeof(*knc));
	if (!cgpu || !knc) {
		applog(LOG_ERR, "KnC miner detected, but failed to allocate memory");
		return false;
	}

	knc->ctx = ctx;
	knc->devices = devices;
	knc->read_q = 0;
	knc->write_q = 1;
	knc->read_a = 0;
	knc->write_a = 1;
	knc->read_d = 0;
	knc->write_d = 1;
	knc->salt = rand();
	mutex_init(&knc->lock);

	memset(knc->hwerr_work_id, 0xFF, sizeof(knc->hwerr_work_id));

	_internal_knc_flush_fpga(knc);

	cgpu->drv = &knc_drv;
	cgpu->name = "KnCminer";
	cgpu->threads = 1;	// .. perhaps our number of devices?

	cgpu->device_data = knc;
	add_cgpu(cgpu);

	return true;
}

// http://www.concentric.net/~Ttwang/tech/inthash.htm
static unsigned long mix(unsigned long a, unsigned long b, unsigned long c)
{
	a = a - b;  a = a - c;  a = a ^ (c >> 13);
	b = b - c;  b = b - a;  b = b ^ (a << 8);
	c = c - a;  c = c - b;  c = c ^ (b >> 13);
	a = a - b;  a = a - c;  a = a ^ (c >> 12);
	b = b - c;  b = b - a;  b = b ^ (a << 16);
	c = c - a;  c = c - b;  c = c ^ (b >> 5);
	a = a - b;  a = a - c;  a = a ^ (c >> 3);
	b = b - c;  b = b - a;  b = b ^ (a << 10);
	c = c - a;  c = c - b;  c = c ^ (b >> 15);

	return c;
}

/* Probe devices and register with add_cgpu */
void knc_detect(bool __maybe_unused hotplug)
{
	int idx;

	srand(mix(clock(), time(NULL), getpid()));

	/* Loop through all possible SPI interfaces */
	for (idx = 0; idx < MAX_SPIS; ++idx) {
		struct spidev_context *ctx = spi_new(idx + 1);

		if (ctx != NULL) {
			if (!knc_detect_one(ctx))
				spi_free(ctx);
		}
	}
}

/* return value is number of nonces that have been checked since
 * previous call
 */
static int64_t knc_scanwork(struct thr_info *thr)
{
	struct cgpu_info *cgpu = thr->cgpu;
	struct knc_state *knc = cgpu->device_data;
	int len, num, next_read_q;
	int64_t ret;

	applog(LOG_DEBUG, "KnC running scanwork");

	knc_check_disabled_cores(knc);

	num = 0;

	mutex_lock(&knc->lock);
	/* Prepare tx buffer */
	memset(spi_txbuf, 0, sizeof(spi_txbuf));
	next_read_q = knc->read_q;
	knc_queued_fifo_inc_idx(&next_read_q);

	while (next_read_q != knc->write_q) {
		knc_work_from_queue_to_spi(knc, &knc->queued_fifo[next_read_q],
					   &spi_txbuf[num], knc->next_work_id + num);
		knc_queued_fifo_inc_idx(&next_read_q);
		++num;
	}
	/* knc->read_q is advanced in knc_process_response, not here.
	 * knc->next_work_id is advanced in knc_process_response as well,
	 *   because only after SPI response we know how many works were actually
	 *   consumed by FPGA.
	 */

	len = spi_transfer(knc->ctx, (uint8_t *)spi_txbuf,
			   (uint8_t *)&spi_rxbuf, sizeof(spi_txbuf));
	if (len != sizeof(spi_rxbuf)) {
		ret = -1;
		goto out_unlock;
	}

	applog(LOG_DEBUG, "KnC spi: %d works in request", num);

	ret = knc_process_response(thr, cgpu, &spi_rxbuf);
out_unlock:
	mutex_unlock(&knc->lock);

	return ret;
}

static bool knc_queue_full(struct cgpu_info *cgpu)
{
	struct knc_state *knc = cgpu->device_data;
	int queue_full = false;
	struct work *work;

	applog(LOG_DEBUG, "KnC running queue full");

	mutex_lock(&knc->lock);
	if (knc_queued_fifo_full(knc)) {
		queue_full = true;
		goto out_unlock;
	}
	work = get_queued(cgpu);
	if (!work)
		goto out_unlock;
	knc->queued_fifo[knc->write_q].work = work;
	knc_queued_fifo_inc_idx(&(knc->write_q));
	if (knc_queued_fifo_full(knc))
		queue_full = true;
out_unlock:
	mutex_unlock(&knc->lock);

	return queue_full;
}

static void knc_flush_work(struct cgpu_info *cgpu)
{
	struct knc_state *knc = cgpu->device_data;
	int len, next_read_q, next_read_a;
	struct work *work;

	applog(LOG_ERR, "KnC running flushwork");

	mutex_lock(&knc->lock);
	/* Drain queued works */
	next_read_q = knc->read_q;
	knc_queued_fifo_inc_idx(&next_read_q);

	while (next_read_q != knc->write_q) {
		work = knc->queued_fifo[next_read_q].work;
		work_completed(cgpu, work);
		knc->queued_fifo[next_read_q].work = NULL;
		knc->read_q = next_read_q;
		knc_queued_fifo_inc_idx(&next_read_q);
	}

	/* Drain active works */
	next_read_a = knc->read_a;
	knc_active_fifo_inc_idx(&next_read_a);

	while (next_read_a != knc->write_a) {
		work = knc->active_fifo[next_read_a].work;
		work_completed(cgpu, work);
		knc->active_fifo[next_read_a].work = NULL;
		knc->read_a = next_read_a;
		knc_active_fifo_inc_idx(&next_read_a);
	}

	len = _internal_knc_flush_fpga(knc);
	if (len > 0)
		knc_process_response(NULL, cgpu, &spi_rxbuf);
	mutex_unlock(&knc->lock);
}

struct device_drv knc_drv = {
	.drv_id = DRIVER_knc,
	.dname = "KnCminer",
	.name = "KnC",
	.drv_detect = knc_detect,	// Probe for devices, add with add_cgpu

	.hash_work = hash_queued_work,
	.scanwork = knc_scanwork,
	.queue_full = knc_queue_full,
	.flush_work = knc_flush_work,

	.get_api_stats = knc_api_stats,
};