drivers/fpga/efinix-spi.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * FPGA Manager Driver for Efinix
 *
 * Copyright (C) 2025 iris-GmbH infrared & intelligent sensors
 *
 * Ian Dannapel <iansdannapel@gmail.com>
 *
 * Load Efinix FPGA firmware over SPI using the serial configuration interface.
 *
 * Note: Only passive mode (host initiates transfer) is currently supported.
 */

#include <linux/delay.h>
#include <linux/fpga/fpga-mgr.h>
#include <linux/gpio/consumer.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/spi/spi.h>

/*
 * 13 dummy bytes generate 104 SPI clock cycles (8 bits each).
 * Used to meet the requirement for >100 clock cycles idle sequence.
 */
#define EFINIX_SPI_IDLE_CYCLES_BYTES 13

/*
 * tDMIN: Minimum time between deassertion of CRESET_N to first
 * valid configuration data. (32 µs)
 */
#define EFINIX_TDMIN_US_MIN    35
#define EFINIX_TDMIN_US_MAX    40

/*
 * tCRESET_N: Minimum CRESET_N low pulse width required to
 * trigger re-configuration. (320 ns)
 */
#define EFINIX_TCRESETN_DELAY_MIN_US  1
#define EFINIX_TCRESETN_DELAY_MAX_US  2

/*
 * tUSER: Minimum configuration duration after CDONE goes high
 * before entering user mode. (25 µs)
 */
#define EFINIX_TUSER_US_MIN    30
#define EFINIX_TUSER_US_MAX    35

struct efinix_spi_conf {
	struct spi_device *spi;
	struct gpio_desc *cdone;
	struct gpio_desc *reset;
};

static void efinix_spi_reset(struct efinix_spi_conf *conf)
{
	gpiod_set_value(conf->reset, 1);
	usleep_range(EFINIX_TCRESETN_DELAY_MIN_US, EFINIX_TCRESETN_DELAY_MAX_US);
	gpiod_set_value(conf->reset, 0);
	usleep_range(EFINIX_TDMIN_US_MIN, EFINIX_TDMIN_US_MAX);
}

static enum fpga_mgr_states efinix_spi_state(struct fpga_manager *mgr)
{
	struct efinix_spi_conf *conf = mgr->priv;

	if (conf->cdone && gpiod_get_value(conf->cdone) == 1)
		return FPGA_MGR_STATE_OPERATING;

	return FPGA_MGR_STATE_UNKNOWN;
}

static int efinix_spi_write_init(struct fpga_manager *mgr,
				 struct fpga_image_info *info,
				 const char *buf, size_t count)
{
	struct efinix_spi_conf *conf = mgr->priv;
	struct spi_transfer assert_cs = {
		/* Keep CS asserted across configuration. */
		.cs_change = 1,
	};
	struct spi_message message;
	int ret;

	if (info->flags & FPGA_MGR_PARTIAL_RECONFIG) {
		dev_err(&mgr->dev, "Partial reconfiguration not supported\n");
		return -EOPNOTSUPP;
	}

	/*
	 * Efinix passive SPI configuration requires chip select to stay
	 * asserted from reset until the bitstream is fully clocked in.
	 * Lock the SPI bus so no other device can toggle CS between the
	 * reset pulse and the write/complete transfers.
	 */
	spi_bus_lock(conf->spi->controller);
	spi_message_init_with_transfers(&message, &assert_cs, 1);
	ret = spi_sync_locked(conf->spi, &message);
	if (ret) {
		spi_bus_unlock(conf->spi->controller);
		return ret;
	}

	/* Reset with CS asserted */
	efinix_spi_reset(conf);

	return 0;
}

static int efinix_spi_write(struct fpga_manager *mgr, const char *buf,
			    size_t count)
{
	struct spi_transfer write_xfer = {
		.tx_buf = buf,
		.len = count,
		.cs_change = 1,
	};
	struct efinix_spi_conf *conf = mgr->priv;
	struct spi_message message;
	int ret;

	spi_message_init_with_transfers(&message, &write_xfer, 1);
	ret = spi_sync_locked(conf->spi, &message);
	if (ret) {
		dev_err(&mgr->dev, "SPI error in firmware write: %d\n", ret);
		spi_bus_unlock(conf->spi->controller);
	}

	return ret;
}

static int efinix_spi_write_complete(struct fpga_manager *mgr,
				     struct fpga_image_info *info)
{
	unsigned long timeout =
		jiffies + usecs_to_jiffies(info->config_complete_timeout_us);
	struct spi_transfer clk_cycles = {
		.len = EFINIX_SPI_IDLE_CYCLES_BYTES,
		/* Release CS after the trailing idle clocks are sent. */
		.cs_change = 0,
	};
	struct efinix_spi_conf *conf = mgr->priv;
	struct spi_message message;
	int done, ret;
	bool expired = false;
	u8 *dummy_buf;

	dummy_buf = kzalloc(EFINIX_SPI_IDLE_CYCLES_BYTES, GFP_KERNEL);
	if (!dummy_buf) {
		ret = -ENOMEM;
		goto unlock_spi;
	}

	/*
	 * Keep the bus locked while sending the trailing idle clocks, then
	 * let this final transfer deassert CS to terminate configuration.
	 */
	clk_cycles.tx_buf = dummy_buf;
	spi_message_init_with_transfers(&message, &clk_cycles, 1);
	ret = spi_sync_locked(conf->spi, &message);
	if (ret) {
		dev_err(&mgr->dev, "SPI error in write complete: %d\n", ret);
		goto free_buf;
	}

	if (conf->cdone) {
		while (!expired) {
			done = gpiod_get_value(conf->cdone);
			if (done < 0) {
				ret = done;
				goto free_buf;
			}
			if (done)
				break;

			usleep_range(10, 20);
			expired = time_after(jiffies, timeout);
		}

		if (expired) {
			dev_err(&mgr->dev, "Timeout waiting for CDONE\n");
			ret = -ETIMEDOUT;
			goto free_buf;
		}
	}

	usleep_range(EFINIX_TUSER_US_MIN, EFINIX_TUSER_US_MAX);

free_buf:
	kfree(dummy_buf);
unlock_spi:
	spi_bus_unlock(conf->spi->controller);

	return ret;
}

static const struct fpga_manager_ops efinix_spi_ops = {
	.state = efinix_spi_state,
	.write_init = efinix_spi_write_init,
	.write = efinix_spi_write,
	.write_complete = efinix_spi_write_complete,
};

static int efinix_spi_probe(struct spi_device *spi)
{
	struct efinix_spi_conf *conf;
	struct fpga_manager *mgr;

	if (!(spi->mode & SPI_CPHA) || !(spi->mode & SPI_CPOL))
		return dev_err_probe(&spi->dev, -EINVAL,
				     "Unsupported SPI mode, set CPHA and CPOL\n");

	conf = devm_kzalloc(&spi->dev, sizeof(*conf), GFP_KERNEL);
	if (!conf)
		return -ENOMEM;

	conf->reset = devm_gpiod_get(&spi->dev, "reset", GPIOD_OUT_HIGH);
	if (IS_ERR(conf->reset))
		return dev_err_probe(&spi->dev, PTR_ERR(conf->reset),
				     "Failed to get RESET gpio\n");

	conf->cdone = devm_gpiod_get_optional(&spi->dev, "cdone", GPIOD_IN);
	if (IS_ERR(conf->cdone))
		return dev_err_probe(&spi->dev, PTR_ERR(conf->cdone),
				     "Failed to get CDONE gpio\n");

	conf->spi = spi;

	mgr = devm_fpga_mgr_register(&spi->dev,
				     "Efinix FPGA Manager",
				     &efinix_spi_ops, conf);

	return PTR_ERR_OR_ZERO(mgr);
}

static const struct of_device_id efinix_spi_of_match[] = {
	{ .compatible = "efinix,trion-config", },
	{}
};
MODULE_DEVICE_TABLE(of, efinix_spi_of_match);

static const struct spi_device_id efinix_ids[] = {
	{ "trion-config", 0 },
	{},
};
MODULE_DEVICE_TABLE(spi, efinix_ids);

static struct spi_driver efinix_spi_driver = {
	.driver = {
		.name = "efinix-spi",
		.of_match_table = efinix_spi_of_match,
	},
	.probe = efinix_spi_probe,
	.id_table = efinix_ids,
};

module_spi_driver(efinix_spi_driver);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Ian Dannapel <iansdannapel@gmail.com>");
MODULE_DESCRIPTION("Efinix FPGA SPI Programming Driver");