[PATCH v9 3/3] fpga: Add support for Lattice iCE40 FPGAs

[Joel Holdsworth]

The Lattice iCE40 is a family of FPGAs with a minimalistic architecture
and very regular structure, designed for low-cost, high-volume consumer
and system applications.

This patch adds support to the FPGA manager for configuring the SRAM of
iCE40LM, iCE40LP, iCE40HX, iCE40 Ultra, iCE40 UltraLite and iCE40
UltraPlus devices, through slave SPI.

The iCE40 family is notable because it is the first FPGA family to have
complete reverse engineered bit-stream documentation for the iCE40LP and
iCE40HX devices. Furthermore, there is now a Free Software Verilog
synthesis tool-chain: the "IceStorm" tool-chain.

This project is the work of Clifford Wolf, who is the maintainer of
Yosys Verilog RTL synthesis framework, and Mathias Lasser, with notable
contributions from "Cotton Seed", the main author of "arachne-pnr"; a
place-and-route tool for iCE40 FPGAs.

Having a Free Software synthesis tool-chain offers interesting
opportunities for embedded devices that are able reconfigure themselves
with open firmware that is generated on the device itself. For example
a mobile device might have an application processor with an iCE40 FPGA
attached, which implements slave devices, or through which the processor
communicates with other devices through the FPGA fabric.

A kernel driver for the iCE40 is useful, because in some cases, the FPGA
may need to be configured before other devices can be accessed.

An example of such a device is the icoBoard; a RaspberryPI HAT which
features an iCE40HX8K with a 1 or 8 MBit SRAM and ports for
Digilent-compatible PMOD modules. A PMOD module may contain a device
with which the kernel communicates, via the FPGA.

Signed-off-by: Joel Holdsworth <joel@xxxxxxxxxxxxxxxxxxx>
---
 drivers/fpga/Kconfig     |   6 ++
 drivers/fpga/Makefile    |   1 +
 drivers/fpga/ice40-spi.c | 213 +++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 220 insertions(+)
 create mode 100644 drivers/fpga/ice40-spi.c

diff --git a/drivers/fpga/Kconfig b/drivers/fpga/Kconfig
index ce861a2..967cda4 100644
--- a/drivers/fpga/Kconfig
+++ b/drivers/fpga/Kconfig
@@ -20,6 +20,12 @@ config FPGA_REGION
 	  FPGA Regions allow loading FPGA images under control of
 	  the Device Tree.
 
+config FPGA_MGR_ICE40_SPI
+	tristate "Lattice iCE40 SPI"
+	depends on OF && SPI
+	help
+	  FPGA manager driver support for Lattice iCE40 FPGAs over SPI.
+
 config FPGA_MGR_SOCFPGA
 	tristate "Altera SOCFPGA FPGA Manager"
 	depends on ARCH_SOCFPGA || COMPILE_TEST
diff --git a/drivers/fpga/Makefile b/drivers/fpga/Makefile
index 8df07bc..cc0d364 100644
--- a/drivers/fpga/Makefile
+++ b/drivers/fpga/Makefile
@@ -6,6 +6,7 @@
 obj-$(CONFIG_FPGA)			+= fpga-mgr.o
 
 # FPGA Manager Drivers
+obj-$(CONFIG_FPGA_MGR_ICE40_SPI)	+= ice40-spi.o
 obj-$(CONFIG_FPGA_MGR_SOCFPGA)		+= socfpga.o
 obj-$(CONFIG_FPGA_MGR_SOCFPGA_A10)	+= socfpga-a10.o
 obj-$(CONFIG_FPGA_MGR_ZYNQ_FPGA)	+= zynq-fpga.o
diff --git a/drivers/fpga/ice40-spi.c b/drivers/fpga/ice40-spi.c
new file mode 100644
index 0000000..3c99859
--- /dev/null
+++ b/drivers/fpga/ice40-spi.c
@@ -0,0 +1,213 @@
+/*
+ * FPGA Manager Driver for Lattice iCE40.
+ *
+ *  Copyright (c) 2016 Joel Holdsworth
+ *
+ * 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; version 2 of the License.
+ *
+ * This driver adds support to the FPGA manager for configuring the SRAM of
+ * Lattice iCE40 FPGAs through slave SPI.
+ */
+
+#include <linux/fpga/fpga-mgr.h>
+#include <linux/gpio/consumer.h>
+#include <linux/module.h>
+#include <linux/of_gpio.h>
+#include <linux/spi/spi.h>
+
+#define ICE40_SPI_FPGAMGR_RESET_DELAY 1 /* us (>200ns) */
+#define ICE40_SPI_FPGAMGR_HOUSEKEEPING_DELAY 1200 /* us */
+
+#define ICE40_SPI_FPGAMGR_NUM_ACTIVATION_BYTES DIV_ROUND_UP(49, 8)
+
+struct ice40_fpga_priv {
+	struct spi_device *dev;
+	struct gpio_desc *reset;
+	struct gpio_desc *cdone;
+};
+
+static enum fpga_mgr_states ice40_fpga_ops_state(struct fpga_manager *mgr)
+{
+	struct ice40_fpga_priv *priv = mgr->priv;
+
+	return gpiod_get_value(priv->cdone) ? FPGA_MGR_STATE_OPERATING :
+		FPGA_MGR_STATE_UNKNOWN;
+}
+
+static int ice40_fpga_ops_write_init(struct fpga_manager *mgr,
+				     struct fpga_image_info *info,
+				     const char *buf, size_t count)
+{
+	struct ice40_fpga_priv *priv = mgr->priv;
+	struct spi_device *dev = priv->dev;
+	struct spi_message message;
+	struct spi_transfer assert_cs_then_reset_delay = {
+		.cs_change   = 1,
+		.delay_usecs = ICE40_SPI_FPGAMGR_RESET_DELAY
+	};
+	struct spi_transfer housekeeping_delay_then_release_cs = {
+		.delay_usecs = ICE40_SPI_FPGAMGR_HOUSEKEEPING_DELAY
+	};
+	int ret;
+
+	if ((info->flags & FPGA_MGR_PARTIAL_RECONFIG)) {
+		dev_err(&dev->dev,
+			"Partial reconfiguration is not supported\n");
+		return -ENOTSUPP;
+	}
+
+	/* Lock the bus, assert CRESET_B and SS_B and delay >200ns */
+	spi_bus_lock(dev->master);
+
+	gpiod_set_value(priv->reset, 1);
+
+	spi_message_init(&message);
+	spi_message_add_tail(&assert_cs_then_reset_delay, &message);
+	ret = spi_sync_locked(dev, &message);
+
+	/* Come out of reset */
+	gpiod_set_value(priv->reset, 0);
+
+	/* Abort if the chip-select failed */
+	if (ret)
+		goto fail;
+
+	/* Check CDONE is de-asserted i.e. the FPGA is reset */
+	if (gpiod_get_value(priv->cdone)) {
+		dev_err(&dev->dev, "Device reset failed, CDONE is asserted\n");
+		ret = -EIO;
+		goto fail;
+	}
+
+	/* Wait for the housekeeping to complete, and release SS_B */
+	spi_message_init(&message);
+	spi_message_add_tail(&housekeeping_delay_then_release_cs, &message);
+	ret = spi_sync_locked(dev, &message);
+
+fail:
+	spi_bus_unlock(dev->master);
+
+	return ret;
+}
+
+static int ice40_fpga_ops_write(struct fpga_manager *mgr,
+				const char *buf, size_t count)
+{
+	struct ice40_fpga_priv *priv = mgr->priv;
+
+	return spi_write(priv->dev, buf, count);
+}
+
+static int ice40_fpga_ops_write_complete(struct fpga_manager *mgr,
+					 struct fpga_image_info *info)
+{
+	struct ice40_fpga_priv *priv = mgr->priv;
+	struct spi_device *dev = priv->dev;
+	const u8 padding[ICE40_SPI_FPGAMGR_NUM_ACTIVATION_BYTES] = {0};
+
+	/* Check CDONE is asserted */
+	if (!gpiod_get_value(priv->cdone)) {
+		dev_err(&dev->dev,
+			"CDONE was not asserted after firmware transfer\n");
+		return -EIO;
+	}
+
+	/* Send of zero-padding to activate the firmware */
+	return spi_write(dev, padding, sizeof(padding));
+}
+
+static const struct fpga_manager_ops ice40_fpga_ops = {
+	.state = ice40_fpga_ops_state,
+	.write_init = ice40_fpga_ops_write_init,
+	.write = ice40_fpga_ops_write,
+	.write_complete = ice40_fpga_ops_write_complete,
+};
+
+static int ice40_fpga_probe(struct spi_device *spi)
+{
+	struct device *dev = &spi->dev;
+	struct device_node *np = spi->dev.of_node;
+	struct ice40_fpga_priv *priv;
+	int ret;
+
+	if (!np) {
+		dev_err(dev, "No Device Tree entry\n");
+		return -EINVAL;
+	}
+
+	priv = devm_kzalloc(&spi->dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	priv->dev = spi;
+
+	/* Check board setup data. */
+	if (spi->max_speed_hz > 25000000) {
+		dev_err(dev, "Speed is too high\n");
+		return -EINVAL;
+	}
+
+	if (spi->max_speed_hz < 1000000) {
+		dev_err(dev, "Speed is too low\n");
+		return -EINVAL;
+	}
+
+	if (spi->mode & SPI_CPHA) {
+		dev_err(dev, "Bad mode\n");
+		return -EINVAL;
+	}
+
+	/* Set up the GPIOs */
+	priv->cdone = devm_gpiod_get(dev, "cdone", GPIOD_IN);
+	if (IS_ERR(priv->cdone)) {
+		dev_err(dev, "Failed to get CDONE GPIO: %ld\n",
+			PTR_ERR(priv->cdone));
+		return -EINVAL;
+	}
+
+	priv->reset = devm_gpiod_get(dev, "reset", GPIOD_OUT_HIGH);
+	if (IS_ERR(priv->reset)) {
+		dev_err(dev, "Failed to get CRESET_B GPIO: %ld\n",
+			PTR_ERR(priv->reset));
+		return -EINVAL;
+	}
+
+	/* Register with the FPGA manager */
+	ret = fpga_mgr_register(dev, "Lattice iCE40 FPGA Manager",
+				&ice40_fpga_ops, priv);
+	if (ret) {
+		dev_err(dev, "Unable to register FPGA manager");
+		return ret;
+	}
+
+	return 0;
+}
+
+static int ice40_fpga_remove(struct spi_device *spi)
+{
+	fpga_mgr_unregister(&spi->dev);
+	return 0;
+}
+
+static const struct of_device_id ice40_fpga_of_match[] = {
+	{ .compatible = "lattice,ice40-fpga-mgr", },
+	{},
+};
+MODULE_DEVICE_TABLE(of, ice40_fpga_of_match);
+
+static struct spi_driver ice40_fpga_driver = {
+	.probe = ice40_fpga_probe,
+	.remove = ice40_fpga_remove,
+	.driver = {
+		.name = "ice40spi",
+		.of_match_table = of_match_ptr(ice40_fpga_of_match),
+	},
+};
+
+module_spi_driver(ice40_fpga_driver);
+
+MODULE_AUTHOR("Joel Holdsworth <joel@xxxxxxxxxxxxxxxxxxx>");
+MODULE_DESCRIPTION("Lattice iCE40 FPGA Manager");
+MODULE_LICENSE("GPL v2");
-- 
2.7.4