linux/drivers/fpga/altera-fpga2sdram.c

// SPDX-License-Identifier: GPL-2.0
/*
 * FPGA to SDRAM Bridge Driver for Altera SoCFPGA Devices
 *
 *  Copyright (C) 2013-2016 Altera Corporation, All Rights Reserved.
 */

/*
 * This driver manages a bridge between an FPGA and the SDRAM used by the ARM
 * host processor system (HPS).
 *
 * The bridge contains 4 read ports, 4 write ports, and 6 command ports.
 * Reconfiguring these ports requires that no SDRAM transactions occur during
 * reconfiguration.  The code reconfiguring the ports cannot run out of SDRAM
 * nor can the FPGA access the SDRAM during reconfiguration.  This driver does
 * not support reconfiguring the ports.  The ports are configured by code
 * running out of on chip ram before Linux is started and the configuration
 * is passed in a handoff register in the system manager.
 *
 * This driver supports enabling and disabling of the configured ports, which
 * allows for safe reprogramming of the FPGA, assuming that the new FPGA image
 * uses the same port configuration.  Bridges must be disabled before
 * reprogramming the FPGA and re-enabled after the FPGA has been programmed.
 */

#include <linux/fpga/fpga-bridge.h>
#include <linux/kernel.h>
#include <linux/mfd/syscon.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/regmap.h>

#define ALT_SDR_CTL_FPGAPORTRST_OFST		0x80
#define ALT_SDR_CTL_FPGAPORTRST_PORTRSTN_MSK	0x00003fff
#define ALT_SDR_CTL_FPGAPORTRST_RD_SHIFT	0
#define ALT_SDR_CTL_FPGAPORTRST_WR_SHIFT	4
#define ALT_SDR_CTL_FPGAPORTRST_CTRL_SHIFT	8

/*
 * From the Cyclone V HPS Memory Map document:
 *   These registers are used to store handoff information between the
 *   preloader and the OS. These 8 registers can be used to store any
 *   information. The contents of these registers have no impact on
 *   the state of the HPS hardware.
 */
#define SYSMGR_ISWGRP_HANDOFF3          (0x8C)

#define F2S_BRIDGE_NAME "fpga2sdram"

struct alt_fpga2sdram_data {
	struct device *dev;
	struct regmap *sdrctl;
	int mask;
};

static int alt_fpga2sdram_enable_show(struct fpga_bridge *bridge)
{
	struct alt_fpga2sdram_data *priv = bridge->priv;
	int value;

	regmap_read(priv->sdrctl, ALT_SDR_CTL_FPGAPORTRST_OFST, &value);

	return (value & priv->mask) == priv->mask;
}

static inline int _alt_fpga2sdram_enable_set(struct alt_fpga2sdram_data *priv,
					     bool enable)
{
	return regmap_update_bits(priv->sdrctl, ALT_SDR_CTL_FPGAPORTRST_OFST,
				  priv->mask, enable ? priv->mask : 0);
}

static int alt_fpga2sdram_enable_set(struct fpga_bridge *bridge, bool enable)
{
	return _alt_fpga2sdram_enable_set(bridge->priv, enable);
}

static const struct fpga_bridge_ops altera_fpga2sdram_br_ops = {
	.enable_set = alt_fpga2sdram_enable_set,
	.enable_show = alt_fpga2sdram_enable_show,
};

static const struct of_device_id altera_fpga_of_match[] = {
	{ .compatible = "altr,socfpga-fpga2sdram-bridge" },
	{},
};

static int alt_fpga_bridge_probe(struct platform_device *pdev)
{
	struct device *dev = &pdev->dev;
	struct alt_fpga2sdram_data *priv;
	struct fpga_bridge *br;
	u32 enable;
	struct regmap *sysmgr;
	int ret = 0;

	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
	if (!priv)
		return -ENOMEM;

	priv->dev = dev;

	priv->sdrctl = syscon_regmap_lookup_by_compatible("altr,sdr-ctl");
	if (IS_ERR(priv->sdrctl)) {
		dev_err(dev, "regmap for altr,sdr-ctl lookup failed.\n");
		return PTR_ERR(priv->sdrctl);
	}

	sysmgr = syscon_regmap_lookup_by_compatible("altr,sys-mgr");
	if (IS_ERR(sysmgr)) {
		dev_err(dev, "regmap for altr,sys-mgr lookup failed.\n");
		return PTR_ERR(sysmgr);
	}

	/* Get f2s bridge configuration saved in handoff register */
	regmap_read(sysmgr, SYSMGR_ISWGRP_HANDOFF3, &priv->mask);

	br = fpga_bridge_register(dev, F2S_BRIDGE_NAME,
				  &altera_fpga2sdram_br_ops, priv);
	if (IS_ERR(br))
		return PTR_ERR(br);

	platform_set_drvdata(pdev, br);

	dev_info(dev, "driver initialized with handoff %08x\n", priv->mask);

	if (!of_property_read_u32(dev->of_node, "bridge-enable", &enable)) {
		if (enable > 1) {
			dev_warn(dev, "invalid bridge-enable %u > 1\n", enable);
		} else {
			dev_info(dev, "%s bridge\n",
				 (enable ? "enabling" : "disabling"));
			ret = _alt_fpga2sdram_enable_set(priv, enable);
			if (ret) {
				fpga_bridge_unregister(br);
				return ret;
			}
		}
	}

	return ret;
}

static void alt_fpga_bridge_remove(struct platform_device *pdev)
{
	struct fpga_bridge *br = platform_get_drvdata(pdev);

	fpga_bridge_unregister(br);
}

MODULE_DEVICE_TABLE(of, altera_fpga_of_match);

static struct platform_driver altera_fpga_driver = {
	.probe = alt_fpga_bridge_probe,
	.remove = alt_fpga_bridge_remove,
	.driver = {
		.name	= "altera_fpga2sdram_bridge",
		.of_match_table = of_match_ptr(altera_fpga_of_match),
	},
};

module_platform_driver(altera_fpga_driver);

MODULE_DESCRIPTION("Altera SoCFPGA FPGA to SDRAM Bridge");
MODULE_AUTHOR("Alan Tull <atull@opensource.altera.com>");
MODULE_LICENSE("GPL v2");