fpga: add altera freeze bridge support

Add a low level driver for Altera Freeze Bridges to the FPGA Bridge
framework. A freeze bridge is a bridge that exists in the FPGA
fabric to isolate one region of the FPGA from the busses while that
one region is being reprogrammed.

Signed-off-by: Alan Tull <[e-mail]>
Signed-off-by: Matthew Gerlach <[e-mail]>
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/fpga/Kconfig

···
 	  Say Y to enable drivers for FPGA bridges for Altera SOCFPGA
 	  devices.
 
+config ALTERA_FREEZE_BRIDGE
+	tristate "Altera FPGA Freeze Bridge"
+	depends on ARCH_SOCFPGA && FPGA_BRIDGE
+	help
+	  Say Y to enable drivers for Altera FPGA Freeze bridges.  A
+	  freeze bridge is a bridge that exists in the FPGA fabric to
+	  isolate one region of the FPGA from the busses while that
+	  region is being reprogrammed.
+
 endif # FPGA
 
 endmenu

drivers/fpga/Makefile

···
 # FPGA Bridge Drivers
 obj-$(CONFIG_FPGA_BRIDGE)		+= fpga-bridge.o
 obj-$(CONFIG_SOCFPGA_FPGA_BRIDGE)	+= altera-hps2fpga.o altera-fpga2sdram.o
+obj-$(CONFIG_ALTERA_FREEZE_BRIDGE)	+= altera-freeze-bridge.o
 
 # High Level Interfaces
 obj-$(CONFIG_FPGA_REGION)		+= fpga-region.o

drivers/fpga/altera-freeze-bridge.c

···
+/*
+ * FPGA Freeze Bridge Controller
+ *
+ *  Copyright (C) 2016 Altera Corporation. All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+#include <linux/delay.h>
+#include <linux/io.h>
+#include <linux/kernel.h>
+#include <linux/of_device.h>
+#include <linux/module.h>
+#include <linux/fpga/fpga-bridge.h>
+
+#define FREEZE_CSR_STATUS_OFFSET		0
+#define FREEZE_CSR_CTRL_OFFSET			4
+#define FREEZE_CSR_ILLEGAL_REQ_OFFSET		8
+#define FREEZE_CSR_REG_VERSION			12
+
+#define FREEZE_CSR_SUPPORTED_VERSION		2
+
+#define FREEZE_CSR_STATUS_FREEZE_REQ_DONE	BIT(0)
+#define FREEZE_CSR_STATUS_UNFREEZE_REQ_DONE	BIT(1)
+
+#define FREEZE_CSR_CTRL_FREEZE_REQ		BIT(0)
+#define FREEZE_CSR_CTRL_RESET_REQ		BIT(1)
+#define FREEZE_CSR_CTRL_UNFREEZE_REQ		BIT(2)
+
+#define FREEZE_BRIDGE_NAME			"freeze"
+
+struct altera_freeze_br_data {
+	struct device *dev;
+	void __iomem *base_addr;
+	bool enable;
+};
+
+/*
+ * Poll status until status bit is set or we have a timeout.
+ */
+static int altera_freeze_br_req_ack(struct altera_freeze_br_data *priv,
+				    u32 timeout, u32 req_ack)
+{
+	struct device *dev = priv->dev;
+	void __iomem *csr_illegal_req_addr = priv->base_addr +
+					     FREEZE_CSR_ILLEGAL_REQ_OFFSET;
+	u32 status, illegal, ctrl;
+	int ret = -ETIMEDOUT;
+
+	do {
+		illegal = readl(csr_illegal_req_addr);
+		if (illegal) {
+			dev_err(dev, "illegal request detected 0x%x", illegal);
+
+			writel(1, csr_illegal_req_addr);
+
+			illegal = readl(csr_illegal_req_addr);
+			if (illegal)
+				dev_err(dev, "illegal request not cleared 0x%x",
+					illegal);
+
+			ret = -EINVAL;
+			break;
+		}
+
+		status = readl(priv->base_addr + FREEZE_CSR_STATUS_OFFSET);
+		dev_dbg(dev, "%s %x %x\n", __func__, status, req_ack);
+		status &= req_ack;
+		if (status) {
+			ctrl = readl(priv->base_addr + FREEZE_CSR_CTRL_OFFSET);
+			dev_dbg(dev, "%s request %x acknowledged %x %x\n",
+				__func__, req_ack, status, ctrl);
+			ret = 0;
+			break;
+		}
+
+		udelay(1);
+	} while (timeout--);
+
+	if (ret == -ETIMEDOUT)
+		dev_err(dev, "%s timeout waiting for 0x%x\n",
+			__func__, req_ack);
+
+	return ret;
+}
+
+static int altera_freeze_br_do_freeze(struct altera_freeze_br_data *priv,
+				      u32 timeout)
+{
+	struct device *dev = priv->dev;
+	void __iomem *csr_ctrl_addr = priv->base_addr +
+				      FREEZE_CSR_CTRL_OFFSET;
+	u32 status;
+	int ret;
+
+	status = readl(priv->base_addr + FREEZE_CSR_STATUS_OFFSET);
+
+	dev_dbg(dev, "%s %d %d\n", __func__, status, readl(csr_ctrl_addr));
+
+	if (status & FREEZE_CSR_STATUS_FREEZE_REQ_DONE) {
+		dev_dbg(dev, "%s bridge already disabled %d\n",
+			__func__, status);
+		return 0;
+	} else if (!(status & FREEZE_CSR_STATUS_UNFREEZE_REQ_DONE)) {
+		dev_err(dev, "%s bridge not enabled %d\n", __func__, status);
+		return -EINVAL;
+	}
+
+	writel(FREEZE_CSR_CTRL_FREEZE_REQ, csr_ctrl_addr);
+
+	ret = altera_freeze_br_req_ack(priv, timeout,
+				       FREEZE_CSR_STATUS_FREEZE_REQ_DONE);
+
+	if (ret)
+		writel(0, csr_ctrl_addr);
+	else
+		writel(FREEZE_CSR_CTRL_RESET_REQ, csr_ctrl_addr);
+
+	return ret;
+}
+
+static int altera_freeze_br_do_unfreeze(struct altera_freeze_br_data *priv,
+					u32 timeout)
+{
+	struct device *dev = priv->dev;
+	void __iomem *csr_ctrl_addr = priv->base_addr +
+				      FREEZE_CSR_CTRL_OFFSET;
+	u32 status;
+	int ret;
+
+	writel(0, csr_ctrl_addr);
+
+	status = readl(priv->base_addr + FREEZE_CSR_STATUS_OFFSET);
+
+	dev_dbg(dev, "%s %d %d\n", __func__, status, readl(csr_ctrl_addr));
+
+	if (status & FREEZE_CSR_STATUS_UNFREEZE_REQ_DONE) {
+		dev_dbg(dev, "%s bridge already enabled %d\n",
+			__func__, status);
+		return 0;
+	} else if (!(status & FREEZE_CSR_STATUS_FREEZE_REQ_DONE)) {
+		dev_err(dev, "%s bridge not frozen %d\n", __func__, status);
+		return -EINVAL;
+	}
+
+	writel(FREEZE_CSR_CTRL_UNFREEZE_REQ, csr_ctrl_addr);
+
+	ret = altera_freeze_br_req_ack(priv, timeout,
+				       FREEZE_CSR_STATUS_UNFREEZE_REQ_DONE);
+
+	status = readl(priv->base_addr + FREEZE_CSR_STATUS_OFFSET);
+
+	dev_dbg(dev, "%s %d %d\n", __func__, status, readl(csr_ctrl_addr));
+
+	writel(0, csr_ctrl_addr);
+
+	return ret;
+}
+
+/*
+ * enable = 1 : allow traffic through the bridge
+ * enable = 0 : disable traffic through the bridge
+ */
+static int altera_freeze_br_enable_set(struct fpga_bridge *bridge,
+				       bool enable)
+{
+	struct altera_freeze_br_data *priv = bridge->priv;
+	struct fpga_image_info *info = bridge->info;
+	u32 timeout = 0;
+	int ret;
+
+	if (enable) {
+		if (info)
+			timeout = info->enable_timeout_us;
+
+		ret = altera_freeze_br_do_unfreeze(bridge->priv, timeout);
+	} else {
+		if (info)
+			timeout = info->disable_timeout_us;
+
+		ret = altera_freeze_br_do_freeze(bridge->priv, timeout);
+	}
+
+	if (!ret)
+		priv->enable = enable;
+
+	return ret;
+}
+
+static int altera_freeze_br_enable_show(struct fpga_bridge *bridge)
+{
+	struct altera_freeze_br_data *priv = bridge->priv;
+
+	return priv->enable;
+}
+
+static struct fpga_bridge_ops altera_freeze_br_br_ops = {
+	.enable_set = altera_freeze_br_enable_set,
+	.enable_show = altera_freeze_br_enable_show,
+};
+
+static const struct of_device_id altera_freeze_br_of_match[] = {
+	{ .compatible = "altr,freeze-bridge-controller", },
+	{},
+};
+MODULE_DEVICE_TABLE(of, altera_freeze_br_of_match);
+
+static int altera_freeze_br_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct device_node *np = pdev->dev.of_node;
+	struct altera_freeze_br_data *priv;
+	struct resource *res;
+	u32 status, revision;
+
+	if (!np)
+		return -ENODEV;
+
+	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	priv->dev = dev;
+
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	priv->base_addr = devm_ioremap_resource(dev, res);
+	if (IS_ERR(priv->base_addr))
+		return PTR_ERR(priv->base_addr);
+
+	status = readl(priv->base_addr + FREEZE_CSR_STATUS_OFFSET);
+	if (status & FREEZE_CSR_STATUS_UNFREEZE_REQ_DONE)
+		priv->enable = 1;
+
+	revision = readl(priv->base_addr + FREEZE_CSR_REG_VERSION);
+	if (revision != FREEZE_CSR_SUPPORTED_VERSION)
+		dev_warn(dev,
+			 "%s Freeze Controller unexpected revision %d != %d\n",
+			 __func__, revision, FREEZE_CSR_SUPPORTED_VERSION);
+
+	return fpga_bridge_register(dev, FREEZE_BRIDGE_NAME,
+				    &altera_freeze_br_br_ops, priv);
+}
+
+static int altera_freeze_br_remove(struct platform_device *pdev)
+{
+	fpga_bridge_unregister(&pdev->dev);
+
+	return 0;
+}
+
+static struct platform_driver altera_freeze_br_driver = {
+	.probe = altera_freeze_br_probe,
+	.remove = altera_freeze_br_remove,
+	.driver = {
+		.name	= "altera_freeze_br",
+		.of_match_table = of_match_ptr(altera_freeze_br_of_match),
+	},
+};
+
+module_platform_driver(altera_freeze_br_driver);
+
+MODULE_DESCRIPTION("Altera Freeze Bridge");
+MODULE_AUTHOR("Alan Tull <[e-mail]>");
+MODULE_LICENSE("GPL v2");