Date:   Wed,  2 Nov 2016 11:42:46 -0400
From:   Anurup M <anurupvasu@...il.com>
To:     anurup.m@...wei.com, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Cc:     will.deacon@....com, mark.rutland@....com,
        zhangshaokun@...ilicon.com, xuwei5@...ilicon.com,
        john.garry@...wei.com, gabriele.paoloni@...wei.com,
        sanil.kumar@...ilicon.com, shyju.pv@...wei.com,
        tanxiaojun@...wei.com, shiju.jose@...wei.com, linuxarm@...wei.com
Subject: [PATCH v1 03/11] drivers: soc: hisi: Add support for Hisilicon Djtag driver

From: Tan Xiaojun <tanxiaojun@...wei.com>

	The Hisilicon Djtag is an independent component which connects
	with some other components in the SoC by Debug Bus. This driver
	can be configured to access the registers of connecting components
	(like L3 cache) during real time debugging.

Signed-off-by: Tan Xiaojun <tanxiaojun@...wei.com>
Signed-off-by: John Garry <john.garry@...wei.com>
Signed-off-by: Anurup M <anurup.m@...wei.com>
---
 drivers/soc/Kconfig                 |   1 +
 drivers/soc/Makefile                |   1 +
 drivers/soc/hisilicon/Kconfig       |  12 +
 drivers/soc/hisilicon/Makefile      |   1 +
 drivers/soc/hisilicon/djtag.c       | 639 ++++++++++++++++++++++++++++++++++++
 include/linux/soc/hisilicon/djtag.h |  38 +++
 6 files changed, 692 insertions(+)
 create mode 100644 drivers/soc/hisilicon/Kconfig
 create mode 100644 drivers/soc/hisilicon/Makefile
 create mode 100644 drivers/soc/hisilicon/djtag.c
 create mode 100644 include/linux/soc/hisilicon/djtag.h

diff --git a/drivers/soc/Kconfig b/drivers/soc/Kconfig
index e6e90e8..89ecd42 100644
--- a/drivers/soc/Kconfig
+++ b/drivers/soc/Kconfig
@@ -3,6 +3,7 @@ menu "SOC (System On Chip) specific Drivers"
 source "drivers/soc/bcm/Kconfig"
 source "drivers/soc/fsl/qbman/Kconfig"
 source "drivers/soc/fsl/qe/Kconfig"
+source "drivers/soc/hisilicon/Kconfig"
 source "drivers/soc/mediatek/Kconfig"
 source "drivers/soc/qcom/Kconfig"
 source "drivers/soc/rockchip/Kconfig"
diff --git a/drivers/soc/Makefile b/drivers/soc/Makefile
index 50c23d0..ce2beb5 100644
--- a/drivers/soc/Makefile
+++ b/drivers/soc/Makefile
@@ -6,6 +6,7 @@ obj-y				+= bcm/
 obj-$(CONFIG_ARCH_DOVE)		+= dove/
 obj-$(CONFIG_MACH_DOVE)		+= dove/
 obj-y				+= fsl/
+obj-$(CONFIG_ARCH_HISI)		+= hisilicon/
 obj-$(CONFIG_ARCH_MEDIATEK)	+= mediatek/
 obj-$(CONFIG_ARCH_QCOM)		+= qcom/
 obj-$(CONFIG_ARCH_RENESAS)	+= renesas/
diff --git a/drivers/soc/hisilicon/Kconfig b/drivers/soc/hisilicon/Kconfig
new file mode 100644
index 0000000..6dd4ba0
--- /dev/null
+++ b/drivers/soc/hisilicon/Kconfig
@@ -0,0 +1,12 @@
+#
+# Hisilicon SoC drivers
+#
+config HISI_DJTAG
+	bool "Hisilicon Djtag Support"
+	depends on ARCH_HISI || COMPILE_TEST
+	help
+	  Say y here to enable the Hisilicon Djtag support. It is
+	  an independent component which connects with some other
+	  components in the SoC by Debug Bus. This driver can be
+	  configured to access the registers of connecting
+	  components during real time debugging.
diff --git a/drivers/soc/hisilicon/Makefile b/drivers/soc/hisilicon/Makefile
new file mode 100644
index 0000000..35a7b4b
--- /dev/null
+++ b/drivers/soc/hisilicon/Makefile
@@ -0,0 +1 @@
+obj-$(CONFIG_HISI_DJTAG)	+= djtag.o
diff --git a/drivers/soc/hisilicon/djtag.c b/drivers/soc/hisilicon/djtag.c
new file mode 100644
index 0000000..a87c8b6
--- /dev/null
+++ b/drivers/soc/hisilicon/djtag.c
@@ -0,0 +1,639 @@
+/*
+ * Driver for Hisilicon Djtag r/w via System Controller.
+ *
+ * Copyright (C) 2016 Hisilicon Ltd.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/bitops.h>
+#include <linux/init.h>
+#include <linux/list.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/of_address.h>
+#include <linux/of_device.h>
+#include <linux/platform_device.h>
+#include <linux/slab.h>
+#include <linux/spinlock.h>
+
+#include <asm-generic/delay.h>
+#include <linux/soc/hisilicon/djtag.h>
+
+#define SC_DJTAG_TIMEOUT		100000	/* 100ms */
+
+/* for djtag v1 */
+#define SC_DJTAG_MSTR_EN		0x6800
+#define DJTAG_NOR_CFG			BIT(1)	/* accelerate R,W */
+#define DJTAG_MSTR_EN			BIT(0)
+#define SC_DJTAG_MSTR_START_EN		0x6804
+#define DJTAG_MSTR_START_EN		0x1
+#define SC_DJTAG_DEBUG_MODULE_SEL	0x680c
+#define SC_DJTAG_MSTR_WR		0x6810
+#define DJTAG_MSTR_W			0x1
+#define DJTAG_MSTR_R			0x0
+#define SC_DJTAG_CHAIN_UNIT_CFG_EN	0x6814
+#define CHAIN_UNIT_CFG_EN		0xFFFF
+#define SC_DJTAG_MSTR_ADDR		0x6818
+#define SC_DJTAG_MSTR_DATA		0x681c
+#define SC_DJTAG_RD_DATA_BASE		0xe800
+
+/* for djtag v2 */
+#define SC_DJTAG_SEC_ACC_EN_EX		0xd800
+#define DJTAG_SEC_ACC_EN_EX		0x1
+#define SC_DJTAG_MSTR_CFG_EX		0xd818
+#define DJTAG_MSTR_RW_SHIFT_EX		29
+#define DJTAG_MSTR_RD_EX		(0x0 << DJTAG_MSTR_RW_SHIFT_EX)
+#define DJTAG_MSTR_WR_EX		(0x1 << DJTAG_MSTR_RW_SHIFT_EX)
+#define DEBUG_MODULE_SEL_SHIFT_EX	16
+#define CHAIN_UNIT_CFG_EN_EX		0xFFFF
+#define SC_DJTAG_MSTR_ADDR_EX		0xd810
+#define SC_DJTAG_MSTR_DATA_EX		0xd814
+#define SC_DJTAG_MSTR_START_EN_EX	0xd81c
+#define DJTAG_MSTR_START_EN_EX		0x1
+#define SC_DJTAG_RD_DATA_BASE_EX	0xe800
+#define SC_DJTAG_OP_ST_EX		0xe828
+#define DJTAG_OP_DONE_EX		BIT(8)
+
+#define DJTAG_PREFIX "hisi-djtag-dev-"
+
+DEFINE_IDR(djtag_hosts_idr);
+
+struct hisi_djtag_host {
+	spinlock_t lock;
+	int id;
+	struct device dev;
+	struct list_head client_list;
+	void __iomem *sysctl_reg_map;
+	struct device_node *of_node;
+	int (*djtag_readwrite)(void __iomem *regs_base, u32 offset,
+			u32 mod_sel, u32 mod_mask, bool is_w,
+			u32 wval, int chain_id, u32 *rval);
+};
+
+#define to_hisi_djtag_client(d) container_of(d, struct hisi_djtag_client, dev)
+#define to_hisi_djtag_driver(d) container_of(d, struct hisi_djtag_driver, \
+								 driver)
+#define MODULE_PREFIX "hisi_djtag:"
+
+static void djtag_read32_relaxed(void __iomem *regs_base, u32 off, u32 *value)
+{
+	void __iomem *reg_addr = regs_base + off;
+
+	*value = readl_relaxed(reg_addr);
+}
+
+static void djtag_write32(void __iomem *regs_base, u32 off, u32 val)
+{
+	void __iomem *reg_addr = regs_base + off;
+
+	writel(val, reg_addr);
+}
+
+/*
+ * djtag_readwrite_v1/v2: djtag read/write interface
+ * @reg_base:	djtag register base address
+ * @offset:	register's offset
+ * @mod_sel:	module selection
+ * @mod_mask:	mask to select specific modules for write
+ * @is_w:	write -> true, read -> false
+ * @wval:	value to register for write
+ * @chain_id:	which sub module for read
+ * @rval:	value in register for read
+ *
+ * Return non-zero if error, else return 0.
+ */
+static int djtag_readwrite_v1(void __iomem *regs_base, u32 offset, u32 mod_sel,
+		u32 mod_mask, bool is_w, u32 wval, int chain_id, u32 *rval)
+{
+	u32 rd;
+	int timeout = SC_DJTAG_TIMEOUT;
+
+	if (!(mod_mask & CHAIN_UNIT_CFG_EN)) {
+		pr_warn("djtag: do nothing.\n");
+		return 0;
+	}
+
+	/* djtag mster enable & accelerate R,W */
+	djtag_write32(regs_base, SC_DJTAG_MSTR_EN,
+			DJTAG_NOR_CFG | DJTAG_MSTR_EN);
+
+	/* select module */
+	djtag_write32(regs_base, SC_DJTAG_DEBUG_MODULE_SEL, mod_sel);
+	djtag_write32(regs_base, SC_DJTAG_CHAIN_UNIT_CFG_EN,
+				mod_mask & CHAIN_UNIT_CFG_EN);
+
+	if (is_w) {
+		djtag_write32(regs_base, SC_DJTAG_MSTR_WR, DJTAG_MSTR_W);
+		djtag_write32(regs_base, SC_DJTAG_MSTR_DATA, wval);
+	} else
+		djtag_write32(regs_base, SC_DJTAG_MSTR_WR, DJTAG_MSTR_R);
+
+	/* address offset */
+	djtag_write32(regs_base, SC_DJTAG_MSTR_ADDR, offset);
+
+	/* start to write to djtag register */
+	djtag_write32(regs_base, SC_DJTAG_MSTR_START_EN, DJTAG_MSTR_START_EN);
+
+	/* ensure the djtag operation is done */
+	do {
+		djtag_read32_relaxed(regs_base, SC_DJTAG_MSTR_START_EN, &rd);
+		if (!(rd & DJTAG_MSTR_EN))
+			break;
+
+		udelay(1);
+	} while (timeout--);
+
+	if (timeout < 0) {
+		pr_err("djtag: %s timeout!\n", is_w ? "write" : "read");
+		return -EBUSY;
+	}
+
+	if (!is_w)
+		djtag_read32_relaxed(regs_base,
+			SC_DJTAG_RD_DATA_BASE + chain_id * 0x4, rval);
+
+	return 0;
+}
+
+static int djtag_readwrite_v2(void __iomem *regs_base, u32 offset, u32 mod_sel,
+		u32 mod_mask, bool is_w, u32 wval, int chain_id, u32 *rval)
+{
+	u32 rd;
+	int timeout = SC_DJTAG_TIMEOUT;
+
+	if (!(mod_mask & CHAIN_UNIT_CFG_EN_EX)) {
+		pr_warn("djtag: do nothing.\n");
+		return 0;
+	}
+
+	/* djtag mster enable */
+	djtag_write32(regs_base, SC_DJTAG_SEC_ACC_EN_EX, DJTAG_SEC_ACC_EN_EX);
+
+	if (is_w) {
+		djtag_write32(regs_base, SC_DJTAG_MSTR_CFG_EX, DJTAG_MSTR_WR_EX
+				| (mod_sel << DEBUG_MODULE_SEL_SHIFT_EX)
+				| (mod_mask & CHAIN_UNIT_CFG_EN_EX));
+		djtag_write32(regs_base, SC_DJTAG_MSTR_DATA_EX, wval);
+	} else
+		djtag_write32(regs_base, SC_DJTAG_MSTR_CFG_EX, DJTAG_MSTR_RD_EX
+				| (mod_sel << DEBUG_MODULE_SEL_SHIFT_EX)
+				| (mod_mask & CHAIN_UNIT_CFG_EN_EX));
+
+	/* address offset */
+	djtag_write32(regs_base, SC_DJTAG_MSTR_ADDR_EX, offset);
+
+	/* start to write to djtag register */
+	djtag_write32(regs_base,
+		      SC_DJTAG_MSTR_START_EN_EX, DJTAG_MSTR_START_EN_EX);
+
+	/* ensure the djtag operation is done */
+	do {
+		djtag_read32_relaxed(regs_base, SC_DJTAG_MSTR_START_EN_EX, &rd);
+
+		if (!(rd & DJTAG_MSTR_START_EN_EX))
+			break;
+
+		udelay(1);
+	} while (timeout--);
+
+	if (timeout < 0)
+		goto timeout;
+
+	timeout = SC_DJTAG_TIMEOUT;
+	do {
+		djtag_read32_relaxed(regs_base, SC_DJTAG_OP_ST_EX, &rd);
+
+		if (rd & DJTAG_OP_DONE_EX)
+			break;
+
+		udelay(1);
+	} while (timeout--);
+
+	if (timeout < 0)
+		goto timeout;
+
+	if (!is_w)
+		djtag_read32_relaxed(regs_base,
+				     SC_DJTAG_RD_DATA_BASE_EX + chain_id * 0x4,
+									rval);
+
+	return 0;
+
+timeout:
+	pr_err("djtag: %s timeout!\n", is_w ? "write" : "read");
+	return -EBUSY;
+}
+
+
+/**
+ * djtag_writel - write registers via djtag
+ * @node:	djtag node
+ * @offset:	register's offset
+ * @mod_sel:	module selection
+ * @mod_mask:	mask to select specific modules
+ * @val:	value to write to register
+ *
+ * If error return errno, otherwise return 0.
+ */
+int hisi_djtag_writel(struct hisi_djtag_client *client, u32 offset, u32 mod_sel,
+							u32 mod_mask, u32 val)
+{
+	void __iomem *reg_map = client->host->sysctl_reg_map;
+	unsigned long flags;
+	int ret = 0;
+
+	spin_lock_irqsave(&client->host->lock, flags);
+	ret = client->host->djtag_readwrite(reg_map, offset, mod_sel, mod_mask,
+					true, val, 0, NULL);
+	if (ret)
+		pr_err("djtag_writel: error! ret=%d\n", ret);
+	spin_unlock_irqrestore(&client->host->lock, flags);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(hisi_djtag_writel);
+
+/**
+ * djtag_readl - read registers via djtag
+ * @node:	djtag node
+ * @offset:	register's offset
+ * @mod_sel:	module type selection
+ * @chain_id:	chain_id number, mostly is 0
+ * @val:	register's value
+ *
+ * If error return errno, otherwise return 0.
+ */
+int hisi_djtag_readl(struct hisi_djtag_client *client, u32 offset, u32 mod_sel,
+							int chain_id, u32 *val)
+{
+	void __iomem *reg_map = client->host->sysctl_reg_map;
+	unsigned long flags;
+	int ret = 0;
+
+	spin_lock_irqsave(&client->host->lock, flags);
+	ret = client->host->djtag_readwrite(reg_map, offset, mod_sel,
+			0xffff, false, 0, chain_id, val);
+	if (ret)
+		pr_err("djtag_readl: error! ret=%d\n", ret);
+	spin_unlock_irqrestore(&client->host->lock, flags);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(hisi_djtag_readl);
+
+static const struct of_device_id djtag_of_match[] = {
+	/* for hip05(D02) cpu die */
+	{ .compatible = "hisilicon,hip05-cpu-djtag-v1",
+		.data = (void *)djtag_readwrite_v1 },
+	/* for hip05(D02) io die */
+	{ .compatible = "hisilicon,hip05-io-djtag-v1",
+		.data = (void *)djtag_readwrite_v1 },
+	/* for hip06(D03) cpu die */
+	{ .compatible = "hisilicon,hip06-cpu-djtag-v1",
+		.data = (void *)djtag_readwrite_v1 },
+	/* for hip06(D03) io die */
+	{ .compatible = "hisilicon,hip06-io-djtag-v2",
+		.data = (void *)djtag_readwrite_v2 },
+	/* for hip07(D05) cpu die */
+	{ .compatible = "hisilicon,hip07-cpu-djtag-v2",
+		.data = (void *)djtag_readwrite_v2 },
+	/* for hip07(D05) io die */
+	{ .compatible = "hisilicon,hip07-io-djtag-v2",
+		.data = (void *)djtag_readwrite_v2 },
+	{},
+};
+
+MODULE_DEVICE_TABLE(of, djtag_of_match);
+
+static ssize_t
+show_modalias(struct device *dev, struct device_attribute *attr, char *buf)
+{
+	struct hisi_djtag_client *client = to_hisi_djtag_client(dev);
+
+	return sprintf(buf, "%s%s\n", MODULE_PREFIX, client->name);
+}
+static DEVICE_ATTR(modalias, 0444, show_modalias, NULL);
+
+static struct attribute *hisi_djtag_dev_attrs[] = {
+	NULL,
+	/* modalias helps coldplug:  modprobe $(cat .../modalias) */
+	&dev_attr_modalias.attr,
+	NULL
+};
+ATTRIBUTE_GROUPS(hisi_djtag_dev);
+
+static struct device_type hisi_djtag_client_type = {
+	.groups		= hisi_djtag_dev_groups,
+};
+
+struct hisi_djtag_client *hisi_djtag_verify_client(struct device *dev)
+{
+	return (dev->type == &hisi_djtag_client_type)
+			? to_hisi_djtag_client(dev)
+			: NULL;
+}
+
+static int hisi_djtag_device_probe(struct device *dev)
+{
+	struct hisi_djtag_driver *driver;
+	struct hisi_djtag_client *client;
+	int rc;
+
+	client = hisi_djtag_verify_client(dev);
+	if (!client) {
+		dev_err(dev, "could not find client\n");
+		return -ENODEV;
+	}
+
+	driver = to_hisi_djtag_driver(dev->driver);
+	if (!driver) {
+		dev_err(dev, "could not find driver\n");
+		return -ENODEV;
+	}
+
+	rc = driver->probe(client);
+	if (rc < 0) {
+		dev_err(dev, "client probe failed\n");
+		return rc;
+	}
+
+	return 0;
+}
+
+static int hisi_djtag_device_remove(struct device *dev)
+{
+	struct hisi_djtag_driver *driver;
+	struct hisi_djtag_client *client;
+	int rc;
+
+	client = hisi_djtag_verify_client(dev);
+	if (!client) {
+		dev_err(dev, "could not find client\n");
+		return -ENODEV;
+	}
+
+	driver = to_hisi_djtag_driver(dev->driver);
+	if (!driver) {
+		dev_err(dev, "could not find driver\n");
+		return -ENODEV;
+	}
+
+	rc = driver->remove(client);
+	if (rc < 0) {
+		dev_err(dev, "client probe failed\n");
+		return rc;
+	}
+
+	return 0;
+}
+
+static int hisi_djtag_device_match(struct device *dev,
+					struct device_driver *drv)
+{
+	const struct of_device_id *p;
+	struct hisi_djtag_client *client = hisi_djtag_verify_client(dev);
+
+	if (!client)
+		return false;
+
+	if (of_driver_match_device(dev, drv))
+		return true;
+
+	p = of_match_device(drv->of_match_table, dev);
+	if (!p)
+		return false;
+
+	return true;
+}
+
+struct bus_type hisi_djtag_bus = {
+	.name		= "hisi-djtag",
+	.match		= hisi_djtag_device_match,
+	.probe		= hisi_djtag_device_probe,
+	.remove		= hisi_djtag_device_remove,
+};
+
+struct hisi_djtag_client *hisi_djtag_new_device(struct hisi_djtag_host *host,
+						struct device_node *node)
+{
+	struct hisi_djtag_client *client;
+	int status;
+
+	client = kzalloc(sizeof(*client), GFP_KERNEL);
+	if (!client)
+		return NULL;
+
+	client->host = host;
+
+	client->dev.parent = &client->host->dev;
+	client->dev.bus = &hisi_djtag_bus;
+	client->dev.type = &hisi_djtag_client_type;
+	client->dev.of_node = node;
+	snprintf(client->name, DJTAG_CLIENT_NAME_LEN, "%s%s",
+					DJTAG_PREFIX, node->name);
+	dev_set_name(&client->dev, "%s", client->name);
+
+	status = device_register(&client->dev);
+	if (status < 0) {
+		pr_err("error adding new device, status=%d\n", status);
+		kfree(client);
+		return NULL;
+	}
+
+	return client;
+}
+
+static struct hisi_djtag_client *hisi_djtag_of_register_device(
+						struct hisi_djtag_host *host,
+						struct device_node *node)
+{
+	struct hisi_djtag_client *client;
+
+	client = hisi_djtag_new_device(host, node);
+	if (client == NULL) {
+		dev_err(&host->dev, "error registering device %s\n",
+			node->full_name);
+		of_node_put(node);
+		return ERR_PTR(-EINVAL);
+	}
+
+	return client;
+}
+
+static void djtag_register_devices(struct hisi_djtag_host *host)
+{
+	struct device_node *node;
+	struct hisi_djtag_client *client;
+
+	if (!host->of_node)
+		return;
+
+	for_each_available_child_of_node(host->of_node, node) {
+		if (of_node_test_and_set_flag(node, OF_POPULATED))
+			continue;
+		client = hisi_djtag_of_register_device(host, node);
+		list_add(&client->next, &host->client_list);
+	}
+}
+
+static int hisi_djtag_add_host(struct hisi_djtag_host *host)
+{
+	int rc;
+
+	host->dev.bus = &hisi_djtag_bus;
+
+	rc = idr_alloc(&djtag_hosts_idr, host, 0, 0, GFP_KERNEL);
+	if (rc < 0) {
+		dev_err(&host->dev, "No available djtag host ID'!s\n");
+		return rc;
+	}
+	host->id = rc;
+
+	/* Suffix the unique ID and set djtag hostname */
+	dev_set_name(&host->dev, "djtag-host-%d", host->id);
+
+	rc = device_register(&host->dev);
+	if (rc < 0) {
+		dev_err(&host->dev, "add_host dev register failed, rc=%d\n",
+									rc);
+		idr_remove(&djtag_hosts_idr, host->id);
+		return rc;
+	}
+
+	djtag_register_devices(host);
+
+	return 0;
+}
+
+static int djtag_host_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct hisi_djtag_host *host;
+	const struct of_device_id *of_id;
+	struct resource *res;
+	int rc;
+
+	of_id = of_match_device(djtag_of_match, dev);
+	if (!of_id)
+		return -EINVAL;
+
+	host = kzalloc(sizeof(*host), GFP_KERNEL);
+	if (!host)
+		return -ENOMEM;
+
+	host->of_node = dev->of_node;
+	host->djtag_readwrite = of_id->data;
+	spin_lock_init(&host->lock);
+
+	INIT_LIST_HEAD(&host->client_list);
+
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	if (!res) {
+		dev_err(&pdev->dev, "No reg resorces!\n");
+		kfree(host);
+		return -EINVAL;
+	}
+
+	if (!resource_size(res)) {
+		dev_err(&pdev->dev, "Zero reg entry!\n");
+		kfree(host);
+		return -EINVAL;
+	}
+
+	host->sysctl_reg_map = devm_ioremap_resource(dev, res);
+	if (IS_ERR(host->sysctl_reg_map)) {
+		dev_warn(dev, "Unable to map sysctl registers.\n");
+		kfree(host);
+		return -EINVAL;
+	}
+
+	platform_set_drvdata(pdev, host);
+
+	rc = hisi_djtag_add_host(host);
+	if (rc) {
+		dev_err(dev, "add host failed, rc=%d\n", rc);
+		kfree(host);
+		return rc;
+	}
+
+	return 0;
+}
+
+static int djtag_host_remove(struct platform_device *pdev)
+{
+	struct hisi_djtag_host *host;
+	struct hisi_djtag_client *client, *tmp;
+	struct list_head *client_list;
+
+	host = platform_get_drvdata(pdev);
+	client_list = &host->client_list;
+
+	list_for_each_entry_safe(client, tmp, client_list, next) {
+		list_del(&client->next);
+		kfree(client);
+	}
+
+	device_unregister(&host->dev);
+	idr_remove(&djtag_hosts_idr, host->id);
+	kfree(host);
+
+	return 0;
+}
+
+static struct platform_driver djtag_dev_driver = {
+	.driver = {
+		.name = "hisi-djtag",
+		.of_match_table = djtag_of_match,
+	},
+	.probe = djtag_host_probe,
+	.remove = djtag_host_remove,
+};
+module_platform_driver(djtag_dev_driver);
+
+int hisi_djtag_register_driver(struct module *owner,
+				struct hisi_djtag_driver *driver)
+{
+	int rc;
+
+	driver->driver.owner = owner;
+	driver->driver.bus = &hisi_djtag_bus;
+
+	rc = driver_register(&driver->driver);
+	if (rc < 0)
+		pr_err("%s register failed, rc=%d\n", __func__, rc);
+
+	return rc;
+}
+
+void hisi_djtag_unregister_driver(struct hisi_djtag_driver *driver)
+{
+	driver->driver.bus = &hisi_djtag_bus;
+	driver_unregister(&driver->driver);
+}
+
+static int __init hisi_djtag_init(void)
+{
+	int rc;
+
+	rc = bus_register(&hisi_djtag_bus);
+	if (rc) {
+		pr_err("hisi  djtag init failed, rc=%d\n", rc);
+		return rc;
+	}
+
+	return 0;
+}
+module_init(hisi_djtag_init);
+
+static void __exit hisi_djtag_exit(void)
+{
+	bus_unregister(&hisi_djtag_bus);
+}
+module_exit(hisi_djtag_exit);
+
+MODULE_DESCRIPTION("Hisilicon djtag driver");
+MODULE_LICENSE("GPL");
+MODULE_VERSION("1.0");
diff --git a/include/linux/soc/hisilicon/djtag.h b/include/linux/soc/hisilicon/djtag.h
new file mode 100644
index 0000000..aae3bca
--- /dev/null
+++ b/include/linux/soc/hisilicon/djtag.h
@@ -0,0 +1,38 @@
+/*
+ * Driver for Hisilicon djtag r/w via System Controller.
+ *
+ * Copyright (C) 2016-2017 Hisilicon Ltd.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#ifndef __HISI_DJTAG_H
+#define __HISI_DJTAG_H
+
+#define DJTAG_CLIENT_NAME_LEN 24
+
+struct hisi_djtag_client {
+	struct hisi_djtag_host *host;
+	struct list_head next;
+	char name[DJTAG_CLIENT_NAME_LEN];
+	struct device dev;
+};
+
+struct hisi_djtag_driver {
+	struct device_driver driver;
+	int (*probe)(struct hisi_djtag_client *);
+	int (*remove)(struct hisi_djtag_client *);
+};
+
+extern struct bus_type hisi_djtag_bus;
+
+int hisi_djtag_register_driver(struct module *owner,
+				struct hisi_djtag_driver *driver);
+void hisi_djtag_unregister_driver(struct hisi_djtag_driver *driver);
+int hisi_djtag_readl(struct hisi_djtag_client *client, u32 offset,
+					u32 mod_sel, int chain_id, u32 *val);
+int hisi_djtag_writel(struct hisi_djtag_client *client, u32 offset,
+					u32 mod_sel, u32 mod_mask, u32 val);
+#endif /* __HISI_DJTAG_H */
-- 
2.1.4

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