[v4,3/4] clk: Hi6220: add stub clock driver

diff --git a/drivers/clk/hisilicon/Kconfig b/drivers/clk/hisilicon/Kconfig
index b4165ba..2c16807 100644
--- a/drivers/clk/hisilicon/Kconfig
+++ b/drivers/clk/hisilicon/Kconfig
@@ -1,6 +1,6 @@ 
 config COMMON_CLK_HI6220
 	bool "Hi6220 Clock Driver"
-	depends on ARCH_HISI || COMPILE_TEST
+	depends on (ARCH_HISI || COMPILE_TEST) && MAILBOX
 	default ARCH_HISI
 	help
 	  Build the Hisilicon Hi6220 clock driver based on the common clock framework.
diff --git a/drivers/clk/hisilicon/Makefile b/drivers/clk/hisilicon/Makefile
index 48f0116..4a1001a 100644
--- a/drivers/clk/hisilicon/Makefile
+++ b/drivers/clk/hisilicon/Makefile
@@ -7,4 +7,4 @@  obj-y	+= clk.o clkgate-separated.o clkdivider-hi6220.o
 obj-$(CONFIG_ARCH_HI3xxx)	+= clk-hi3620.o
 obj-$(CONFIG_ARCH_HIP04)	+= clk-hip04.o
 obj-$(CONFIG_ARCH_HIX5HD2)	+= clk-hix5hd2.o
-obj-$(CONFIG_COMMON_CLK_HI6220)	+= clk-hi6220.o
+obj-$(CONFIG_COMMON_CLK_HI6220)	+= clk-hi6220.o clk-hi6220-stub.o
diff --git a/drivers/clk/hisilicon/clk-hi6220-stub.c b/drivers/clk/hisilicon/clk-hi6220-stub.c
new file mode 100644
index 0000000..9337d43
--- /dev/null
+++ b/drivers/clk/hisilicon/clk-hi6220-stub.c
@@ -0,0 +1,276 @@ 
+/*
+ * Hi6220 stub clock driver
+ *
+ * Copyright (c) 2015 Hisilicon Limited.
+ * Copyright (c) 2015 Linaro Limited.
+ *
+ * Author: Leo Yan <leo.yan@linaro.org>
+ *
+ * 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/clk-provider.h>
+#include <linux/err.h>
+#include <linux/kernel.h>
+#include <linux/mfd/syscon.h>
+#include <linux/mailbox_client.h>
+#include <linux/of.h>
+#include <linux/of_device.h>
+#include <linux/regmap.h>
+
+/* Stub clocks id */
+#define HI6220_STUB_ACPU0		0
+#define HI6220_STUB_ACPU1		1
+#define HI6220_STUB_GPU			2
+#define HI6220_STUB_DDR			5
+
+/* Mailbox message */
+#define HI6220_MBOX_MSG_LEN		8
+
+#define HI6220_MBOX_FREQ		0xA
+#define HI6220_MBOX_CMD_SET		0x3
+#define HI6220_MBOX_OBJ_AP		0x0
+
+/* CPU dynamic frequency scaling */
+#define ACPU_DFS_FREQ_MAX		0x1724
+#define ACPU_DFS_CUR_FREQ		0x17CC
+#define ACPU_DFS_FLAG			0x1B30
+#define ACPU_DFS_FREQ_REQ		0x1B34
+#define ACPU_DFS_FREQ_LMT		0x1B38
+#define ACPU_DFS_LOCK_FLAG		0xAEAEAEAE
+
+#define to_stub_clk(hw) container_of(hw, struct hi6220_stub_clk, hw)
+
+struct hi6220_stub_clk {
+	u32 id;
+
+	struct device *dev;
+	struct clk_hw hw;
+
+	struct regmap *dfs_map;
+	struct mbox_client cl;
+	struct mbox_chan *mbox;
+};
+
+struct hi6220_mbox_msg {
+	unsigned char type;
+	unsigned char cmd;
+	unsigned char obj;
+	unsigned char src;
+	unsigned char para[4];
+};
+
+union hi6220_mbox_data {
+	unsigned int data[HI6220_MBOX_MSG_LEN];
+	struct hi6220_mbox_msg msg;
+};
+
+static unsigned int hi6220_acpu_get_freq(struct hi6220_stub_clk *stub_clk)
+{
+	unsigned int freq;
+
+	regmap_read(stub_clk->dfs_map, ACPU_DFS_CUR_FREQ, &freq);
+	return freq;
+}
+
+static int hi6220_acpu_set_freq(struct hi6220_stub_clk *stub_clk,
+				unsigned int freq)
+{
+	union hi6220_mbox_data data;
+
+	/* set the frequency in sram */
+	regmap_write(stub_clk->dfs_map, ACPU_DFS_FREQ_REQ, freq);
+
+	/* compound mailbox message */
+	data.msg.type = HI6220_MBOX_FREQ;
+	data.msg.cmd  = HI6220_MBOX_CMD_SET;
+	data.msg.obj  = HI6220_MBOX_OBJ_AP;
+	data.msg.src  = HI6220_MBOX_OBJ_AP;
+
+	mbox_send_message(stub_clk->mbox, &data);
+	return 0;
+}
+
+static int hi6220_acpu_round_freq(struct hi6220_stub_clk *stub_clk,
+				  unsigned int freq)
+{
+	unsigned int limit_flag, limit_freq = UINT_MAX;
+	unsigned int max_freq;
+
+	/* check the constrained frequency */
+	regmap_read(stub_clk->dfs_map, ACPU_DFS_FLAG, &limit_flag);
+	if (limit_flag == ACPU_DFS_LOCK_FLAG)
+		regmap_read(stub_clk->dfs_map, ACPU_DFS_FREQ_LMT, &limit_freq);
+
+	/* check the supported maximum frequency */
+	regmap_read(stub_clk->dfs_map, ACPU_DFS_FREQ_MAX, &max_freq);
+
+	/* calculate the real maximum frequency */
+	max_freq = min(max_freq, limit_freq);
+
+	if (WARN_ON(freq > max_freq))
+		freq = max_freq;
+
+	return freq;
+}
+
+static unsigned long hi6220_stub_clk_recalc_rate(struct clk_hw *hw,
+		unsigned long parent_rate)
+{
+	u32 rate = 0;
+	struct hi6220_stub_clk *stub_clk = to_stub_clk(hw);
+
+	switch (stub_clk->id) {
+	case HI6220_STUB_ACPU0:
+		rate = hi6220_acpu_get_freq(stub_clk);
+
+		/* convert from kHz to Hz */
+		rate *= 1000;
+		break;
+
+	default:
+		dev_err(stub_clk->dev, "%s: un-supported clock id %d\n",
+			__func__, stub_clk->id);
+		break;
+	}
+
+	return rate;
+}
+
+static int hi6220_stub_clk_set_rate(struct clk_hw *hw, unsigned long rate,
+                    unsigned long parent_rate)
+{
+	struct hi6220_stub_clk *stub_clk = to_stub_clk(hw);
+	unsigned long new_rate = rate / 1000;  /* kHz */
+	int ret = 0;
+
+	switch (stub_clk->id) {
+	case HI6220_STUB_ACPU0:
+		ret = hi6220_acpu_set_freq(stub_clk, new_rate);
+		if (ret < 0)
+			return ret;
+
+		break;
+
+	default:
+		dev_err(stub_clk->dev, "%s: un-supported clock id %d\n",
+			__func__, stub_clk->id);
+		break;
+	}
+
+	pr_debug("%s: set rate=%ldkHz\n", __func__, new_rate);
+	return ret;
+}
+
+static long hi6220_stub_clk_round_rate(struct clk_hw *hw, unsigned long rate,
+		unsigned long *parent_rate)
+{
+	struct hi6220_stub_clk *stub_clk = to_stub_clk(hw);
+	unsigned long new_rate = rate / 1000;  /* kHz */
+
+	switch (stub_clk->id) {
+	case HI6220_STUB_ACPU0:
+		new_rate = hi6220_acpu_round_freq(stub_clk, new_rate);
+
+		/* convert from kHz to Hz */
+		new_rate *= 1000;
+		break;
+
+	default:
+		dev_err(stub_clk->dev, "%s: un-supported clock id %d\n",
+			__func__, stub_clk->id);
+		break;
+	}
+
+	return new_rate;
+}
+
+static const struct clk_ops hi6220_stub_clk_ops = {
+	.recalc_rate	= hi6220_stub_clk_recalc_rate,
+	.round_rate	= hi6220_stub_clk_round_rate,
+	.set_rate	= hi6220_stub_clk_set_rate,
+};
+
+static int hi6220_stub_clk_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct clk_init_data init;
+	struct hi6220_stub_clk *stub_clk;
+	struct clk *clk;
+	struct device_node *np = pdev->dev.of_node;
+	int ret;
+
+	stub_clk = devm_kzalloc(dev, sizeof(*stub_clk), GFP_KERNEL);
+	if (!stub_clk)
+		return -ENOMEM;
+
+	stub_clk->dfs_map = syscon_regmap_lookup_by_phandle(np,
+				"hisilicon,hi6220-clk-sram");
+	if (IS_ERR(stub_clk->dfs_map)) {
+		dev_err(dev, "failed to get sram regmap\n");
+		return PTR_ERR(stub_clk->dfs_map);
+	}
+
+	stub_clk->hw.init = &init;
+	stub_clk->dev = dev;
+	stub_clk->id = HI6220_STUB_ACPU0;
+
+	/* Use mailbox client with blocking mode */
+	stub_clk->cl.dev = dev;
+	stub_clk->cl.tx_done = NULL;
+	stub_clk->cl.tx_block = true;
+	stub_clk->cl.tx_tout = 500;
+	stub_clk->cl.knows_txdone = false;
+
+	/* Allocate mailbox channel */
+	stub_clk->mbox = mbox_request_channel(&stub_clk->cl, 0);
+	if (IS_ERR(stub_clk->mbox)) {
+		dev_err(dev, "failed get mailbox channel\n");
+		return PTR_ERR(stub_clk->mbox);
+	};
+
+	init.name = "acpu0";
+	init.ops = &hi6220_stub_clk_ops;
+	init.num_parents = 0;
+	init.flags = CLK_IS_ROOT;
+
+	clk = devm_clk_register(dev, &stub_clk->hw);
+	if (IS_ERR(clk))
+		return PTR_ERR(clk);
+
+	ret = of_clk_add_provider(np, of_clk_src_simple_get, clk);
+	if (ret) {
+		dev_err(dev, "failed to register OF clock provider\n");
+		return ret;
+	}
+
+	/* initialize buffer to zero */
+	regmap_write(stub_clk->dfs_map, ACPU_DFS_FLAG, 0x0);
+	regmap_write(stub_clk->dfs_map, ACPU_DFS_FREQ_REQ, 0x0);
+	regmap_write(stub_clk->dfs_map, ACPU_DFS_FREQ_LMT, 0x0);
+
+	dev_dbg(dev, "Registered clock '%s'\n", init.name);
+	return 0;
+}
+
+static const struct of_device_id hi6220_stub_clk_of_match[] = {
+	{ .compatible = "hisilicon,hi6220-stub-clk", },
+	{}
+};
+
+static struct platform_driver hi6220_stub_clk_driver = {
+	.driver	= {
+		.name = "hi6220-stub-clk",
+		.of_match_table = hi6220_stub_clk_of_match,
+	},
+	.probe = hi6220_stub_clk_probe,
+};
+
+static int __init hi6220_stub_clk_init(void)
+{
+	return platform_driver_register(&hi6220_stub_clk_driver);
+}
+subsys_initcall(hi6220_stub_clk_init);