clk: Hi6220: add stub clock driver

On Hi6220, there have some clocks which can use mailbox channel to send
messages to power controller to change frequency; this includes CPU, GPU
and DDR clocks.

For dynamic frequency scaling, firstly need write the frequency value to
SRAM region, and then send message to mailbox to trigger power controller
to handle this requirement. This driver will use syscon APIs to pass SRAM
memory region and use common mailbox APIs for channels accessing.

This init driver will support cpu frequency change firstly.
Signed-off-by: Leo Yan <leo.yan@linaro.org>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>

drivers/clk/hisilicon/Kconfig

 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.

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

drivers/clk/hisilicon/clk-hi6220-stub.c

+/*
+ * 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);