[PATCH 3/3] clk: keystone: Add sci-clk driver support

[Nishanth Menon]

From: Tero Kristo <t-kristo@xxxxxx>

In K2G, the clock handling is done through firmware executing on a
separate core. Linux kernel needs to communicate to the firmware
through TI system control interface to access any power management
related resources, including clocks.

The keystone sci-clk driver does this, by communicating to the
firmware through the TI SCI driver. The driver adds support for
registering clocks through DT, and basic required clock operations
like prepare/get_rate, etc.

Signed-off-by: Tero Kristo <t-kristo@xxxxxx>
Tested-by: Dave Gerlach <d-gerlach@xxxxxx>
Signed-off-by: Nishanth Menon <nm@xxxxxx>
---
 MAINTAINERS                    |   1 +
 drivers/clk/Kconfig            |  13 +
 drivers/clk/keystone/Makefile  |   1 +
 drivers/clk/keystone/sci-clk.c | 539 +++++++++++++++++++++++++++++++++++++++++
 4 files changed, 554 insertions(+)
 create mode 100644 drivers/clk/keystone/sci-clk.c

diff --git a/MAINTAINERS b/MAINTAINERS
index f24aa97f845c..af06f022b725 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -11578,6 +11578,7 @@ F:	include/dt-bindings/genpd/k2g.h
 F:	drivers/soc/ti/ti_sci_pm_domains.c
 F:	Documentation/devicetree/bindings/clock/ti,sci-clk.txt
 F:	include/dt-bindings/clock/k2g.h
+F:	drivers/clk/keystone/sci-clk.c
 
 THANKO'S RAREMONO AM/FM/SW RADIO RECEIVER USB DRIVER
 M:	Hans Verkuil <hverkuil@xxxxxxxxx>
diff --git a/drivers/clk/Kconfig b/drivers/clk/Kconfig
index e2d9bd760c84..d1724999be78 100644
--- a/drivers/clk/Kconfig
+++ b/drivers/clk/Kconfig
@@ -179,6 +179,19 @@ config COMMON_CLK_NXP
 	---help---
 	  Support for clock providers on NXP platforms.
 
+if COMMON_CLK_KEYSTONE
+
+config TI_SCI_CLK
+	tristate "TI System Control Interface clock drivers"
+	depends on TI_SCI_PROTOCOL || COMPILE_TEST
+	default y
+	help
+	  This adds the clock driver support over TI System Control Interface.
+	  If you wish to use clock resources from the PMMC firmware, say Y.
+	  Otherwise, say N.
+
+endif # COMMON_CLK_KEYSTONE
+
 config COMMON_CLK_PALMAS
 	tristate "Clock driver for TI Palmas devices"
 	depends on MFD_PALMAS
diff --git a/drivers/clk/keystone/Makefile b/drivers/clk/keystone/Makefile
index 0477cf63f132..0e7993d2c09a 100644
--- a/drivers/clk/keystone/Makefile
+++ b/drivers/clk/keystone/Makefile
@@ -1 +1,2 @@
 obj-y			+= pll.o gate.o
+obj-$(CONFIG_TI_SCI_CLK)	+= sci-clk.o
diff --git a/drivers/clk/keystone/sci-clk.c b/drivers/clk/keystone/sci-clk.c
new file mode 100644
index 000000000000..6c43e097e6d6
--- /dev/null
+++ b/drivers/clk/keystone/sci-clk.c
@@ -0,0 +1,539 @@
+/*
+ * SCI Clock driver for keystone based devices
+ *
+ * Copyright (C) 2015-2016 Texas Instruments Incorporated - http://www.ti.com/
+ *	Tero Kristo <t-kristo@xxxxxx>
+ *
+ * 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.
+ *
+ * This program is distributed "as is" WITHOUT ANY WARRANTY of any
+ * kind, whether express or implied; without even the implied warranty
+ * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+#include <linux/clk.h>
+#include <linux/clk-provider.h>
+#include <linux/err.h>
+#include <linux/io.h>
+#include <linux/module.h>
+#include <linux/of_address.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/slab.h>
+#include <linux/soc/ti/ti_sci_protocol.h>
+
+#define SCI_CLK_SSC_ENABLE		BIT(0)
+#define SCI_CLK_ALLOW_FREQ_CHANGE	BIT(1)
+#define SCI_CLK_INPUT_TERMINATION	BIT(2)
+
+/**
+ * struct sci_clk_provider - TI SCI clock provider representation
+ * @sci:    Handle to the System Control Interface protocol handler
+ * @ops:    Pointer to the SCI ops to be used by the clocks
+ * @dev:    Device pointer for the clock provider
+ * @clocks: List of all registered clocks
+ * @lock:   Mutex for locking access to the @clocks list
+ */
+struct sci_clk_provider {
+	const struct ti_sci_handle *sci;
+	const struct ti_sci_clk_ops *ops;
+	struct device *dev;
+	struct list_head clocks;
+	struct mutex lock; /* Protects access to the @clocks list */
+};
+
+/**
+ * struct sci_clk - TI SCI clock representation
+ * @hw:		 Hardware clock cookie for common clock framework
+ * @dev_id:	 Device index
+ * @clk_id:	 Clock index
+ * @node:	 Clocks list link
+ * @provider:	 Master clock provider
+ * @flags:	 Flags for the clock
+ */
+struct sci_clk {
+	struct clk_hw hw;
+	u16 dev_id;
+	u8 clk_id;
+	struct list_head node;
+	struct sci_clk_provider *provider;
+	u8 flags;
+};
+
+#define to_sci_clk(_hw) container_of(_hw, struct sci_clk, hw)
+
+/**
+ * sci_clk_prepare - Prepare (enable) a TI SCI clock
+ * @hw: clock to prepare
+ *
+ * Prepares a clock to be actively used. Returns the SCI protocol status.
+ */
+static int sci_clk_prepare(struct clk_hw *hw)
+{
+	struct sci_clk *clk = to_sci_clk(hw);
+	bool enable_ssc = clk->flags & SCI_CLK_SSC_ENABLE;
+	bool allow_freq_change = clk->flags & SCI_CLK_ALLOW_FREQ_CHANGE;
+	bool input_termination = clk->flags & SCI_CLK_INPUT_TERMINATION;
+
+	return clk->provider->ops->get_clock(clk->provider->sci, clk->dev_id,
+					     clk->clk_id, enable_ssc,
+					     allow_freq_change,
+					     input_termination);
+}
+
+/**
+ * sci_clk_unprepare - Un-prepares (disables) a TI SCI clock
+ * @hw: clock to unprepare
+ *
+ * Un-prepares a clock from active state.
+ */
+static void sci_clk_unprepare(struct clk_hw *hw)
+{
+	struct sci_clk *clk = to_sci_clk(hw);
+	int ret;
+
+	ret = clk->provider->ops->put_clock(clk->provider->sci, clk->dev_id,
+					    clk->clk_id);
+	if (ret)
+		dev_err(clk->provider->dev,
+			"unprepare failed for dev=%d, clk=%d, ret=%d\n",
+			clk->dev_id, clk->clk_id, ret);
+}
+
+/**
+ * sci_clk_is_prepared - Check if a TI SCI clock is prepared or not
+ * @hw: clock to check status for
+ *
+ * Checks if a clock is prepared (enabled) in hardware. Returns non-zero
+ * value if clock is enabled, zero otherwise.
+ */
+static int sci_clk_is_prepared(struct clk_hw *hw)
+{
+	struct sci_clk *clk = to_sci_clk(hw);
+	bool req_state, current_state;
+	int ret;
+
+	ret = clk->provider->ops->is_on(clk->provider->sci, clk->dev_id,
+					clk->clk_id, &req_state,
+					&current_state);
+	if (ret) {
+		dev_err(clk->provider->dev,
+			"prepare failed for dev=%d, clk=%d, ret=%d\n",
+			clk->dev_id, clk->clk_id, ret);
+		return 0;
+	}
+
+	return req_state;
+}
+
+/**
+ * sci_clk_recalc_rate - Get clock rate for a TI SCI clock
+ * @hw: clock to get rate for
+ * @parent_rate: parent rate provided by common clock framework, not used
+ *
+ * Gets the current clock rate of a TI SCI clock. Returns the current
+ * clock rate, or zero in failure.
+ */
+static unsigned long sci_clk_recalc_rate(struct clk_hw *hw,
+					 unsigned long parent_rate)
+{
+	struct sci_clk *clk = to_sci_clk(hw);
+	u64 freq;
+	int ret;
+
+	ret = clk->provider->ops->get_freq(clk->provider->sci, clk->dev_id,
+					   clk->clk_id, &freq);
+	if (ret) {
+		dev_err(clk->provider->dev,
+			"recalc-rate failed for dev=%d, clk=%d, ret=%d\n",
+			clk->dev_id, clk->clk_id, ret);
+		return 0;
+	}
+
+	return (u32)freq;
+}
+
+/**
+ * sci_clk_determine_rate - Determines a clock rate a clock can be set to
+ * @hw: clock to change rate for
+ * @req: requested rate configuration for the clock
+ *
+ * Determines a suitable clock rate and parent for a TI SCI clock.
+ * The parent handling is un-used, as generally the parent clock rates
+ * are not known by the kernel; instead these are internally handled
+ * by the firmware. Returns the new clock rate that can be set for the
+ * clock, or 0 in failure.
+ */
+static int sci_clk_determine_rate(struct clk_hw *hw,
+				  struct clk_rate_request *req)
+{
+	struct sci_clk *clk = to_sci_clk(hw);
+	u64 new_rate;
+	int ret;
+
+	ret = clk->provider->ops->get_best_match_freq(clk->provider->sci,
+						      clk->dev_id,
+						      clk->clk_id,
+						      req->min_rate,
+						      req->rate,
+						      req->max_rate,
+						      &new_rate);
+	if (ret) {
+		dev_err(clk->provider->dev,
+			"determine-rate failed for dev=%d, clk=%d, ret=%d\n",
+			clk->dev_id, clk->clk_id, ret);
+		return 0;
+	}
+
+	return (int)new_rate;
+}
+
+/**
+ * sci_clk_set_rate - Set rate for a TI SCI clock
+ * @hw: clock to change rate for
+ * @rate: target rate for the clock
+ * @parent_rate: rate of the clock parent, not used for TI SCI clocks
+ *
+ * Sets a clock frequency for a TI SCI clock. Returns the TI SCI
+ * protocol status.
+ */
+static int sci_clk_set_rate(struct clk_hw *hw, unsigned long rate,
+			    unsigned long parent_rate)
+{
+	struct sci_clk *clk = to_sci_clk(hw);
+	u64 freq = rate;
+
+	return clk->provider->ops->set_freq(clk->provider->sci, clk->dev_id,
+					    clk->clk_id, freq, freq, freq);
+}
+
+/**
+ * sci_clk_get_parent - Get the current parent of a TI SCI clock
+ * @hw: clock to get parent for
+ *
+ * Returns the index of the currently selected parent for a TI SCI clock.
+ */
+static u8 sci_clk_get_parent(struct clk_hw *hw)
+{
+	struct sci_clk *clk = to_sci_clk(hw);
+	u8 parent_id;
+	int ret;
+
+	ret = clk->provider->ops->get_parent(clk->provider->sci, clk->dev_id,
+					     clk->clk_id, &parent_id);
+	if (ret) {
+		dev_err(clk->provider->dev,
+			"get-parent failed for dev=%d, clk=%d, ret=%d\n",
+			clk->dev_id, clk->clk_id, ret);
+		return 0;
+	}
+
+	parent_id = parent_id - clk->clk_id - 1;
+
+	return parent_id;
+}
+
+/**
+ * sci_clk_set_parent - Set the parent of a TI SCI clock
+ * @hw: clock to set parent for
+ * @index: new parent index for the clock
+ *
+ * Sets the parent of a TI SCI clock. Return TI SCI protocol status.
+ */
+static int sci_clk_set_parent(struct clk_hw *hw, u8 index)
+{
+	struct sci_clk *clk = to_sci_clk(hw);
+
+	return clk->provider->ops->set_parent(clk->provider->sci, clk->dev_id,
+					      clk->clk_id,
+					      index + 1 + clk->clk_id);
+}
+
+static const struct clk_ops sci_clk_ops = {
+	.prepare = sci_clk_prepare,
+	.unprepare = sci_clk_unprepare,
+	.is_prepared = sci_clk_is_prepared,
+	.recalc_rate = sci_clk_recalc_rate,
+	.determine_rate = sci_clk_determine_rate,
+	.set_rate = sci_clk_set_rate,
+	.get_parent = sci_clk_get_parent,
+	.set_parent = sci_clk_set_parent,
+};
+
+/**
+ * _sci_clk_get - Gets a handle for an SCI clock
+ * @provider: Handle to SCI clock provider
+ * @dev_id: device ID for the clock to register
+ * @clk_id: clock ID for the clock to register
+ * @parse_parents: indicator whether parents for this clock should be handled
+ *
+ * Gets a handle to an existing TI SCI clock, or builds a new clock
+ * entry and registers it with the common clock framework. Called from
+ * the common clock framework, when a corresponding of_clk_get call is
+ * executed, or recursively from itself when parsing parent clocks.
+ * Returns a pointer to the clock struct, or ERR_PTR value in failure.
+ */
+static struct clk *_sci_clk_get(struct sci_clk_provider *provider,
+				u16 dev_id, u8 clk_id, bool parse_parents)
+{
+	struct clk_init_data init = { NULL };
+	struct clk *clk;
+	struct sci_clk *sci_clk = NULL;
+	char name[20];
+	char **parent_names = NULL;
+	int i;
+	int ret;
+
+	list_for_each_entry(sci_clk, &provider->clocks, node)
+		if (sci_clk->dev_id == dev_id && sci_clk->clk_id == clk_id)
+			return sci_clk->hw.clk;
+
+	sci_clk = devm_kzalloc(provider->dev, sizeof(*sci_clk), GFP_KERNEL);
+	if (!sci_clk) {
+		ret = -ENOMEM;
+		goto err;
+	}
+
+	sci_clk->dev_id = dev_id;
+	sci_clk->clk_id = clk_id;
+	sci_clk->provider = provider;
+
+	if (parse_parents) {
+		ret = provider->ops->get_num_parents(provider->sci, dev_id,
+						     clk_id,
+						     &init.num_parents);
+		if (ret)
+			goto err;
+	}
+
+	snprintf(name, 20, "%s:%d:%d", dev_name(provider->dev), sci_clk->dev_id,
+		 sci_clk->clk_id);
+
+	init.name = name;
+
+	if (init.num_parents < 2)
+		init.num_parents = 0;
+
+	if (init.num_parents) {
+		parent_names = devm_kcalloc(provider->dev, init.num_parents,
+					    sizeof(char *), GFP_KERNEL);
+
+		if (!parent_names) {
+			ret = -ENOMEM;
+			goto err;
+		}
+
+		for (i = 0; i < init.num_parents; i++) {
+			char *parent_name;
+
+			parent_name = devm_kzalloc(provider->dev, 20,
+						   GFP_KERNEL);
+			if (!parent_name) {
+				ret = -ENOMEM;
+				goto err;
+			}
+			snprintf(parent_name, 20, "%s:%d:%d",
+				 dev_name(provider->dev), sci_clk->dev_id,
+				 sci_clk->clk_id + 1 + i);
+			parent_names[i] = parent_name;
+
+			_sci_clk_get(provider, dev_id, clk_id + 1 + i, false);
+		}
+		init.parent_names = (const char * const *)parent_names;
+	}
+
+	init.ops = &sci_clk_ops;
+	sci_clk->hw.init = &init;
+
+	clk = devm_clk_register(provider->dev, &sci_clk->hw);
+
+	if (IS_ERR(clk)) {
+		ret = PTR_ERR(clk);
+		dev_err(provider->dev, "failed clk register with %d\n", ret);
+		goto err;
+	} else {
+		list_add(&sci_clk->node, &provider->clocks);
+	}
+
+	return clk;
+
+err:
+	if (parent_names) {
+		for (i = 0; i < init.num_parents; i++)
+			devm_kfree(provider->dev, parent_names[i]);
+
+		devm_kfree(provider->dev, parent_names);
+	}
+
+	devm_kfree(provider->dev, sci_clk);
+
+	return ERR_PTR(ret);
+}
+
+/**
+ * sci_clk_get - Xlate function for getting clock handles
+ * @clkspec: device tree clock specifier
+ * @data: pointer to the clock provider
+ *
+ * Xlate function for retrieving clock TI SCI clock handles based on
+ * device tree clock specifier. Called from the common clock framework,
+ * when a corresponding of_clk_get call is executed. Returns a pointer
+ * to the TI SCI clock struct, or ERR_PTR value in failure.
+ */
+static struct clk *sci_clk_get(struct of_phandle_args *clkspec, void *data)
+{
+	struct sci_clk_provider *provider = data;
+	struct clk *clk;
+	u16 dev_id;
+	u8 clk_id;
+
+	if (clkspec->args_count != 2)
+		return ERR_PTR(-EINVAL);
+
+	mutex_lock(&provider->lock);
+
+	dev_id = clkspec->args[0];
+	clk_id = clkspec->args[1];
+
+	clk = _sci_clk_get(provider, dev_id, clk_id, true);
+
+	mutex_unlock(&provider->lock);
+
+	return clk;
+}
+
+static const struct of_device_id ti_sci_clk_of_match[] = {
+	{ .compatible = "ti,sci-clk" },
+	{ /* Sentinel */ },
+};
+MODULE_DEVICE_TABLE(of, ti_sci_clk_of_match);
+
+/**
+ * ti_sci_clk_parse_flags - Helper function to parse clock flag arrays
+ * @dev: clock provider device
+ * @np: device node pointer for the clock provider
+ * @list_name: property name containing the clocks list
+ * @flag: flag to apply to the list of clocks
+ *
+ * Parses a DT list based on the provided data, and applies the flag value
+ * for each of the clocks identified by the list. Return 0 for success,
+ * negative error value for failure.
+ */
+static int ti_sci_clk_parse_flags(struct device *dev, struct device_node *np,
+				  const char *list_name, u8 flag)
+{
+	int num_clks;
+	int i;
+
+	num_clks = of_count_phandle_with_args(np, list_name, "#clock-cells");
+
+	for (i = 0; i < num_clks; i++) {
+		struct of_phandle_args clkspec;
+		struct clk_hw *hw;
+		struct sci_clk *sci_clk;
+		struct clk *clk;
+		int ret;
+
+		ret = of_parse_phandle_with_args(np, list_name, "#clock-cells",
+						 i, &clkspec);
+		if (ret) {
+			dev_err(dev, "Failed to parse %s[%d] = %d\n", list_name,
+				i, ret);
+			return ret;
+		}
+		clk = of_clk_get_from_provider(&clkspec);
+		if (IS_ERR(clk)) {
+			dev_err(dev, "clk_get failed for %s[%d] = %ld\n",
+				list_name, i, PTR_ERR(clk));
+			return PTR_ERR(clk);
+		}
+		hw = __clk_get_hw(clk);
+		sci_clk = to_sci_clk(hw);
+
+		sci_clk->flags |= flag;
+	}
+
+	return 0;
+}
+
+/**
+ * ti_sci_clk_probe - Probe function for the TI SCI clock driver
+ * @pdev: platform device pointer to be probed
+ *
+ * Probes the TI SCI clock device. Allocates a new clock provider
+ * and registers this to the common clock framework. Also applies
+ * any required flags to the identified clocks via clock lists
+ * supplied from DT. Returns 0 for success, negative error value
+ * for failure.
+ */
+static int ti_sci_clk_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct device_node *np = dev->of_node;
+	struct sci_clk_provider *provider;
+	const struct ti_sci_handle *handle;
+
+	if (!np) {
+		dev_err(dev, "OF data missing\n");
+		return -EINVAL;
+	}
+
+	handle = devm_ti_sci_get_handle(dev);
+	if (IS_ERR(handle))
+		return PTR_ERR(handle);
+
+	provider = devm_kzalloc(dev, sizeof(*provider), GFP_KERNEL);
+	if (!provider)
+		return -ENOMEM;
+
+	INIT_LIST_HEAD(&provider->clocks);
+	mutex_init(&provider->lock);
+
+	provider->sci = handle;
+	provider->ops = &handle->ops.clk_ops;
+	provider->dev = dev;
+
+	of_clk_add_provider(np, sci_clk_get, provider);
+
+	ti_sci_clk_parse_flags(dev, np, "ti,ssc-clocks", SCI_CLK_SSC_ENABLE);
+	ti_sci_clk_parse_flags(dev, np, "ti,allow-freq-change-clocks",
+			       SCI_CLK_ALLOW_FREQ_CHANGE);
+	ti_sci_clk_parse_flags(dev, np, "ti,input-term-clocks",
+			       SCI_CLK_INPUT_TERMINATION);
+
+	dev_info(dev, "initialized.\n");
+
+	return 0;
+}
+
+/**
+ * ti_sci_clk_remove - Remove TI SCI clock device
+ * @pdev: platform device pointer for the device to be removed
+ *
+ * Removes the TI SCI device. Unregisters the clock provider registered
+ * via common clock framework. Any memory allocated for the device will
+ * be free'd silently via the devm framework. Returns 0 always.
+ */
+static int ti_sci_clk_remove(struct platform_device *pdev)
+{
+	of_clk_del_provider(pdev->dev.of_node);
+
+	return 0;
+}
+
+static struct platform_driver ti_sci_clk_driver = {
+	.probe = ti_sci_clk_probe,
+	.remove = ti_sci_clk_remove,
+	.driver = {
+		.name = "ti-sci-clk",
+		.of_match_table = of_match_ptr(ti_sci_clk_of_match),
+	},
+};
+module_platform_driver(ti_sci_clk_driver);
+
+MODULE_LICENSE("GPL v2");
+MODULE_DESCRIPTION("TI System Control Interface(SCI) Clock driver");
+MODULE_AUTHOR("Tero Kristo");
+MODULE_ALIAS("platform:ti-sci-clk");
-- 
2.9.1.200.gb1ec08f