clk: add support for clocks provided by system control processor

On some ARM based systems, a separate Cortex-M based System Control
Processor(SCP) provides the overall power, clock, reset and system
control. System Control and Power Interface(SCPI) Message Protocol
is defined for the communication between the Application Cores(AP)
and the SCP.

This patch adds support for the clocks provided by SCP using SCPI
protocol.

Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
Signed-off-by: Jon Medhurst <tixy@linaro.org>

4 files changed, 354 insertions, 0 deletions

diff --git a/Documentation/devicetree/bindings/clock/scpi.txt b/Documentation/devicetree/bindings/clock/scpi.txt
new file mode 100644
index 000000000000..b2b7035018f4
--- /dev/null
+++ b/Documentation/devicetree/bindings/clock/scpi.txt
@@ -0,0 +1,34 @@
+Device Tree Clock bindings for the clocks based on
+System Control and Power Interface (SCPI) Message Protocol
+
+This binding uses the common clock binding[1].
+
+Required properties:
+- compatible : shall be one of the following:
+	"arm,scpi-clks" - for the container node with all the clocks
+		based on the SCPI protocol
+	"arm,scpi-clk-indexed" - all the clocks that are variable and index
+		based. These clocks don't provide the full range between the
+		limits but only discrete points within the range. The firmware
+		provides the mapping for each such operating frequency and the
+		index associated with it.
+	"arm,scpi-clk-range" - all the clocks that are variable and provide
+		full range within the specified range
+
+Required properties for all clocks(all from common clock binding):
+- #clock-cells : ; shall be set to 0 or 1 depending on whether it has single
+	or multiple clock outputs.
+- clock-output-names : shall be the corresponding names of the outputs.
+- clock-indices: The identifyng number for the clocks in the node as expected
+	by the firmware. It can be non linear and hence provide the mapping
+	of identifiers into the clock-output-names array.
+- frequency-range: The allowed range of clock frequency supported specified
+	in the form of minimum and maximum limits(two u32 fields)
+	This is required only if compatible is "arm,scpi-clk-range"
+
+Clock consumers should specify the desired clocks they use with a
+"clocks" phandle cell. Consumers should also provide an additional ID
+in their clock property. This ID refers to the specific clock in the clock
+provider list.
+
+[1] Documentation/devicetree/bindings/clock/clock-bindings.txt
diff --git a/drivers/clk/Kconfig b/drivers/clk/Kconfig
index 0b474a04730f..53f622291abb 100644
--- a/drivers/clk/Kconfig
+++ b/drivers/clk/Kconfig
@@ -33,6 +33,16 @@ config COMMON_CLK_WM831X
 
 source "drivers/clk/versatile/Kconfig"
 
+config COMMON_CLK_SCPI
+        bool "Clock driver controlled via SCPI interface"
+        depends on ARM_SCPI_PROTOCOL
+        ---help---
+          This driver provides support for clocks that are controlled
+          by firmware that implements the SCPI interface.
+
+	  This driver uses SCPI Message Protocol to interact with the
+	  firware providing all the clock controls.
+
 config COMMON_CLK_MAX_GEN
         bool
 
diff --git a/drivers/clk/Makefile b/drivers/clk/Makefile
index d478ceb69c5f..610571bd66d5 100644
--- a/drivers/clk/Makefile
+++ b/drivers/clk/Makefile
@@ -35,6 +35,7 @@ obj-$(CONFIG_COMMON_CLK_PALMAS)		+= clk-palmas.o
 obj-$(CONFIG_CLK_QORIQ)			+= clk-qoriq.o
 obj-$(CONFIG_COMMON_CLK_RK808)		+= clk-rk808.o
 obj-$(CONFIG_COMMON_CLK_S2MPS11)	+= clk-s2mps11.o
+obj-$(CONFIG_COMMON_CLK_SCPI)           += clk-scpi.o
 obj-$(CONFIG_COMMON_CLK_SI5351)		+= clk-si5351.o
 obj-$(CONFIG_COMMON_CLK_SI570)		+= clk-si570.o
 obj-$(CONFIG_CLK_TWL6040)		+= clk-twl6040.o
diff --git a/drivers/clk/clk-scpi.c b/drivers/clk/clk-scpi.c
new file mode 100644
index 000000000000..2d707663542f
--- /dev/null
+++ b/drivers/clk/clk-scpi.c
@@ -0,0 +1,309 @@
+/*
+ * System Control and Power Interface (SCPI) Protocol based clock driver
+ *
+ * Copyright (C) 2014 ARM Ltd.
+ *
+ * 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/clkdev.h>
+#include <linux/clk-provider.h>
+#include <linux/device.h>
+#include <linux/err.h>
+#include <linux/of.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/scpi_protocol.h>
+
+struct scpi_clk {
+	u32 id;
+	const char *name;
+	struct clk_hw hw;
+	struct scpi_opp *opps;
+	unsigned long rate_min;
+	unsigned long rate_max;
+};
+
+#define to_scpi_clk(clk) container_of(clk, struct scpi_clk, hw)
+
+static unsigned long scpi_clk_recalc_rate(struct clk_hw *hw,
+					  unsigned long parent_rate)
+{
+	struct scpi_clk *clk = to_scpi_clk(hw);
+	return scpi_clk_get_val(clk->id);
+}
+
+static long scpi_clk_round_rate(struct clk_hw *hw, unsigned long rate,
+				unsigned long *parent_rate)
+{
+	struct scpi_clk *clk = to_scpi_clk(hw);
+	if (clk->rate_min && rate < clk->rate_min)
+		rate = clk->rate_min;
+	if (clk->rate_max && rate > clk->rate_max)
+		rate = clk->rate_max;
+
+	return rate;
+}
+
+static int scpi_clk_set_rate(struct clk_hw *hw, unsigned long rate,
+			     unsigned long parent_rate)
+{
+	struct scpi_clk *clk = to_scpi_clk(hw);
+	return scpi_clk_set_val(clk->id, rate);
+}
+
+static struct clk_ops scpi_clk_ops = {
+	.recalc_rate = scpi_clk_recalc_rate,
+	.round_rate = scpi_clk_round_rate,
+	.set_rate = scpi_clk_set_rate,
+};
+
+/* find closest match to given frequency in OPP table */
+static int __scpi_dvfs_round_rate(struct scpi_clk *clk, unsigned long rate)
+{
+	int idx, max_opp = clk->opps->count;
+	u32 *freqs = clk->opps->freqs;
+	u32 fmin = 0, fmax = ~0, ftmp;
+
+	for (idx = 0; idx < max_opp; idx++, freqs++) {
+		ftmp = *freqs;
+		if (ftmp >= (u32)rate) {
+			if (ftmp <= fmax)
+				fmax = ftmp;
+		} else {
+			if (ftmp >= fmin)
+				fmin = ftmp;
+		}
+	}
+	if (fmax != ~0)
+		return fmax;
+	else
+		return fmin;
+}
+
+static unsigned long scpi_dvfs_recalc_rate(struct clk_hw *hw,
+					   unsigned long parent_rate)
+{
+	struct scpi_clk *clk = to_scpi_clk(hw);
+	int idx = scpi_dvfs_get_idx(clk->id);
+	u32 *freqs = clk->opps->freqs;
+
+	if (idx < 0)
+		return 0;
+	else
+		return *(freqs + idx);
+}
+
+static long scpi_dvfs_round_rate(struct clk_hw *hw, unsigned long rate,
+				 unsigned long *parent_rate)
+{
+	struct scpi_clk *clk = to_scpi_clk(hw);
+	return __scpi_dvfs_round_rate(clk, rate);
+}
+
+static int __scpi_find_dvfs_index(struct scpi_clk *clk, unsigned long rate)
+{
+	int idx, max_opp = clk->opps->count;
+	u32 *freqs = clk->opps->freqs;
+
+	for (idx = 0; idx < max_opp; idx++, freqs++)
+		if (*freqs == (u32)rate)
+			break;
+	return (idx == max_opp) ? -EINVAL : idx;
+}
+
+static int scpi_dvfs_set_rate(struct clk_hw *hw, unsigned long rate,
+			      unsigned long parent_rate)
+{
+	struct scpi_clk *clk = to_scpi_clk(hw);
+	int ret = __scpi_find_dvfs_index(clk, rate);
+
+	if (ret < 0)
+		return ret;
+	else
+		return scpi_dvfs_set_idx(clk->id, (u8)ret);
+}
+
+static struct clk_ops scpi_dvfs_ops = {
+	.recalc_rate = scpi_dvfs_recalc_rate,
+	.round_rate = scpi_dvfs_round_rate,
+	.set_rate = scpi_dvfs_set_rate,
+};
+
+static struct clk *
+scpi_dvfs_ops_init(struct device *dev, struct device_node *np,
+		   struct scpi_clk *sclk)
+{
+	struct clk_init_data init;
+	struct scpi_opp *opp;
+
+	init.name = sclk->name;
+	init.flags = CLK_IS_ROOT;
+	init.num_parents = 0;
+	init.ops = &scpi_dvfs_ops;
+	sclk->hw.init = &init;
+
+	opp = scpi_dvfs_get_opps(sclk->id);
+	if (IS_ERR(opp))
+		return (struct clk *)opp;
+
+	sclk->opps = opp;
+
+	return devm_clk_register(dev, &sclk->hw);
+}
+
+static struct clk *
+scpi_clk_ops_init(struct device *dev, struct device_node *np,
+		  struct scpi_clk *sclk)
+{
+	struct clk_init_data init;
+	u32 range[2];
+	int ret;
+
+	init.name = sclk->name;
+	init.flags = CLK_IS_ROOT;
+	init.num_parents = 0;
+	init.ops = &scpi_clk_ops;
+	sclk->hw.init = &init;
+
+	ret = of_property_read_u32_array(np, "frequency-range", range,
+					 ARRAY_SIZE(range));
+	if (ret)
+		return ERR_PTR(ret);
+	sclk->rate_min = range[0];
+	sclk->rate_max = range[1];
+
+	return devm_clk_register(dev, &sclk->hw);
+}
+
+static int scpi_clk_setup(struct device *dev, struct device_node *np,
+			  const void *data)
+{
+	struct clk *(*setup_ops)(struct device *, struct device_node *,
+				 struct scpi_clk *) = data;
+	struct clk_onecell_data *clk_data;
+	struct clk **clks;
+	size_t count;
+	int idx;
+
+	count = of_property_count_strings(np, "clock-output-names");
+	if (count < 0) {
+		dev_err(dev, "%s: invalid clock output count\n", np->name);
+		return -EINVAL;
+	}
+
+	clk_data = devm_kmalloc(dev, sizeof(*clk_data), GFP_KERNEL);
+	if (!clk_data) {
+		dev_err(dev, "failed to allocate clock provider data\n");
+		return -ENOMEM;
+	}
+
+	clks = devm_kmalloc(dev, count * sizeof(*clks), GFP_KERNEL);
+	if (!clks) {
+		dev_err(dev, "failed to allocate clock providers\n");
+		return -ENOMEM;
+	}
+
+	for (idx = 0; idx < count; idx++) {
+		struct scpi_clk *sclk;
+		u32 val;
+
+		sclk = devm_kzalloc(dev, sizeof(*sclk), GFP_KERNEL);
+		if (!sclk) {
+			dev_err(dev, "failed to allocate scpi clocks\n");
+			return -ENOMEM;
+		}
+
+		if (of_property_read_string_index(np, "clock-output-names",
+						  idx, &sclk->name)) {
+			dev_err(dev, "invalid clock name @ %s\n", np->name);
+			return -EINVAL;
+		}
+
+		if (of_property_read_u32_index(np, "clock-indices",
+					       idx, &val)) {
+			dev_err(dev, "invalid clock index @ %s\n", np->name);
+			return -EINVAL;
+		}
+
+		sclk->id = val;
+
+		clks[idx] = setup_ops(dev, np, sclk);
+		if (IS_ERR(clks[idx])) {
+			dev_err(dev, "failed to register clock '%s'\n",
+				sclk->name);
+			return PTR_ERR(clks[idx]);
+		}
+
+		dev_dbg(dev, "Registered clock '%s'\n", sclk->name);
+	}
+
+	clk_data->clks = clks;
+	clk_data->clk_num = count;
+	of_clk_add_provider(np, of_clk_src_onecell_get, clk_data);
+
+	return 0;
+}
+
+static const struct of_device_id clk_match[] = {
+	{ .compatible = "arm,scpi-clk-indexed", .data = scpi_dvfs_ops_init, },
+	{ .compatible = "arm,scpi-clk-range", .data = &scpi_clk_ops_init, },
+	{}
+};
+
+static int scpi_clk_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct device_node *np = dev->of_node, *child;
+	const struct of_device_id *match;
+	int ret;
+
+	for_each_child_of_node(np, child) {
+		match = of_match_node(clk_match, child);
+		if (!match)
+			continue;
+		ret = scpi_clk_setup(dev, child, match->data);
+		if (ret)
+			return ret;
+	}
+	return 0;
+}
+
+static struct of_device_id scpi_clk_ids[] = {
+	{ .compatible = "arm,scpi-clks", },
+	{}
+};
+
+static struct platform_driver scpi_clk_driver = {
+	.driver	= {
+		.name = "scpi_clocks",
+		.of_match_table = scpi_clk_ids,
+	},
+	.probe = scpi_clk_probe,
+};
+
+static int __init scpi_clk_init(void)
+{
+	return platform_driver_register(&scpi_clk_driver);
+}
+postcore_initcall(scpi_clk_init);
+
+static void __exit scpi_clk_exit(void)
+{
+	platform_driver_unregister(&scpi_clk_driver);
+}
+module_exit(scpi_clk_exit);
+
+MODULE_AUTHOR("Sudeep Holla <sudeep.holla@arm.com>");
+MODULE_DESCRIPTION("ARM SCPI clock driver");
+MODULE_LICENSE("GPL");