clk: mvebu: new driver for Armada AP806 system controller

The Armada AP806 system controller, amongst other things, provides a
number of clocks for the platform: the CPU cluster clocks, whose
frequencies are found by reading the Sample At Reset register, one
fixed clock, and another clock derived from the fixed clock, which is
the one used by most peripherals in AP806.

The AP806 is one of the two core HW blocks used in the Marvell 7K/8K
SoCs.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
[sboyd@codeaurora.org: Silence some checkpatch noise]
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>

drivers/clk/mvebu/Kconfig

@@ -29,6 +29,9 @@ config ARMADA_XP_CLK
 	select MVEBU_CLK_COMMON
 	select MVEBU_CLK_CPU
 
+config ARMADA_AP806_SYSCON
+	bool
+
 config DOVE_CLK
 	bool
 	select MVEBU_CLK_COMMON

drivers/clk/mvebu/Makefile

@@ -7,6 +7,7 @@ obj-$(CONFIG_ARMADA_375_CLK)	+= armada-375.o
 obj-$(CONFIG_ARMADA_38X_CLK)	+= armada-38x.o
 obj-$(CONFIG_ARMADA_39X_CLK)	+= armada-39x.o
 obj-$(CONFIG_ARMADA_XP_CLK)	+= armada-xp.o
+obj-$(CONFIG_ARMADA_AP806_SYSCON) += ap806-system-controller.o
 obj-$(CONFIG_DOVE_CLK)		+= dove.o dove-divider.o
 obj-$(CONFIG_KIRKWOOD_CLK)	+= kirkwood.o
 obj-$(CONFIG_ORION_CLK)		+= orion.o

drivers/clk/mvebu/ap806-system-controller.c

@@ -0,0 +1,168 @@
+/*
+ * Marvell Armada AP806 System Controller
+ *
+ * Copyright (C) 2016 Marvell
+ *
+ * Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
+ *
+ * This file is licensed under the terms of the GNU General Public
+ * License version 2.  This program is licensed "as is" without any
+ * warranty of any kind, whether express or implied.
+ */
+
+#define pr_fmt(fmt) "ap806-system-controller: " fmt
+
+#include <linux/clk-provider.h>
+#include <linux/mfd/syscon.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/of_address.h>
+#include <linux/platform_device.h>
+#include <linux/regmap.h>
+
+#define AP806_SAR_REG			0x400
+#define AP806_SAR_CLKFREQ_MODE_MASK	0x1f
+
+#define AP806_CLK_NUM			4
+
+static struct clk *ap806_clks[AP806_CLK_NUM];
+
+static struct clk_onecell_data ap806_clk_data = {
+	.clks = ap806_clks,
+	.clk_num = AP806_CLK_NUM,
+};
+
+static int ap806_syscon_clk_probe(struct platform_device *pdev)
+{
+	unsigned int freq_mode, cpuclk_freq;
+	const char *name, *fixedclk_name;
+	struct device_node *np = pdev->dev.of_node;
+	struct regmap *regmap;
+	u32 reg;
+	int ret;
+
+	regmap = syscon_node_to_regmap(np);
+	if (IS_ERR(regmap)) {
+		dev_err(&pdev->dev, "cannot get regmap\n");
+		return PTR_ERR(regmap);
+	}
+
+	ret = regmap_read(regmap, AP806_SAR_REG, &reg);
+	if (ret) {
+		dev_err(&pdev->dev, "cannot read from regmap\n");
+		return ret;
+	}
+
+	freq_mode = reg & AP806_SAR_CLKFREQ_MODE_MASK;
+	switch (freq_mode) {
+	case 0x0 ... 0x5:
+		cpuclk_freq = 2000;
+		break;
+	case 0x6 ... 0xB:
+		cpuclk_freq = 1800;
+		break;
+	case 0xC ... 0x11:
+		cpuclk_freq = 1600;
+		break;
+	case 0x12 ... 0x16:
+		cpuclk_freq = 1400;
+		break;
+	case 0x17 ... 0x19:
+		cpuclk_freq = 1300;
+		break;
+	default:
+		dev_err(&pdev->dev, "invalid SAR value\n");
+		return -EINVAL;
+	}
+
+	/* Convert to hertz */
+	cpuclk_freq *= 1000 * 1000;
+
+	/* CPU clocks depend on the Sample At Reset configuration */
+	of_property_read_string_index(np, "clock-output-names",
+				      0, &name);
+	ap806_clks[0] = clk_register_fixed_rate(&pdev->dev, name, NULL,
+						0, cpuclk_freq);
+	if (IS_ERR(ap806_clks[0])) {
+		ret = PTR_ERR(ap806_clks[0]);
+		goto fail0;
+	}
+
+	of_property_read_string_index(np, "clock-output-names",
+				      1, &name);
+	ap806_clks[1] = clk_register_fixed_rate(&pdev->dev, name, NULL, 0,
+						cpuclk_freq);
+	if (IS_ERR(ap806_clks[1])) {
+		ret = PTR_ERR(ap806_clks[1]);
+		goto fail1;
+	}
+
+	/* Fixed clock is always 1200 Mhz */
+	of_property_read_string_index(np, "clock-output-names",
+				      2, &fixedclk_name);
+	ap806_clks[2] = clk_register_fixed_rate(&pdev->dev, fixedclk_name, NULL,
+						0, 1200 * 1000 * 1000);
+	if (IS_ERR(ap806_clks[2])) {
+		ret = PTR_ERR(ap806_clks[2]);
+		goto fail2;
+	}
+
+	/* MSS Clock is fixed clock divided by 6 */
+	of_property_read_string_index(np, "clock-output-names",
+				      3, &name);
+	ap806_clks[3] = clk_register_fixed_factor(NULL, name, fixedclk_name,
+						  0, 1, 6);
+	if (IS_ERR(ap806_clks[3])) {
+		ret = PTR_ERR(ap806_clks[3]);
+		goto fail3;
+	}
+
+	ret = of_clk_add_provider(np, of_clk_src_onecell_get, &ap806_clk_data);
+	if (ret)
+		goto fail_clk_add;
+
+	return 0;
+
+fail_clk_add:
+	clk_unregister_fixed_factor(ap806_clks[3]);
+fail3:
+	clk_unregister_fixed_rate(ap806_clks[2]);
+fail2:
+	clk_unregister_fixed_rate(ap806_clks[1]);
+fail1:
+	clk_unregister_fixed_rate(ap806_clks[0]);
+fail0:
+	return ret;
+}
+
+static int ap806_syscon_clk_remove(struct platform_device *pdev)
+{
+	of_clk_del_provider(pdev->dev.of_node);
+	clk_unregister_fixed_factor(ap806_clks[3]);
+	clk_unregister_fixed_rate(ap806_clks[2]);
+	clk_unregister_fixed_rate(ap806_clks[1]);
+	clk_unregister_fixed_rate(ap806_clks[0]);
+
+	return 0;
+}
+
+static const struct of_device_id ap806_syscon_of_match[] = {
+	{ .compatible = "marvell,ap806-system-controller", },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, armada8k_pcie_of_match);
+
+static struct platform_driver ap806_syscon_driver = {
+	.probe = ap806_syscon_clk_probe,
+	.remove = ap806_syscon_clk_remove,
+	.driver		= {
+		.name	= "marvell-ap806-system-controller",
+		.of_match_table = ap806_syscon_of_match,
+	},
+};
+
+module_platform_driver(ap806_syscon_driver);
+
+MODULE_DESCRIPTION("Marvell AP806 System Controller driver");
+MODULE_AUTHOR("Thomas Petazzoni <thomas.petazzoni@free-electrons.com>");
+MODULE_LICENSE("GPL");