clk: keystone: Add gate control clock driver

Add the driver for the clock gate control which uses PSC (Power Sleep
Controller) IP on Keystone 2 based SOCs. It is responsible for enabling and
disabling of the clocks for different IPs present in the SoC.

Signed-off-by: Santosh Shilimkar <[e-mail]>
Signed-off-by: Mike Turquette <[e-mail]>

Documentation/devicetree/bindings/clock/keystone-gate.txt

···
+Status: Unstable - ABI compatibility may be broken in the future
+
+Binding for Keystone gate control driver which uses PSC controller IP.
+
+This binding uses the common clock binding[1].
+
+[1] Documentation/devicetree/bindings/clock/clock-bindings.txt
+
+Required properties:
+- compatible : shall be "ti,keystone,psc-clock".
+- #clock-cells : from common clock binding; shall be set to 0.
+- clocks : parent clock phandle
+- reg :	psc control and domain address address space
+- reg-names : psc control and domain registers
+- domain-id : psc domain id needed to check the transition state register
+
+Optional properties:
+- clock-output-names : From common clock binding to override the
+			default output clock name
+Example:
+	clkusb: clkusb {
+		#clock-cells = <0>;
+		compatible = "ti,keystone,psc-clock";
+		clocks = <&chipclk16>;
+		clock-output-names = "usb";
+		reg = <0x02350008 0xb00>, <0x02350000 0x400>;
+		reg-names = "control", "domain";
+		domain-id = <0>;
+	};

drivers/clk/keystone/gate.c

···
+/*
+ * Clock driver for Keystone 2 based devices
+ *
+ * Copyright (C) 2013 Texas Instruments.
+ *	Murali Karicheri <[e-mail]>
+ *	Santosh Shilimkar <[e-mail]>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ */
+#include <linux/clk.h>
+#include <linux/clk-provider.h>
+#include <linux/err.h>
+#include <linux/io.h>
+#include <linux/slab.h>
+#include <linux/of_address.h>
+#include <linux/of.h>
+#include <linux/module.h>
+
+/* PSC register offsets */
+#define PTCMD			0x120
+#define PTSTAT			0x128
+#define PDSTAT			0x200
+#define PDCTL			0x300
+#define MDSTAT			0x800
+#define MDCTL			0xa00
+
+/* PSC module states */
+#define PSC_STATE_SWRSTDISABLE	0
+#define PSC_STATE_SYNCRST	1
+#define PSC_STATE_DISABLE	2
+#define PSC_STATE_ENABLE	3
+
+#define MDSTAT_STATE_MASK	0x3f
+#define MDSTAT_MCKOUT		BIT(12)
+#define PDSTAT_STATE_MASK	0x1f
+#define MDCTL_FORCE		BIT(31)
+#define MDCTL_LRESET		BIT(8)
+#define PDCTL_NEXT		BIT(0)
+
+/* Maximum timeout to bail out state transition for module */
+#define STATE_TRANS_MAX_COUNT	0xffff
+
+static void __iomem *domain_transition_base;
+
+/**
+ * struct clk_psc_data - PSC data
+ * @control_base: Base address for a PSC control
+ * @domain_base: Base address for a PSC domain
+ * @domain_id: PSC domain id number
+ */
+struct clk_psc_data {
+	void __iomem *control_base;
+	void __iomem *domain_base;
+	u32 domain_id;
+};
+
+/**
+ * struct clk_psc - PSC clock structure
+ * @hw: clk_hw for the psc
+ * @psc_data: PSC driver specific data
+ * @lock: Spinlock used by the driver
+ */
+struct clk_psc {
+	struct clk_hw hw;
+	struct clk_psc_data *psc_data;
+	spinlock_t *lock;
+};
+
+static DEFINE_SPINLOCK(psc_lock);
+
+#define to_clk_psc(_hw) container_of(_hw, struct clk_psc, hw)
+
+static void psc_config(void __iomem *control_base, void __iomem *domain_base,
+						u32 next_state, u32 domain_id)
+{
+	u32 ptcmd, pdstat, pdctl, mdstat, mdctl, ptstat;
+	u32 count = STATE_TRANS_MAX_COUNT;
+
+	mdctl = readl(control_base + MDCTL);
+	mdctl &= ~MDSTAT_STATE_MASK;
+	mdctl |= next_state;
+	/* For disable, we always put the module in local reset */
+	if (next_state == PSC_STATE_DISABLE)
+		mdctl &= ~MDCTL_LRESET;
+	writel(mdctl, control_base + MDCTL);
+
+	pdstat = readl(domain_base + PDSTAT);
+	if (!(pdstat & PDSTAT_STATE_MASK)) {
+		pdctl = readl(domain_base + PDCTL);
+		pdctl |= PDCTL_NEXT;
+		writel(pdctl, domain_base + PDCTL);
+	}
+
+	ptcmd = 1 << domain_id;
+	writel(ptcmd, domain_transition_base + PTCMD);
+	do {
+		ptstat = readl(domain_transition_base + PTSTAT);
+	} while (((ptstat >> domain_id) & 1) && count--);
+
+	count = STATE_TRANS_MAX_COUNT;
+	do {
+		mdstat = readl(control_base + MDSTAT);
+	} while (!((mdstat & MDSTAT_STATE_MASK) == next_state) && count--);
+}
+
+static int keystone_clk_is_enabled(struct clk_hw *hw)
+{
+	struct clk_psc *psc = to_clk_psc(hw);
+	struct clk_psc_data *data = psc->psc_data;
+	u32 mdstat = readl(data->control_base + MDSTAT);
+
+	return (mdstat & MDSTAT_MCKOUT) ? 1 : 0;
+}
+
+static int keystone_clk_enable(struct clk_hw *hw)
+{
+	struct clk_psc *psc = to_clk_psc(hw);
+	struct clk_psc_data *data = psc->psc_data;
+	unsigned long flags = 0;
+
+	if (psc->lock)
+		spin_lock_irqsave(psc->lock, flags);
+
+	psc_config(data->control_base, data->domain_base,
+				PSC_STATE_ENABLE, data->domain_id);
+
+	if (psc->lock)
+		spin_unlock_irqrestore(psc->lock, flags);
+
+	return 0;
+}
+
+static void keystone_clk_disable(struct clk_hw *hw)
+{
+	struct clk_psc *psc = to_clk_psc(hw);
+	struct clk_psc_data *data = psc->psc_data;
+	unsigned long flags = 0;
+
+	if (psc->lock)
+		spin_lock_irqsave(psc->lock, flags);
+
+	psc_config(data->control_base, data->domain_base,
+				PSC_STATE_DISABLE, data->domain_id);
+
+	if (psc->lock)
+		spin_unlock_irqrestore(psc->lock, flags);
+}
+
+static const struct clk_ops clk_psc_ops = {
+	.enable = keystone_clk_enable,
+	.disable = keystone_clk_disable,
+	.is_enabled = keystone_clk_is_enabled,
+};
+
+/**
+ * clk_register_psc - register psc clock
+ * @dev: device that is registering this clock
+ * @name: name of this clock
+ * @parent_name: name of clock's parent
+ * @psc_data: platform data to configure this clock
+ * @lock: spinlock used by this clock
+ */
+static struct clk *clk_register_psc(struct device *dev,
+			const char *name,
+			const char *parent_name,
+			struct clk_psc_data *psc_data,
+			spinlock_t *lock)
+{
+	struct clk_init_data init;
+	struct clk_psc *psc;
+	struct clk *clk;
+
+	psc = kzalloc(sizeof(*psc), GFP_KERNEL);
+	if (!psc)
+		return ERR_PTR(-ENOMEM);
+
+	init.name = name;
+	init.ops = &clk_psc_ops;
+	init.parent_names = (parent_name ? &parent_name : NULL);
+	init.num_parents = (parent_name ? 1 : 0);
+
+	psc->psc_data = psc_data;
+	psc->lock = lock;
+	psc->hw.init = &init;
+
+	clk = clk_register(NULL, &psc->hw);
+	if (IS_ERR(clk))
+		kfree(psc);
+
+	return clk;
+}
+
+/**
+ * of_psc_clk_init - initialize psc clock through DT
+ * @node: device tree node for this clock
+ * @lock: spinlock used by this clock
+ */
+static void __init of_psc_clk_init(struct device_node *node, spinlock_t *lock)
+{
+	const char *clk_name = node->name;
+	const char *parent_name;
+	struct clk_psc_data *data;
+	struct clk *clk;
+	int i;
+
+	data = kzalloc(sizeof(*data), GFP_KERNEL);
+	if (!data) {
+		pr_err("%s: Out of memory\n", __func__);
+		return;
+	}
+
+	i = of_property_match_string(node, "reg-names", "control");
+	data->control_base = of_iomap(node, i);
+	if (!data->control_base) {
+		pr_err("%s: control ioremap failed\n", __func__);
+		goto out;
+	}
+
+	i = of_property_match_string(node, "reg-names", "domain");
+	data->domain_base = of_iomap(node, i);
+	if (!data->domain_base) {
+		pr_err("%s: domain ioremap failed\n", __func__);
+		iounmap(data->control_base);
+		goto out;
+	}
+
+	of_property_read_u32(node, "domain-id", &data->domain_id);
+
+	/* Domain transition registers at fixed address space of domain_id 0 */
+	if (!domain_transition_base && !data->domain_id)
+		domain_transition_base = data->domain_base;
+
+	of_property_read_string(node, "clock-output-names", &clk_name);
+	parent_name = of_clk_get_parent_name(node, 0);
+	if (!parent_name) {
+		pr_err("%s: Parent clock not found\n", __func__);
+		goto out;
+	}
+
+	clk = clk_register_psc(NULL, clk_name, parent_name, data, lock);
+	if (clk) {
+		of_clk_add_provider(node, of_clk_src_simple_get, clk);
+		return;
+	}
+
+	pr_err("%s: error registering clk %s\n", __func__, node->name);
+out:
+	kfree(data);
+	return;
+}
+
+/**
+ * of_keystone_psc_clk_init - initialize psc clock through DT
+ * @node: device tree node for this clock
+ */
+static void __init of_keystone_psc_clk_init(struct device_node *node)
+{
+	of_psc_clk_init(node, &psc_lock);
+}
+CLK_OF_DECLARE(keystone_gate_clk, "ti,keystone,psc-clock",
+					of_keystone_psc_clk_init);