clk: x86: Add Atom PMC platform clocks

The BayTrail and CherryTrail platforms provide platform clocks
through their Power Management Controller (PMC).

The SoC supports up to 6 clocks (PMC_PLT_CLK[0..5]) with a
frequency of either 19.2 MHz (PLL) or 25 MHz (XTAL) for BayTrail
and a frequency of 19.2 MHz (XTAL) for CherryTrail. These clocks
are available for general system use, where appropriate, and each
have Control & Frequency register fields associated with them.

Port from legacy by Pierre Bossart, integration in clock framework
by Irina Tirdea

Signed-off-by: Irina Tirdea <[e-mail]>
Signed-off-by: Pierre-Louis Bossart <[e-mail]>
Acked-by: Andy Shevchenko <[e-mail]>
Signed-off-by: Stephen Boyd <[e-mail]>

drivers/clk/x86/Makefile

···
 clk-x86-lpss-objs		:= clk-lpt.o
 obj-$(CONFIG_X86_INTEL_LPSS)	+= clk-x86-lpss.o
+obj-$(CONFIG_PMC_ATOM)		+= clk-pmc-atom.o

drivers/clk/x86/clk-pmc-atom.c

···
+/*
+ * Intel Atom platform clocks driver for BayTrail and CherryTrail SoCs
+ *
+ * Copyright (C) 2016, Intel Corporation
+ * Author: Irina Tirdea <[e-mail]>
+ *
+ * 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.
+ */
+
+#include <linux/clk-provider.h>
+#include <linux/clkdev.h>
+#include <linux/err.h>
+#include <linux/platform_data/x86/clk-pmc-atom.h>
+#include <linux/platform_device.h>
+#include <linux/slab.h>
+
+#define PLT_CLK_NAME_BASE	"pmc_plt_clk"
+
+#define PMC_CLK_CTL_OFFSET		0x60
+#define PMC_CLK_CTL_SIZE		4
+#define PMC_CLK_NUM			6
+#define PMC_CLK_CTL_GATED_ON_D3		0x0
+#define PMC_CLK_CTL_FORCE_ON		0x1
+#define PMC_CLK_CTL_FORCE_OFF		0x2
+#define PMC_CLK_CTL_RESERVED		0x3
+#define PMC_MASK_CLK_CTL		GENMASK(1, 0)
+#define PMC_MASK_CLK_FREQ		BIT(2)
+#define PMC_CLK_FREQ_XTAL		(0 << 2)	/* 25 MHz */
+#define PMC_CLK_FREQ_PLL		(1 << 2)	/* 19.2 MHz */
+
+struct clk_plt_fixed {
+	struct clk_hw *clk;
+	struct clk_lookup *lookup;
+};
+
+struct clk_plt {
+	struct clk_hw hw;
+	void __iomem *reg;
+	struct clk_lookup *lookup;
+	/* protect access to PMC registers */
+	spinlock_t lock;
+};
+
+#define to_clk_plt(_hw) container_of(_hw, struct clk_plt, hw)
+
+struct clk_plt_data {
+	struct clk_plt_fixed **parents;
+	u8 nparents;
+	struct clk_plt *clks[PMC_CLK_NUM];
+};
+
+/* Return an index in parent table */
+static inline int plt_reg_to_parent(int reg)
+{
+	switch (reg & PMC_MASK_CLK_FREQ) {
+	default:
+	case PMC_CLK_FREQ_XTAL:
+		return 0;
+	case PMC_CLK_FREQ_PLL:
+		return 1;
+	}
+}
+
+/* Return clk index of parent */
+static inline int plt_parent_to_reg(int index)
+{
+	switch (index) {
+	default:
+	case 0:
+		return PMC_CLK_FREQ_XTAL;
+	case 1:
+		return PMC_CLK_FREQ_PLL;
+	}
+}
+
+/* Abstract status in simpler enabled/disabled value */
+static inline int plt_reg_to_enabled(int reg)
+{
+	switch (reg & PMC_MASK_CLK_CTL) {
+	case PMC_CLK_CTL_GATED_ON_D3:
+	case PMC_CLK_CTL_FORCE_ON:
+		return 1;	/* enabled */
+	case PMC_CLK_CTL_FORCE_OFF:
+	case PMC_CLK_CTL_RESERVED:
+	default:
+		return 0;	/* disabled */
+	}
+}
+
+static void plt_clk_reg_update(struct clk_plt *clk, u32 mask, u32 val)
+{
+	u32 tmp;
+	unsigned long flags;
+
+	spin_lock_irqsave(&clk->lock, flags);
+
+	tmp = readl(clk->reg);
+	tmp = (tmp & ~mask) | (val & mask);
+	writel(tmp, clk->reg);
+
+	spin_unlock_irqrestore(&clk->lock, flags);
+}
+
+static int plt_clk_set_parent(struct clk_hw *hw, u8 index)
+{
+	struct clk_plt *clk = to_clk_plt(hw);
+
+	plt_clk_reg_update(clk, PMC_MASK_CLK_FREQ, plt_parent_to_reg(index));
+
+	return 0;
+}
+
+static u8 plt_clk_get_parent(struct clk_hw *hw)
+{
+	struct clk_plt *clk = to_clk_plt(hw);
+	u32 value;
+
+	value = readl(clk->reg);
+
+	return plt_reg_to_parent(value);
+}
+
+static int plt_clk_enable(struct clk_hw *hw)
+{
+	struct clk_plt *clk = to_clk_plt(hw);
+
+	plt_clk_reg_update(clk, PMC_MASK_CLK_CTL, PMC_CLK_CTL_FORCE_ON);
+
+	return 0;
+}
+
+static void plt_clk_disable(struct clk_hw *hw)
+{
+	struct clk_plt *clk = to_clk_plt(hw);
+
+	plt_clk_reg_update(clk, PMC_MASK_CLK_CTL, PMC_CLK_CTL_FORCE_OFF);
+}
+
+static int plt_clk_is_enabled(struct clk_hw *hw)
+{
+	struct clk_plt *clk = to_clk_plt(hw);
+	u32 value;
+
+	value = readl(clk->reg);
+
+	return plt_reg_to_enabled(value);
+}
+
+static const struct clk_ops plt_clk_ops = {
+	.enable = plt_clk_enable,
+	.disable = plt_clk_disable,
+	.is_enabled = plt_clk_is_enabled,
+	.get_parent = plt_clk_get_parent,
+	.set_parent = plt_clk_set_parent,
+	.determine_rate = __clk_mux_determine_rate,
+};
+
+static struct clk_plt *plt_clk_register(struct platform_device *pdev, int id,
+					void __iomem *base,
+					const char **parent_names,
+					int num_parents)
+{
+	struct clk_plt *pclk;
+	struct clk_init_data init;
+	int ret;
+
+	pclk = devm_kzalloc(&pdev->dev, sizeof(*pclk), GFP_KERNEL);
+	if (!pclk)
+		return ERR_PTR(-ENOMEM);
+
+	init.name =  kasprintf(GFP_KERNEL, "%s_%d", PLT_CLK_NAME_BASE, id);
+	init.ops = &plt_clk_ops;
+	init.flags = 0;
+	init.parent_names = parent_names;
+	init.num_parents = num_parents;
+
+	pclk->hw.init = &init;
+	pclk->reg = base + PMC_CLK_CTL_OFFSET + id * PMC_CLK_CTL_SIZE;
+	spin_lock_init(&pclk->lock);
+
+	ret = devm_clk_hw_register(&pdev->dev, &pclk->hw);
+	if (ret) {
+		pclk = ERR_PTR(ret);
+		goto err_free_init;
+	}
+
+	pclk->lookup = clkdev_hw_create(&pclk->hw, init.name, NULL);
+	if (!pclk->lookup) {
+		pclk = ERR_PTR(-ENOMEM);
+		goto err_free_init;
+	}
+
+err_free_init:
+	kfree(init.name);
+	return pclk;
+}
+
+static void plt_clk_unregister(struct clk_plt *pclk)
+{
+	clkdev_drop(pclk->lookup);
+}
+
+static struct clk_plt_fixed *plt_clk_register_fixed_rate(struct platform_device *pdev,
+						 const char *name,
+						 const char *parent_name,
+						 unsigned long fixed_rate)
+{
+	struct clk_plt_fixed *pclk;
+
+	pclk = devm_kzalloc(&pdev->dev, sizeof(*pclk), GFP_KERNEL);
+	if (!pclk)
+		return ERR_PTR(-ENOMEM);
+
+	pclk->clk = clk_hw_register_fixed_rate(&pdev->dev, name, parent_name,
+					       0, fixed_rate);
+	if (IS_ERR(pclk->clk))
+		return ERR_CAST(pclk->clk);
+
+	pclk->lookup = clkdev_hw_create(pclk->clk, name, NULL);
+	if (!pclk->lookup) {
+		clk_hw_unregister_fixed_rate(pclk->clk);
+		return ERR_PTR(-ENOMEM);
+	}
+
+	return pclk;
+}
+
+static void plt_clk_unregister_fixed_rate(struct clk_plt_fixed *pclk)
+{
+	clkdev_drop(pclk->lookup);
+	clk_hw_unregister_fixed_rate(pclk->clk);
+}
+
+static void plt_clk_unregister_fixed_rate_loop(struct clk_plt_data *data,
+					       unsigned int i)
+{
+	while (i--)
+		plt_clk_unregister_fixed_rate(data->parents[i]);
+}
+
+static void plt_clk_free_parent_names_loop(const char **parent_names,
+					   unsigned int i)
+{
+	while (i--)
+		kfree_const(parent_names[i]);
+	kfree(parent_names);
+}
+
+static void plt_clk_unregister_loop(struct clk_plt_data *data,
+				    unsigned int i)
+{
+	while (i--)
+		plt_clk_unregister(data->clks[i]);
+}
+
+static const char **plt_clk_register_parents(struct platform_device *pdev,
+					     struct clk_plt_data *data,
+					     const struct pmc_clk *clks)
+{
+	const char **parent_names;
+	unsigned int i;
+	int err;
+	int nparents = 0;
+
+	data->nparents = 0;
+	while (clks[nparents].name)
+		nparents++;
+
+	data->parents = devm_kcalloc(&pdev->dev, nparents,
+				     sizeof(*data->parents), GFP_KERNEL);
+	if (!data->parents)
+		return ERR_PTR(-ENOMEM);
+
+	parent_names = kcalloc(nparents, sizeof(*parent_names),
+			       GFP_KERNEL);
+	if (!parent_names)
+		return ERR_PTR(-ENOMEM);
+
+	for (i = 0; i < nparents; i++) {
+		data->parents[i] =
+			plt_clk_register_fixed_rate(pdev, clks[i].name,
+						    clks[i].parent_name,
+						    clks[i].freq);
+		if (IS_ERR(data->parents[i])) {
+			err = PTR_ERR(data->parents[i]);
+			goto err_unreg;
+		}
+		parent_names[i] = kstrdup_const(clks[i].name, GFP_KERNEL);
+	}
+
+	data->nparents = nparents;
+	return parent_names;
+
+err_unreg:
+	plt_clk_unregister_fixed_rate_loop(data, i);
+	plt_clk_free_parent_names_loop(parent_names, i);
+	return ERR_PTR(err);
+}
+
+static void plt_clk_unregister_parents(struct clk_plt_data *data)
+{
+	plt_clk_unregister_fixed_rate_loop(data, data->nparents);
+}
+
+static int plt_clk_probe(struct platform_device *pdev)
+{
+	const struct pmc_clk_data *pmc_data;
+	const char **parent_names;
+	struct clk_plt_data *data;
+	unsigned int i;
+	int err;
+
+	pmc_data = dev_get_platdata(&pdev->dev);
+	if (!pmc_data || !pmc_data->clks)
+		return -EINVAL;
+
+	data = devm_kzalloc(&pdev->dev, sizeof(*data), GFP_KERNEL);
+	if (!data)
+		return -ENOMEM;
+
+	parent_names = plt_clk_register_parents(pdev, data, pmc_data->clks);
+	if (IS_ERR(parent_names))
+		return PTR_ERR(parent_names);
+
+	for (i = 0; i < PMC_CLK_NUM; i++) {
+		data->clks[i] = plt_clk_register(pdev, i, pmc_data->base,
+						 parent_names, data->nparents);
+		if (IS_ERR(data->clks[i])) {
+			err = PTR_ERR(data->clks[i]);
+			goto err_unreg_clk_plt;
+		}
+	}
+
+	plt_clk_free_parent_names_loop(parent_names, data->nparents);
+
+	platform_set_drvdata(pdev, data);
+	return 0;
+
+err_unreg_clk_plt:
+	plt_clk_unregister_loop(data, i);
+	plt_clk_unregister_parents(data);
+	plt_clk_free_parent_names_loop(parent_names, data->nparents);
+	return err;
+}
+
+static int plt_clk_remove(struct platform_device *pdev)
+{
+	struct clk_plt_data *data;
+
+	data = platform_get_drvdata(pdev);
+
+	plt_clk_unregister_loop(data, PMC_CLK_NUM);
+	plt_clk_unregister_parents(data);
+	return 0;
+}
+
+static struct platform_driver plt_clk_driver = {
+	.driver = {
+		.name = "clk-pmc-atom",
+	},
+	.probe = plt_clk_probe,
+	.remove = plt_clk_remove,
+};
+builtin_platform_driver(plt_clk_driver);

include/linux/platform_data/x86/clk-pmc-atom.h

···
+/*
+ * Intel Atom platform clocks for BayTrail and CherryTrail SoC.
+ *
+ * Copyright (C) 2016, Intel Corporation
+ * Author: Irina Tirdea <[e-mail]>
+ *
+ * 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.
+ */
+
+#ifndef __PLATFORM_DATA_X86_CLK_PMC_ATOM_H
+#define __PLATFORM_DATA_X86_CLK_PMC_ATOM_H
+
+/**
+ * struct pmc_clk - PMC platform clock configuration
+ *
+ * @name:	identified, typically pmc_plt_clk_<x>, x=[0..5]
+ * @freq:	in Hz, 19.2MHz  and 25MHz (Baytrail only) supported
+ * @parent_name: one of 'xtal' or 'osc'
+ */
+struct pmc_clk {
+	const char *name;
+	unsigned long freq;
+	const char *parent_name;
+};
+
+/**
+ * struct pmc_clk_data - common PMC clock configuration
+ *
+ * @base:	PMC clock register base offset
+ * @clks:	pointer to set of registered clocks, typically 0..5
+ */
+struct pmc_clk_data {
+	void __iomem *base;
+	const struct pmc_clk *clks;
+};
+
+#endif /* __PLATFORM_DATA_X86_CLK_PMC_ATOM_H */