/*
 * Copyright (C) 2016 IBM Corp.
 *
 * 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/mfd/syscon.h>
#include <linux/platform_device.h>
#include <linux/slab.h>
#include <linux/string.h>
#include "../core.h"
#include "pinctrl-aspeed.h"

int aspeed_pinctrl_get_groups_count(struct pinctrl_dev *pctldev)
{
	struct aspeed_pinctrl_data *pdata = pinctrl_dev_get_drvdata(pctldev);

	return pdata->ngroups;
}

const char *aspeed_pinctrl_get_group_name(struct pinctrl_dev *pctldev,
		unsigned int group)
{
	struct aspeed_pinctrl_data *pdata = pinctrl_dev_get_drvdata(pctldev);

	return pdata->groups[group].name;
}

int aspeed_pinctrl_get_group_pins(struct pinctrl_dev *pctldev,
				  unsigned int group, const unsigned int **pins,
				  unsigned int *npins)
{
	struct aspeed_pinctrl_data *pdata = pinctrl_dev_get_drvdata(pctldev);

	*pins = &pdata->groups[group].pins[0];
	*npins = pdata->groups[group].npins;

	return 0;
}

void aspeed_pinctrl_pin_dbg_show(struct pinctrl_dev *pctldev,
				 struct seq_file *s, unsigned int offset)
{
	seq_printf(s, " %s", dev_name(pctldev->dev));
}

int aspeed_pinmux_get_fn_count(struct pinctrl_dev *pctldev)
{
	struct aspeed_pinctrl_data *pdata = pinctrl_dev_get_drvdata(pctldev);

	return pdata->nfunctions;
}

const char *aspeed_pinmux_get_fn_name(struct pinctrl_dev *pctldev,
				      unsigned int function)
{
	struct aspeed_pinctrl_data *pdata = pinctrl_dev_get_drvdata(pctldev);

	return pdata->functions[function].name;
}

int aspeed_pinmux_get_fn_groups(struct pinctrl_dev *pctldev,
				unsigned int function,
				const char * const **groups,
				unsigned int * const num_groups)
{
	struct aspeed_pinctrl_data *pdata = pinctrl_dev_get_drvdata(pctldev);

	*groups = pdata->functions[function].groups;
	*num_groups = pdata->functions[function].ngroups;

	return 0;
}

static inline void aspeed_sig_desc_print_val(
		const struct aspeed_sig_desc *desc, bool enable, u32 rv)
{
	pr_debug("SCU%x[0x%08x]=0x%x, got 0x%x from 0x%08x\n", desc->reg,
			desc->mask, enable ? desc->enable : desc->disable,
			(rv & desc->mask) >> __ffs(desc->mask), rv);
}

/**
 * Query the enabled or disabled state of a signal descriptor
 *
 * @desc: The signal descriptor of interest
 * @enabled: True to query the enabled state, false to query disabled state
 * @regmap: The SCU regmap instance
 *
 * @return True if the descriptor's bitfield is configured to the state
 * selected by @enabled, false otherwise
 *
 * Evaluation of descriptor state is non-trivial in that it is not a binary
 * outcome: The bitfields can be greater than one bit in size and thus can take
 * a value that is neither the enabled nor disabled state recorded in the
 * descriptor (typically this means a different function to the one of interest
 * is enabled). Thus we must explicitly test for either condition as required.
 */
static bool aspeed_sig_desc_eval(const struct aspeed_sig_desc *desc,
				 bool enabled, struct regmap *map)
{
	unsigned int raw;
	u32 want;

	if (regmap_read(map, desc->reg, &raw) < 0)
		return false;

	aspeed_sig_desc_print_val(desc, enabled, raw);
	want = enabled ? desc->enable : desc->disable;

	return ((raw & desc->mask) >> __ffs(desc->mask)) == want;
}

/**
 * Query the enabled or disabled state for a mux function's signal on a pin
 *
 * @expr: An expression controlling the signal for a mux function on a pin
 * @enabled: True to query the enabled state, false to query disabled state
 * @regmap: The SCU regmap instance
 *
 * @return True if the expression composed by @enabled evaluates true, false
 * otherwise
 *
 * A mux function is enabled or disabled if the function's signal expression
 * for each pin in the function's pin group evaluates true for the desired
 * state. An signal expression evaluates true if all of its associated signal
 * descriptors evaluate true for the desired state.
 *
 * If an expression's state is described by more than one bit, either through
 * multi-bit bitfields in a single signal descriptor or through multiple signal
 * descriptors of a single bit then it is possible for the expression to be in
 * neither the enabled nor disabled state. Thus we must explicitly test for
 * either condition as required.
 */
static bool aspeed_sig_expr_eval(const struct aspeed_sig_expr *expr,
				 bool enabled, struct regmap *map)
{
	int i;

	for (i = 0; i < expr->ndescs; i++) {
		const struct aspeed_sig_desc *desc = &expr->descs[i];

		if (!aspeed_sig_desc_eval(desc, enabled, map))
			return false;
	}

	return true;
}

/**
 * Configure a pin's signal by applying an expression's descriptor state for
 * all descriptors in the expression.
 *
 * @expr: The expression associated with the function whose signal is to be
 *        configured
 * @enable: true to enable an function's signal through a pin's signal
 *          expression, false to disable the function's signal
 * @map: The SCU's regmap instance for pinmux register access.
 *
 * @return true if the expression is configured as requested, false otherwise
 */
static bool aspeed_sig_expr_set(const struct aspeed_sig_expr *expr,
				bool enable, struct regmap *map)
{
	int i;
	bool ret;

	ret = aspeed_sig_expr_eval(expr, enable, map);
	if (ret)
		return ret;

	for (i = 0; i < expr->ndescs; i++) {
		const struct aspeed_sig_desc *desc = &expr->descs[i];
		u32 pattern = enable ? desc->enable : desc->disable;

		/*
		 * Strap registers are configured in hardware or by early-boot
		 * firmware. Treat them as read-only despite that we can write
		 * them. This may mean that certain functions cannot be
		 * deconfigured and is the reason we re-evaluate after writing
		 * all descriptor bits.
		 */
		if (desc->reg == HW_STRAP1 || desc->reg == HW_STRAP2)
			continue;

		ret = regmap_update_bits(map, desc->reg, desc->mask,
				pattern << __ffs(desc->mask)) == 0;

		if (!ret)
			return ret;
	}

	return aspeed_sig_expr_eval(expr, enable, map);
}

static bool aspeed_sig_expr_enable(const struct aspeed_sig_expr *expr,
				   struct regmap *map)
{
	return aspeed_sig_expr_set(expr, true, map);
}

static bool aspeed_sig_expr_disable(const struct aspeed_sig_expr *expr,
				    struct regmap *map)
{
	return aspeed_sig_expr_set(expr, false, map);
}

/**
 * Disable a signal on a pin by disabling all provided signal expressions.
 *
 * @exprs: The list of signal expressions (from a priority level on a pin)
 * @map: The SCU's regmap instance for pinmux register access.
 *
 * @return true if all expressions in the list are successfully disabled, false
 * otherwise
 */
static bool aspeed_disable_sig(const struct aspeed_sig_expr **exprs,
			       struct regmap *map)
{
	bool disabled = true;

	if (!exprs)
		return true;

	while (*exprs) {
		bool ret;

		ret = aspeed_sig_expr_disable(*exprs, map);
		disabled = disabled && ret;

		exprs++;
	}

	return disabled;
}

/**
 * Search for the signal expression needed to enable the pin's signal for the
 * requested function.
 *
 * @exprs: List of signal expressions (haystack)
 * @name: The name of the requested function (needle)
 *
 * @return A pointer to the signal expression whose function tag matches the
 *         provided name, otherwise NULL.
 *
 */
static const struct aspeed_sig_expr *aspeed_find_expr_by_name(
		const struct aspeed_sig_expr **exprs, const char *name)
{
	while (*exprs) {
		if (strcmp((*exprs)->function, name) == 0)
			return *exprs;
		exprs++;
	}

	return NULL;
}

static char *get_defined_attribute(const struct aspeed_pin_desc *pdesc,
				   const char *(*get)(
					   const struct aspeed_sig_expr *))
{
	char *found = NULL;
	size_t len = 0;
	const struct aspeed_sig_expr ***prios, **funcs, *expr;

	prios = pdesc->prios;

	while ((funcs = *prios)) {
		while ((expr = *funcs)) {
			const char *str = get(expr);
			size_t delta = strlen(str) + 2;
			char *expanded;

			expanded = krealloc(found, len + delta + 1, GFP_KERNEL);
			if (!expanded) {
				kfree(found);
				return expanded;
			}

			found = expanded;
			found[len] = '\0';
			len += delta;

			strcat(found, str);
			strcat(found, ", ");

			funcs++;
		}
		prios++;
	}

	if (len < 2) {
		kfree(found);
		return NULL;
	}

	found[len - 2] = '\0';

	return found;
}

static const char *aspeed_sig_expr_function(const struct aspeed_sig_expr *expr)
{
	return expr->function;
}

static char *get_defined_functions(const struct aspeed_pin_desc *pdesc)
{
	return get_defined_attribute(pdesc, aspeed_sig_expr_function);
}

static const char *aspeed_sig_expr_signal(const struct aspeed_sig_expr *expr)
{
	return expr->signal;
}

static char *get_defined_signals(const struct aspeed_pin_desc *pdesc)
{
	return get_defined_attribute(pdesc, aspeed_sig_expr_signal);
}

int aspeed_pinmux_set_mux(struct pinctrl_dev *pctldev, unsigned int function,
			  unsigned int group)
{
	int i;
	const struct aspeed_pinctrl_data *pdata =
		pinctrl_dev_get_drvdata(pctldev);
	const struct aspeed_pin_group *pgroup = &pdata->groups[group];
	const struct aspeed_pin_function *pfunc =
		&pdata->functions[function];

	for (i = 0; i < pgroup->npins; i++) {
		int pin = pgroup->pins[i];
		const struct aspeed_pin_desc *pdesc = pdata->pins[pin].drv_data;
		const struct aspeed_sig_expr *expr = NULL;
		const struct aspeed_sig_expr **funcs;
		const struct aspeed_sig_expr ***prios;

		if (!pdesc)
			return -EINVAL;

		prios = pdesc->prios;

		if (!prios)
			continue;

		/* Disable functions at a higher priority than that requested */
		while ((funcs = *prios)) {
			expr = aspeed_find_expr_by_name(funcs, pfunc->name);

			if (expr)
				break;

			if (!aspeed_disable_sig(funcs, pdata->map))
				return -EPERM;

			prios++;
		}

		if (!expr) {
			char *functions = get_defined_functions(pdesc);
			char *signals = get_defined_signals(pdesc);

			pr_warn("No function %s found on pin %s (%d). Found signal(s) %s for function(s) %s\n",
				pfunc->name, pdesc->name, pin, signals,
				functions);
			kfree(signals);
			kfree(functions);

			return -ENXIO;
		}

		if (!aspeed_sig_expr_enable(expr, pdata->map))
			return -EPERM;
	}

	return 0;
}

static bool aspeed_expr_is_gpio(const struct aspeed_sig_expr *expr)
{
	/*
	 * The signal type is GPIO if the signal name has "GPIO" as a prefix.
	 * strncmp (rather than strcmp) is used to implement the prefix
	 * requirement.
	 *
	 * expr->signal might look like "GPIOT3" in the GPIO case.
	 */
	return strncmp(expr->signal, "GPIO", 4) == 0;
}

static bool aspeed_gpio_in_exprs(const struct aspeed_sig_expr **exprs)
{
	if (!exprs)
		return false;

	while (*exprs) {
		if (aspeed_expr_is_gpio(*exprs))
			return true;
		exprs++;
	}

	return false;
}

int aspeed_gpio_request_enable(struct pinctrl_dev *pctldev,
			       struct pinctrl_gpio_range *range,
			       unsigned int offset)
{
	const struct aspeed_pinctrl_data *pdata =
		pinctrl_dev_get_drvdata(pctldev);
	const struct aspeed_pin_desc *pdesc = pdata->pins[offset].drv_data;
	const struct aspeed_sig_expr ***prios, **funcs, *expr;

	if (!pdesc)
		return -EINVAL;

	prios = pdesc->prios;

	if (!prios)
		return -ENXIO;

	/* Disable any functions of higher priority than GPIO */
	while ((funcs = *prios)) {
		if (aspeed_gpio_in_exprs(funcs))
			break;

		if (!aspeed_disable_sig(funcs, pdata->map))
			return -EPERM;

		prios++;
	}

	if (!funcs) {
		char *signals = get_defined_signals(pdesc);

		pr_warn("No GPIO signal type found on pin %s (%d). Found: %s\n",
			pdesc->name, offset, signals);
		kfree(signals);

		return -ENXIO;
	}

	expr = *funcs;

	/*
	 * Disabling all higher-priority expressions is enough to enable the
	 * lowest-priority signal type. As such it has no associated
	 * expression.
	 */
	if (!expr)
		return 0;

	/*
	 * If GPIO is not the lowest priority signal type, assume there is only
	 * one expression defined to enable the GPIO function
	 */
	if (!aspeed_sig_expr_enable(expr, pdata->map))
		return -EPERM;

	return 0;
}

int aspeed_pinctrl_probe(struct platform_device *pdev,
			 struct pinctrl_desc *pdesc,
			 struct aspeed_pinctrl_data *pdata)
{
	struct device *parent;
	struct pinctrl_dev *pctl;

	parent = pdev->dev.parent;
	if (!parent) {
		dev_err(&pdev->dev, "No parent for syscon pincontroller\n");
		return -ENODEV;
	}

	pdata->map = syscon_node_to_regmap(parent->of_node);
	if (IS_ERR(pdata->map)) {
		dev_err(&pdev->dev, "No regmap for syscon pincontroller parent\n");
		return PTR_ERR(pdata->map);
	}

	pctl = pinctrl_register(pdesc, &pdev->dev, pdata);

	if (IS_ERR(pctl)) {
		dev_err(&pdev->dev, "Failed to register pinctrl\n");
		return PTR_ERR(pctl);
	}

	platform_set_drvdata(pdev, pdata);

	return 0;
}