linux/drivers/gpio/gpio-mm-lantiq.c
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   1/*
   2 *  This program is free software; you can redistribute it and/or modify it
   3 *  under the terms of the GNU General Public License version 2 as published
   4 *  by the Free Software Foundation.
   5 *
   6 *  Copyright (C) 2012 John Crispin <blogic@openwrt.org>
   7 */
   8
   9#include <linux/init.h>
  10#include <linux/module.h>
  11#include <linux/types.h>
  12#include <linux/platform_device.h>
  13#include <linux/mutex.h>
  14#include <linux/gpio.h>
  15#include <linux/of.h>
  16#include <linux/of_gpio.h>
  17#include <linux/io.h>
  18#include <linux/slab.h>
  19
  20#include <lantiq_soc.h>
  21
  22/*
  23 * By attaching hardware latches to the EBU it is possible to create output
  24 * only gpios. This driver configures a special memory address, which when
  25 * written to outputs 16 bit to the latches.
  26 */
  27
  28#define LTQ_EBU_BUSCON  0x1e7ff         /* 16 bit access, slowest timing */
  29#define LTQ_EBU_WP      0x80000000      /* write protect bit */
  30
  31struct ltq_mm {
  32        struct of_mm_gpio_chip mmchip;
  33        u16 shadow;     /* shadow the latches state */
  34};
  35
  36/**
  37 * ltq_mm_apply() - write the shadow value to the ebu address.
  38 * @chip:     Pointer to our private data structure.
  39 *
  40 * Write the shadow value to the EBU to set the gpios. We need to set the
  41 * global EBU lock to make sure that PCI/MTD dont break.
  42 */
  43static void ltq_mm_apply(struct ltq_mm *chip)
  44{
  45        unsigned long flags;
  46
  47        spin_lock_irqsave(&ebu_lock, flags);
  48        ltq_ebu_w32(LTQ_EBU_BUSCON, LTQ_EBU_BUSCON1);
  49        __raw_writew(chip->shadow, chip->mmchip.regs);
  50        ltq_ebu_w32(LTQ_EBU_BUSCON | LTQ_EBU_WP, LTQ_EBU_BUSCON1);
  51        spin_unlock_irqrestore(&ebu_lock, flags);
  52}
  53
  54/**
  55 * ltq_mm_set() - gpio_chip->set - set gpios.
  56 * @gc:     Pointer to gpio_chip device structure.
  57 * @gpio:   GPIO signal number.
  58 * @val:    Value to be written to specified signal.
  59 *
  60 * Set the shadow value and call ltq_mm_apply.
  61 */
  62static void ltq_mm_set(struct gpio_chip *gc, unsigned offset, int value)
  63{
  64        struct of_mm_gpio_chip *mm_gc = to_of_mm_gpio_chip(gc);
  65        struct ltq_mm *chip =
  66                container_of(mm_gc, struct ltq_mm, mmchip);
  67
  68        if (value)
  69                chip->shadow |= (1 << offset);
  70        else
  71                chip->shadow &= ~(1 << offset);
  72        ltq_mm_apply(chip);
  73}
  74
  75/**
  76 * ltq_mm_dir_out() - gpio_chip->dir_out - set gpio direction.
  77 * @gc:     Pointer to gpio_chip device structure.
  78 * @gpio:   GPIO signal number.
  79 * @val:    Value to be written to specified signal.
  80 *
  81 * Same as ltq_mm_set, always returns 0.
  82 */
  83static int ltq_mm_dir_out(struct gpio_chip *gc, unsigned offset, int value)
  84{
  85        ltq_mm_set(gc, offset, value);
  86
  87        return 0;
  88}
  89
  90/**
  91 * ltq_mm_save_regs() - Set initial values of GPIO pins
  92 * @mm_gc: pointer to memory mapped GPIO chip structure
  93 */
  94static void ltq_mm_save_regs(struct of_mm_gpio_chip *mm_gc)
  95{
  96        struct ltq_mm *chip =
  97                container_of(mm_gc, struct ltq_mm, mmchip);
  98
  99        /* tell the ebu controller which memory address we will be using */
 100        ltq_ebu_w32(CPHYSADDR(chip->mmchip.regs) | 0x1, LTQ_EBU_ADDRSEL1);
 101
 102        ltq_mm_apply(chip);
 103}
 104
 105static int ltq_mm_probe(struct platform_device *pdev)
 106{
 107        struct resource *res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 108        struct ltq_mm *chip;
 109        const __be32 *shadow;
 110        int ret = 0;
 111
 112        if (!res) {
 113                dev_err(&pdev->dev, "failed to get memory resource\n");
 114                return -ENOENT;
 115        }
 116
 117        chip = kzalloc(sizeof(*chip), GFP_KERNEL);
 118        if (!chip)
 119                return -ENOMEM;
 120
 121        chip->mmchip.gc.ngpio = 16;
 122        chip->mmchip.gc.label = "gpio-mm-ltq";
 123        chip->mmchip.gc.direction_output = ltq_mm_dir_out;
 124        chip->mmchip.gc.set = ltq_mm_set;
 125        chip->mmchip.save_regs = ltq_mm_save_regs;
 126
 127        /* store the shadow value if one was passed by the devicetree */
 128        shadow = of_get_property(pdev->dev.of_node, "lantiq,shadow", NULL);
 129        if (shadow)
 130                chip->shadow = be32_to_cpu(*shadow);
 131
 132        ret = of_mm_gpiochip_add(pdev->dev.of_node, &chip->mmchip);
 133        if (ret)
 134                kfree(chip);
 135        return ret;
 136}
 137
 138static const struct of_device_id ltq_mm_match[] = {
 139        { .compatible = "lantiq,gpio-mm" },
 140        {},
 141};
 142MODULE_DEVICE_TABLE(of, ltq_mm_match);
 143
 144static struct platform_driver ltq_mm_driver = {
 145        .probe = ltq_mm_probe,
 146        .driver = {
 147                .name = "gpio-mm-ltq",
 148                .owner = THIS_MODULE,
 149                .of_match_table = ltq_mm_match,
 150        },
 151};
 152
 153static int __init ltq_mm_init(void)
 154{
 155        return platform_driver_register(&ltq_mm_driver);
 156}
 157
 158subsys_initcall(ltq_mm_init);
 159
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