cachepc-linux

Fork of AMDESE/linux with modifications for CachePC side-channel attack
git clone https://git.sinitax.com/sinitax/cachepc-linux
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gpio-gw-pld.c (3160B)

      1// SPDX-License-Identifier: GPL-2.0+
      2//
      3// Gateworks I2C PLD GPIO expander
      4//
      5// Copyright (C) 2019 Linus Walleij <linus.walleij@linaro.org>
      6//
      7// Based on code and know-how from the OpenWrt driver:
      8// Copyright (C) 2009 Gateworks Corporation
      9// Authors: Chris Lang, Imre Kaloz
     10
     11#include <linux/bits.h>
     12#include <linux/kernel.h>
     13#include <linux/slab.h>
     14#include <linux/gpio/driver.h>
     15#include <linux/i2c.h>
     16#include <linux/module.h>
     17
     18/**
     19 * struct gw_pld - State container for Gateworks PLD
     20 * @chip: GPIO chip instance
     21 * @client: I2C client
     22 * @out: shadow register for the output bute
     23 */
     24struct gw_pld {
     25	struct gpio_chip chip;
     26	struct i2c_client *client;
     27	u8 out;
     28};
     29
     30/*
     31 * The Gateworks I2C PLD chip only expose one read and one write register.
     32 * Writing a "one" bit (to match the reset state) lets that pin be used as an
     33 * input. It is an open-drain model.
     34 */
     35static int gw_pld_input8(struct gpio_chip *gc, unsigned offset)
     36{
     37	struct gw_pld *gw = gpiochip_get_data(gc);
     38
     39	gw->out |= BIT(offset);
     40	return i2c_smbus_write_byte(gw->client, gw->out);
     41}
     42
     43static int gw_pld_get8(struct gpio_chip *gc, unsigned offset)
     44{
     45	struct gw_pld *gw = gpiochip_get_data(gc);
     46	s32 val;
     47
     48	val = i2c_smbus_read_byte(gw->client);
     49
     50	return (val < 0) ? 0 : !!(val & BIT(offset));
     51}
     52
     53static int gw_pld_output8(struct gpio_chip *gc, unsigned offset, int value)
     54{
     55	struct gw_pld *gw = gpiochip_get_data(gc);
     56
     57	if (value)
     58		gw->out |= BIT(offset);
     59	else
     60		gw->out &= ~BIT(offset);
     61
     62	return i2c_smbus_write_byte(gw->client, gw->out);
     63}
     64
     65static void gw_pld_set8(struct gpio_chip *gc, unsigned offset, int value)
     66{
     67	gw_pld_output8(gc, offset, value);
     68}
     69
     70static int gw_pld_probe(struct i2c_client *client,
     71			const struct i2c_device_id *id)
     72{
     73	struct device *dev = &client->dev;
     74	struct gw_pld *gw;
     75	int ret;
     76
     77	gw = devm_kzalloc(dev, sizeof(*gw), GFP_KERNEL);
     78	if (!gw)
     79		return -ENOMEM;
     80
     81	gw->chip.base = -1;
     82	gw->chip.can_sleep = true;
     83	gw->chip.parent = dev;
     84	gw->chip.owner = THIS_MODULE;
     85	gw->chip.label = dev_name(dev);
     86	gw->chip.ngpio = 8;
     87	gw->chip.direction_input = gw_pld_input8;
     88	gw->chip.get = gw_pld_get8;
     89	gw->chip.direction_output = gw_pld_output8;
     90	gw->chip.set = gw_pld_set8;
     91	gw->client = client;
     92
     93	/*
     94	 * The Gateworks I2C PLD chip does not properly send the acknowledge
     95	 * bit at all times, but we can still use the standard i2c_smbus
     96	 * functions by simply ignoring this bit.
     97	 */
     98	client->flags |= I2C_M_IGNORE_NAK;
     99	gw->out = 0xFF;
    100
    101	i2c_set_clientdata(client, gw);
    102
    103	ret = devm_gpiochip_add_data(dev, &gw->chip, gw);
    104	if (ret)
    105		return ret;
    106
    107	dev_info(dev, "registered Gateworks PLD GPIO device\n");
    108
    109	return 0;
    110}
    111
    112static const struct i2c_device_id gw_pld_id[] = {
    113	{ "gw-pld", },
    114	{ }
    115};
    116MODULE_DEVICE_TABLE(i2c, gw_pld_id);
    117
    118static const struct of_device_id gw_pld_dt_ids[] = {
    119	{ .compatible = "gateworks,pld-gpio", },
    120	{ },
    121};
    122MODULE_DEVICE_TABLE(of, gw_pld_dt_ids);
    123
    124static struct i2c_driver gw_pld_driver = {
    125	.driver = {
    126		.name = "gw_pld",
    127		.of_match_table = gw_pld_dt_ids,
    128	},
    129	.probe = gw_pld_probe,
    130	.id_table = gw_pld_id,
    131};
    132module_i2c_driver(gw_pld_driver);
    133
    134MODULE_LICENSE("GPL");
    135MODULE_AUTHOR("Linus Walleij <linus.walleij@linaro.org>");