1/*
2 * drivers/mtd/maps/gpio-addr-flash.c
3 *
4 * Handle the case where a flash device is mostly addressed using physical
5 * line and supplemented by GPIOs.  This way you can hook up say a 8MiB flash
6 * to a 2MiB memory range and use the GPIOs to select a particular range.
7 *
8 * Copyright © 2000 Nicolas Pitre <nico@cam.org>
9 * Copyright © 2005-2009 Analog Devices Inc.
10 *
11 * Enter bugs at http://blackfin.uclinux.org/
12 *
13 * Licensed under the GPL-2 or later.
14 */
15
16#include <linux/gpio.h>
17#include <linux/io.h>
18#include <linux/kernel.h>
19#include <linux/module.h>
20#include <linux/mtd/mtd.h>
21#include <linux/mtd/map.h>
22#include <linux/mtd/partitions.h>
23#include <linux/mtd/physmap.h>
24#include <linux/platform_device.h>
25#include <linux/slab.h>
26#include <linux/types.h>
27
28#define pr_devinit(fmt, args...) \
29	({ static const char __fmt[] = fmt; printk(__fmt, ## args); })
30
31#define DRIVER_NAME "gpio-addr-flash"
32#define PFX DRIVER_NAME ": "
33
34/**
35 * struct async_state - keep GPIO flash state
36 *	@mtd:         MTD state for this mapping
37 *	@map:         MTD map state for this flash
38 *	@gpio_count:  number of GPIOs used to address
39 *	@gpio_addrs:  array of GPIOs to twiddle
40 *	@gpio_values: cached GPIO values
41 *	@win_size:    dedicated memory size (if no GPIOs)
42 */
43struct async_state {
44	struct mtd_info *mtd;
45	struct map_info map;
46	size_t gpio_count;
47	unsigned *gpio_addrs;
48	int *gpio_values;
49	unsigned long win_size;
50};
51#define gf_map_info_to_state(mi) ((struct async_state *)(mi)->map_priv_1)
52
53/**
54 * gf_set_gpios() - set GPIO address lines to access specified flash offset
55 *	@state: GPIO flash state
56 *	@ofs:   desired offset to access
57 *
58 * Rather than call the GPIO framework every time, cache the last-programmed
59 * value.  This speeds up sequential accesses (which are by far the most common
60 * type).  We rely on the GPIO framework to treat non-zero value as high so
61 * that we don't have to normalize the bits.
62 */
63static void gf_set_gpios(struct async_state *state, unsigned long ofs)
64{
65	size_t i = 0;
66	int value;
67	ofs /= state->win_size;
68	do {
69		value = ofs & (1 << i);
70		if (state->gpio_values[i] != value) {
71			gpio_set_value(state->gpio_addrs[i], value);
72			state->gpio_values[i] = value;
73		}
74	} while (++i < state->gpio_count);
75}
76
77/**
78 * gf_read() - read a word at the specified offset
79 *	@map: MTD map state
80 *	@ofs: desired offset to read
81 */
82static map_word gf_read(struct map_info *map, unsigned long ofs)
83{
84	struct async_state *state = gf_map_info_to_state(map);
85	uint16_t word;
86	map_word test;
87
88	gf_set_gpios(state, ofs);
89
90	word = readw(map->virt + (ofs % state->win_size));
91	test.x[0] = word;
92	return test;
93}
94
95/**
96 * gf_copy_from() - copy a chunk of data from the flash
97 *	@map:  MTD map state
98 *	@to:   memory to copy to
99 *	@from: flash offset to copy from
100 *	@len:  how much to copy
101 *
102 * The "from" region may straddle more than one window, so toggle the GPIOs for
103 * each window region before reading its data.
104 */
105static void gf_copy_from(struct map_info *map, void *to, unsigned long from, ssize_t len)
106{
107	struct async_state *state = gf_map_info_to_state(map);
108
109	int this_len;
110
111	while (len) {
112		if ((from % state->win_size) + len > state->win_size)
113			this_len = state->win_size - (from % state->win_size);
114		else
115			this_len = len;
116
117		gf_set_gpios(state, from);
118		memcpy_fromio(to, map->virt + (from % state->win_size),
119			 this_len);
120		len -= this_len;
121		from += this_len;
122		to += this_len;
123	}
124}
125
126/**
127 * gf_write() - write a word at the specified offset
128 *	@map: MTD map state
129 *	@ofs: desired offset to write
130 */
131static void gf_write(struct map_info *map, map_word d1, unsigned long ofs)
132{
133	struct async_state *state = gf_map_info_to_state(map);
134	uint16_t d;
135
136	gf_set_gpios(state, ofs);
137
138	d = d1.x[0];
139	writew(d, map->virt + (ofs % state->win_size));
140}
141
142/**
143 * gf_copy_to() - copy a chunk of data to the flash
144 *	@map:  MTD map state
145 *	@to:   flash offset to copy to
146 *	@from: memory to copy from
147 *	@len:  how much to copy
148 *
149 * See gf_copy_from() caveat.
150 */
151static void gf_copy_to(struct map_info *map, unsigned long to,
152		       const void *from, ssize_t len)
153{
154	struct async_state *state = gf_map_info_to_state(map);
155
156	int this_len;
157
158	while (len) {
159		if ((to % state->win_size) + len > state->win_size)
160			this_len = state->win_size - (to % state->win_size);
161		else
162			this_len = len;
163
164		gf_set_gpios(state, to);
165		memcpy_toio(map->virt + (to % state->win_size), from, len);
166
167		len -= this_len;
168		to += this_len;
169		from += this_len;
170	}
171}
172
173static const char * const part_probe_types[] = {
174	"cmdlinepart", "RedBoot", NULL };
175
176/**
177 * gpio_flash_probe() - setup a mapping for a GPIO assisted flash
178 *	@pdev: platform device
179 *
180 * The platform resource layout expected looks something like:
181 * struct mtd_partition partitions[] = { ... };
182 * struct physmap_flash_data flash_data = { ... };
183 * unsigned flash_gpios[] = { GPIO_XX, GPIO_XX, ... };
184 * struct resource flash_resource[] = {
185 *	{
186 *		.name  = "cfi_probe",
187 *		.start = 0x20000000,
188 *		.end   = 0x201fffff,
189 *		.flags = IORESOURCE_MEM,
190 *	}, {
191 *		.start = (unsigned long)flash_gpios,
192 *		.end   = ARRAY_SIZE(flash_gpios),
193 *		.flags = IORESOURCE_IRQ,
194 *	}
195 * };
196 * struct platform_device flash_device = {
197 *	.name          = "gpio-addr-flash",
198 *	.dev           = { .platform_data = &flash_data, },
199 *	.num_resources = ARRAY_SIZE(flash_resource),
200 *	.resource      = flash_resource,
201 *	...
202 * };
203 */
204static int gpio_flash_probe(struct platform_device *pdev)
205{
206	size_t i, arr_size;
207	struct physmap_flash_data *pdata;
208	struct resource *memory;
209	struct resource *gpios;
210	struct async_state *state;
211
212	pdata = dev_get_platdata(&pdev->dev);
213	memory = platform_get_resource(pdev, IORESOURCE_MEM, 0);
214	gpios = platform_get_resource(pdev, IORESOURCE_IRQ, 0);
215
216	if (!memory || !gpios || !gpios->end)
217		return -EINVAL;
218
219	arr_size = sizeof(int) * gpios->end;
220	state = kzalloc(sizeof(*state) + arr_size, GFP_KERNEL);
221	if (!state)
222		return -ENOMEM;
223
224	/*
225	 * We cast start/end to known types in the boards file, so cast
226	 * away their pointer types here to the known types (gpios->xxx).
227	 */
228	state->gpio_count     = gpios->end;
229	state->gpio_addrs     = (void *)(unsigned long)gpios->start;
230	state->gpio_values    = (void *)(state + 1);
231	state->win_size       = resource_size(memory);
232	memset(state->gpio_values, 0xff, arr_size);
233
234	state->map.name       = DRIVER_NAME;
235	state->map.read       = gf_read;
236	state->map.copy_from  = gf_copy_from;
237	state->map.write      = gf_write;
238	state->map.copy_to    = gf_copy_to;
239	state->map.bankwidth  = pdata->width;
240	state->map.size       = state->win_size * (1 << state->gpio_count);
241	state->map.virt       = ioremap_nocache(memory->start, state->map.size);
242	state->map.phys       = NO_XIP;
243	state->map.map_priv_1 = (unsigned long)state;
244
245	platform_set_drvdata(pdev, state);
246
247	i = 0;
248	do {
249		if (gpio_request(state->gpio_addrs[i], DRIVER_NAME)) {
250			pr_devinit(KERN_ERR PFX "failed to request gpio %d\n",
251				state->gpio_addrs[i]);
252			while (i--)
253				gpio_free(state->gpio_addrs[i]);
254			kfree(state);
255			return -EBUSY;
256		}
257		gpio_direction_output(state->gpio_addrs[i], 0);
258	} while (++i < state->gpio_count);
259
260	pr_devinit(KERN_NOTICE PFX "probing %d-bit flash bus\n",
261		state->map.bankwidth * 8);
262	state->mtd = do_map_probe(memory->name, &state->map);
263	if (!state->mtd) {
264		for (i = 0; i < state->gpio_count; ++i)
265			gpio_free(state->gpio_addrs[i]);
266		kfree(state);
267		return -ENXIO;
268	}
269
270
271	mtd_device_parse_register(state->mtd, part_probe_types, NULL,
272				  pdata->parts, pdata->nr_parts);
273
274	return 0;
275}
276
277static int gpio_flash_remove(struct platform_device *pdev)
278{
279	struct async_state *state = platform_get_drvdata(pdev);
280	size_t i = 0;
281	do {
282		gpio_free(state->gpio_addrs[i]);
283	} while (++i < state->gpio_count);
284	mtd_device_unregister(state->mtd);
285	map_destroy(state->mtd);
286	kfree(state);
287	return 0;
288}
289
290static struct platform_driver gpio_flash_driver = {
291	.probe		= gpio_flash_probe,
292	.remove		= gpio_flash_remove,
293	.driver		= {
294		.name	= DRIVER_NAME,
295	},
296};
297
298module_platform_driver(gpio_flash_driver);
299
300MODULE_AUTHOR("Mike Frysinger <vapier@gentoo.org>");
301MODULE_DESCRIPTION("MTD map driver for flashes addressed physically and with gpios");
302MODULE_LICENSE("GPL");
303