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Linux/drivers/mtd/maps/gpio-addr-flash.c

  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  */
 43 struct 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  */
 63 static 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  */
 82 static 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  */
105 static 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  */
131 static 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  */
151 static 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 
173 static 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  */
204 static 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 
277 static 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 
290 static 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 
298 module_platform_driver(gpio_flash_driver);
299 
300 MODULE_AUTHOR("Mike Frysinger <vapier@gentoo.org>");
301 MODULE_DESCRIPTION("MTD map driver for flashes addressed physically and with gpios");
302 MODULE_LICENSE("GPL");
303 

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