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1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * parport-to-butterfly adapter
4 *
5 * Copyright (C) 2005 David Brownell
6 */
7#include <linux/kernel.h>
8#include <linux/init.h>
9#include <linux/delay.h>
10#include <linux/module.h>
11#include <linux/device.h>
12#include <linux/parport.h>
13
14#include <linux/sched.h>
15#include <linux/spi/spi.h>
16#include <linux/spi/spi_bitbang.h>
17#include <linux/spi/flash.h>
18
19#include <linux/mtd/partitions.h>
20
21/*
22 * This uses SPI to talk with an "AVR Butterfly", which is a $US20 card
23 * with a battery powered AVR microcontroller and lots of goodies. You
24 * can use GCC to develop firmware for this.
25 *
26 * See Documentation/spi/butterfly.rst for information about how to build
27 * and use this custom parallel port cable.
28 */
29
30/* DATA output bits (pins 2..9 == D0..D7) */
31#define butterfly_nreset (1 << 1) /* pin 3 */
32
33#define spi_sck_bit (1 << 0) /* pin 2 */
34#define spi_mosi_bit (1 << 7) /* pin 9 */
35
36#define vcc_bits ((1 << 6) | (1 << 5)) /* pins 7, 8 */
37
38/* STATUS input bits */
39#define spi_miso_bit PARPORT_STATUS_BUSY /* pin 11 */
40
41/* CONTROL output bits */
42#define spi_cs_bit PARPORT_CONTROL_SELECT /* pin 17 */
43
44static inline struct butterfly *spidev_to_pp(struct spi_device *spi)
45{
46 return spi->controller_data;
47}
48
49struct butterfly {
50 /* REVISIT ... for now, this must be first */
51 struct spi_bitbang bitbang;
52
53 struct parport *port;
54 struct pardevice *pd;
55
56 u8 lastbyte;
57
58 struct spi_device *dataflash;
59 struct spi_device *butterfly;
60 struct spi_board_info info[2];
61
62};
63
64/*----------------------------------------------------------------------*/
65
66static inline void
67setsck(struct spi_device *spi, int is_on)
68{
69 struct butterfly *pp = spidev_to_pp(spi);
70 u8 bit, byte = pp->lastbyte;
71
72 bit = spi_sck_bit;
73
74 if (is_on)
75 byte |= bit;
76 else
77 byte &= ~bit;
78 parport_write_data(pp->port, byte);
79 pp->lastbyte = byte;
80}
81
82static inline void
83setmosi(struct spi_device *spi, int is_on)
84{
85 struct butterfly *pp = spidev_to_pp(spi);
86 u8 bit, byte = pp->lastbyte;
87
88 bit = spi_mosi_bit;
89
90 if (is_on)
91 byte |= bit;
92 else
93 byte &= ~bit;
94 parport_write_data(pp->port, byte);
95 pp->lastbyte = byte;
96}
97
98static inline int getmiso(struct spi_device *spi)
99{
100 struct butterfly *pp = spidev_to_pp(spi);
101 int value;
102 u8 bit;
103
104 bit = spi_miso_bit;
105
106 /* only STATUS_BUSY is NOT negated */
107 value = !(parport_read_status(pp->port) & bit);
108 return (bit == PARPORT_STATUS_BUSY) ? value : !value;
109}
110
111static void butterfly_chipselect(struct spi_device *spi, int value)
112{
113 struct butterfly *pp = spidev_to_pp(spi);
114
115 /* set default clock polarity */
116 if (value != BITBANG_CS_INACTIVE)
117 setsck(spi, spi->mode & SPI_CPOL);
118
119 /* here, value == "activate or not";
120 * most PARPORT_CONTROL_* bits are negated, so we must
121 * morph it to value == "bit value to write in control register"
122 */
123 if (spi_cs_bit == PARPORT_CONTROL_INIT)
124 value = !value;
125
126 parport_frob_control(pp->port, spi_cs_bit, value ? spi_cs_bit : 0);
127}
128
129/* we only needed to implement one mode here, and choose SPI_MODE_0 */
130
131#define spidelay(X) do { } while (0)
132/* #define spidelay ndelay */
133
134#include "spi-bitbang-txrx.h"
135
136static u32
137butterfly_txrx_word_mode0(struct spi_device *spi, unsigned nsecs, u32 word,
138 u8 bits, unsigned flags)
139{
140 return bitbang_txrx_be_cpha0(spi, nsecs, 0, flags, word, bits);
141}
142
143/*----------------------------------------------------------------------*/
144
145/* override default partitioning with cmdlinepart */
146static struct mtd_partition partitions[] = { {
147 /* JFFS2 wants partitions of 4*N blocks for this device,
148 * so sectors 0 and 1 can't be partitions by themselves.
149 */
150
151 /* sector 0 = 8 pages * 264 bytes/page (1 block)
152 * sector 1 = 248 pages * 264 bytes/page
153 */
154 .name = "bookkeeping", /* 66 KB */
155 .offset = 0,
156 .size = (8 + 248) * 264,
157 /* .mask_flags = MTD_WRITEABLE, */
158}, {
159 /* sector 2 = 256 pages * 264 bytes/page
160 * sectors 3-5 = 512 pages * 264 bytes/page
161 */
162 .name = "filesystem", /* 462 KB */
163 .offset = MTDPART_OFS_APPEND,
164 .size = MTDPART_SIZ_FULL,
165} };
166
167static struct flash_platform_data flash = {
168 .name = "butterflash",
169 .parts = partitions,
170 .nr_parts = ARRAY_SIZE(partitions),
171};
172
173/* REVISIT remove this ugly global and its "only one" limitation */
174static struct butterfly *butterfly;
175
176static void butterfly_attach(struct parport *p)
177{
178 struct pardevice *pd;
179 int status;
180 struct butterfly *pp;
181 struct spi_controller *host;
182 struct device *dev = p->physport->dev;
183 struct pardev_cb butterfly_cb;
184
185 if (butterfly || !dev)
186 return;
187
188 /* REVISIT: this just _assumes_ a butterfly is there ... no probe,
189 * and no way to be selective about what it binds to.
190 */
191
192 host = spi_alloc_host(dev, sizeof(*pp));
193 if (!host) {
194 status = -ENOMEM;
195 goto done;
196 }
197 pp = spi_controller_get_devdata(host);
198
199 /*
200 * SPI and bitbang hookup
201 *
202 * use default setup(), cleanup(), and transfer() methods; and
203 * only bother implementing mode 0. Start it later.
204 */
205 host->bus_num = 42;
206 host->num_chipselect = 2;
207
208 pp->bitbang.ctlr = host;
209 pp->bitbang.chipselect = butterfly_chipselect;
210 pp->bitbang.txrx_word[SPI_MODE_0] = butterfly_txrx_word_mode0;
211
212 /*
213 * parport hookup
214 */
215 pp->port = p;
216 memset(&butterfly_cb, 0, sizeof(butterfly_cb));
217 butterfly_cb.private = pp;
218 pd = parport_register_dev_model(p, "spi_butterfly", &butterfly_cb, 0);
219 if (!pd) {
220 status = -ENOMEM;
221 goto clean0;
222 }
223 pp->pd = pd;
224
225 status = parport_claim(pd);
226 if (status < 0)
227 goto clean1;
228
229 /*
230 * Butterfly reset, powerup, run firmware
231 */
232 pr_debug("%s: powerup/reset Butterfly\n", p->name);
233
234 /* nCS for dataflash (this bit is inverted on output) */
235 parport_frob_control(pp->port, spi_cs_bit, 0);
236
237 /* stabilize power with chip in reset (nRESET), and
238 * spi_sck_bit clear (CPOL=0)
239 */
240 pp->lastbyte |= vcc_bits;
241 parport_write_data(pp->port, pp->lastbyte);
242 msleep(5);
243
244 /* take it out of reset; assume long reset delay */
245 pp->lastbyte |= butterfly_nreset;
246 parport_write_data(pp->port, pp->lastbyte);
247 msleep(100);
248
249 /*
250 * Start SPI ... for now, hide that we're two physical busses.
251 */
252 status = spi_bitbang_start(&pp->bitbang);
253 if (status < 0)
254 goto clean2;
255
256 /* Bus 1 lets us talk to at45db041b (firmware disables AVR SPI), AVR
257 * (firmware resets at45, acts as spi slave) or neither (we ignore
258 * both, AVR uses AT45). Here we expect firmware for the first option.
259 */
260
261 pp->info[0].max_speed_hz = 15 * 1000 * 1000;
262 strcpy(pp->info[0].modalias, "mtd_dataflash");
263 pp->info[0].platform_data = &flash;
264 pp->info[0].chip_select = 1;
265 pp->info[0].controller_data = pp;
266 pp->dataflash = spi_new_device(pp->bitbang.ctlr, &pp->info[0]);
267 if (pp->dataflash)
268 pr_debug("%s: dataflash at %s\n", p->name,
269 dev_name(&pp->dataflash->dev));
270
271 pr_info("%s: AVR Butterfly\n", p->name);
272 butterfly = pp;
273 return;
274
275clean2:
276 /* turn off VCC */
277 parport_write_data(pp->port, 0);
278
279 parport_release(pp->pd);
280clean1:
281 parport_unregister_device(pd);
282clean0:
283 spi_controller_put(host);
284done:
285 pr_debug("%s: butterfly probe, fail %d\n", p->name, status);
286}
287
288static void butterfly_detach(struct parport *p)
289{
290 struct butterfly *pp;
291
292 /* FIXME this global is ugly ... but, how to quickly get from
293 * the parport to the "struct butterfly" associated with it?
294 * "old school" driver-internal device lists?
295 */
296 if (!butterfly || butterfly->port != p)
297 return;
298 pp = butterfly;
299 butterfly = NULL;
300
301 /* stop() unregisters child devices too */
302 spi_bitbang_stop(&pp->bitbang);
303
304 /* turn off VCC */
305 parport_write_data(pp->port, 0);
306 msleep(10);
307
308 parport_release(pp->pd);
309 parport_unregister_device(pp->pd);
310
311 spi_controller_put(pp->bitbang.ctlr);
312}
313
314static struct parport_driver butterfly_driver = {
315 .name = "spi_butterfly",
316 .match_port = butterfly_attach,
317 .detach = butterfly_detach,
318};
319module_parport_driver(butterfly_driver);
320
321MODULE_DESCRIPTION("Parport Adapter driver for AVR Butterfly");
322MODULE_LICENSE("GPL");