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	.devmodel = true,
319};
320module_parport_driver(butterfly_driver);
321
322MODULE_DESCRIPTION("Parport Adapter driver for AVR Butterfly");
323MODULE_LICENSE("GPL");
324