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David Brownell9904f222006-01-08 13:34:26 -08001#ifndef __SPI_BITBANG_H
2#define __SPI_BITBANG_H
3
4/*
5 * Mix this utility code with some glue code to get one of several types of
6 * simple SPI master driver. Two do polled word-at-a-time I/O:
7 *
8 * - GPIO/parport bitbangers. Provide chipselect() and txrx_word[](),
9 * expanding the per-word routines from the inline templates below.
10 *
11 * - Drivers for controllers resembling bare shift registers. Provide
12 * chipselect() and txrx_word[](), with custom setup()/cleanup() methods
13 * that use your controller's clock and chipselect registers.
14 *
15 * Some hardware works well with requests at spi_transfer scope:
16 *
17 * - Drivers leveraging smarter hardware, with fifos or DMA; or for half
18 * duplex (MicroWire) controllers. Provide chipslect() and txrx_bufs(),
19 * and custom setup()/cleanup() methods.
20 */
Fernando Luis Vazquez Caoeffdb942008-10-29 14:01:21 -070021
22#include <linux/workqueue.h>
23
David Brownell9904f222006-01-08 13:34:26 -080024struct spi_bitbang {
25 struct workqueue_struct *workqueue;
26 struct work_struct work;
27
28 spinlock_t lock;
29 struct list_head queue;
30 u8 busy;
David Brownell9904f222006-01-08 13:34:26 -080031 u8 use_dma;
David Brownelldccd5732007-07-17 04:04:02 -070032 u8 flags; /* extra spi->mode support */
David Brownell9904f222006-01-08 13:34:26 -080033
34 struct spi_master *master;
35
Imre Deak4cff33f2006-02-17 10:02:18 -080036 /* setup_transfer() changes clock and/or wordsize to match settings
37 * for this transfer; zeroes restore defaults from spi_device.
38 */
39 int (*setup_transfer)(struct spi_device *spi,
40 struct spi_transfer *t);
41
David Brownell9904f222006-01-08 13:34:26 -080042 void (*chipselect)(struct spi_device *spi, int is_on);
Vitaly Wool8275c642006-01-08 13:34:28 -080043#define BITBANG_CS_ACTIVE 1 /* normally nCS, active low */
44#define BITBANG_CS_INACTIVE 0
David Brownell9904f222006-01-08 13:34:26 -080045
Vitaly Wool8275c642006-01-08 13:34:28 -080046 /* txrx_bufs() may handle dma mapping for transfers that don't
47 * already have one (transfer.{tx,rx}_dma is zero), or use PIO
48 */
David Brownell9904f222006-01-08 13:34:26 -080049 int (*txrx_bufs)(struct spi_device *spi, struct spi_transfer *t);
Vitaly Wool8275c642006-01-08 13:34:28 -080050
51 /* txrx_word[SPI_MODE_*]() just looks like a shift register */
David Brownell9904f222006-01-08 13:34:26 -080052 u32 (*txrx_word[4])(struct spi_device *spi,
53 unsigned nsecs,
54 u32 word, u8 bits);
55};
56
57/* you can call these default bitbang->master methods from your custom
58 * methods, if you like.
59 */
60extern int spi_bitbang_setup(struct spi_device *spi);
Hans-Peter Nilsson0ffa0282007-02-12 00:52:45 -080061extern void spi_bitbang_cleanup(struct spi_device *spi);
David Brownell9904f222006-01-08 13:34:26 -080062extern int spi_bitbang_transfer(struct spi_device *spi, struct spi_message *m);
Kumar Galaff9f4772006-04-02 16:06:35 -050063extern int spi_bitbang_setup_transfer(struct spi_device *spi,
64 struct spi_transfer *t);
David Brownell9904f222006-01-08 13:34:26 -080065
66/* start or stop queue processing */
67extern int spi_bitbang_start(struct spi_bitbang *spi);
68extern int spi_bitbang_stop(struct spi_bitbang *spi);
69
70#endif /* __SPI_BITBANG_H */
71
72/*-------------------------------------------------------------------------*/
73
74#ifdef EXPAND_BITBANG_TXRX
75
76/*
77 * The code that knows what GPIO pins do what should have declared four
78 * functions, ideally as inlines, before #defining EXPAND_BITBANG_TXRX
79 * and including this header:
80 *
81 * void setsck(struct spi_device *, int is_on);
82 * void setmosi(struct spi_device *, int is_on);
83 * int getmiso(struct spi_device *);
84 * void spidelay(unsigned);
85 *
Michael Buesch01b24fe2009-02-20 15:38:49 -080086 * setsck()'s is_on parameter is a zero/nonzero boolean.
87 *
88 * setmosi()'s is_on parameter is a zero/nonzero boolean.
89 *
90 * getmiso() is required to return 0 or 1 only. Any other value is invalid
91 * and will result in improper operation.
92 *
David Brownell9904f222006-01-08 13:34:26 -080093 * A non-inlined routine would call bitbang_txrx_*() routines. The
94 * main loop could easily compile down to a handful of instructions,
95 * especially if the delay is a NOP (to run at peak speed).
96 *
97 * Since this is software, the timings may not be exactly what your board's
98 * chips need ... there may be several reasons you'd need to tweak timings
99 * in these routines, not just make to make it faster or slower to match a
100 * particular CPU clock rate.
101 */
102
103static inline u32
104bitbang_txrx_be_cpha0(struct spi_device *spi,
105 unsigned nsecs, unsigned cpol,
106 u32 word, u8 bits)
107{
108 /* if (cpol == 0) this is SPI_MODE_0; else this is SPI_MODE_2 */
109
110 /* clock starts at inactive polarity */
111 for (word <<= (32 - bits); likely(bits); bits--) {
112
113 /* setup MSB (to slave) on trailing edge */
114 setmosi(spi, word & (1 << 31));
115 spidelay(nsecs); /* T(setup) */
116
117 setsck(spi, !cpol);
118 spidelay(nsecs);
119
120 /* sample MSB (from slave) on leading edge */
121 word <<= 1;
122 word |= getmiso(spi);
123 setsck(spi, cpol);
124 }
125 return word;
126}
127
128static inline u32
129bitbang_txrx_be_cpha1(struct spi_device *spi,
130 unsigned nsecs, unsigned cpol,
131 u32 word, u8 bits)
132{
133 /* if (cpol == 0) this is SPI_MODE_1; else this is SPI_MODE_3 */
134
135 /* clock starts at inactive polarity */
136 for (word <<= (32 - bits); likely(bits); bits--) {
137
138 /* setup MSB (to slave) on leading edge */
139 setsck(spi, !cpol);
140 setmosi(spi, word & (1 << 31));
141 spidelay(nsecs); /* T(setup) */
142
143 setsck(spi, cpol);
144 spidelay(nsecs);
145
146 /* sample MSB (from slave) on trailing edge */
147 word <<= 1;
148 word |= getmiso(spi);
149 }
150 return word;
151}
152
153#endif /* EXPAND_BITBANG_TXRX */