Commit | Line | Data |
---|---|---|
b2441318 | 1 | /* SPDX-License-Identifier: GPL-2.0 */ |
41c4221c | 2 | /* |
3 | * Mix this utility code with some glue code to get one of several types of | |
4 | * simple SPI master driver. Two do polled word-at-a-time I/O: | |
5 | * | |
6 | * - GPIO/parport bitbangers. Provide chipselect() and txrx_word[](), | |
7 | * expanding the per-word routines from the inline templates below. | |
8 | * | |
9 | * - Drivers for controllers resembling bare shift registers. Provide | |
10 | * chipselect() and txrx_word[](), with custom setup()/cleanup() methods | |
11 | * that use your controller's clock and chipselect registers. | |
12 | * | |
13 | * Some hardware works well with requests at spi_transfer scope: | |
14 | * | |
15 | * - Drivers leveraging smarter hardware, with fifos or DMA; or for half | |
16 | * duplex (MicroWire) controllers. Provide chipselect() and txrx_bufs(), | |
17 | * and custom setup()/cleanup() methods. | |
18 | */ | |
19 | ||
20 | /* | |
21 | * The code that knows what GPIO pins do what should have declared four | |
22 | * functions, ideally as inlines, before including this header: | |
23 | * | |
24 | * void setsck(struct spi_device *, int is_on); | |
25 | * void setmosi(struct spi_device *, int is_on); | |
26 | * int getmiso(struct spi_device *); | |
27 | * void spidelay(unsigned); | |
28 | * | |
29 | * setsck()'s is_on parameter is a zero/nonzero boolean. | |
30 | * | |
31 | * setmosi()'s is_on parameter is a zero/nonzero boolean. | |
32 | * | |
33 | * getmiso() is required to return 0 or 1 only. Any other value is invalid | |
34 | * and will result in improper operation. | |
35 | * | |
36 | * A non-inlined routine would call bitbang_txrx_*() routines. The | |
37 | * main loop could easily compile down to a handful of instructions, | |
38 | * especially if the delay is a NOP (to run at peak speed). | |
39 | * | |
40 | * Since this is software, the timings may not be exactly what your board's | |
41 | * chips need ... there may be several reasons you'd need to tweak timings | |
f21524f5 | 42 | * in these routines, not just to make it faster or slower to match a |
41c4221c | 43 | * particular CPU clock rate. |
1847e304 AF |
44 | * |
45 | * ToDo: Maybe the bitrev macros can be used to improve the code? | |
41c4221c | 46 | */ |
47 | ||
48 | static inline u32 | |
49 | bitbang_txrx_be_cpha0(struct spi_device *spi, | |
04bb2a03 | 50 | unsigned nsecs, unsigned cpol, unsigned flags, |
41c4221c | 51 | u32 word, u8 bits) |
52 | { | |
53 | /* if (cpol == 0) this is SPI_MODE_0; else this is SPI_MODE_2 */ | |
54 | ||
26a67ec4 | 55 | u32 oldbit = (!(word & (1<<(bits-1)))) << 31; |
41c4221c | 56 | /* clock starts at inactive polarity */ |
57 | for (word <<= (32 - bits); likely(bits); bits--) { | |
58 | ||
59 | /* setup MSB (to slave) on trailing edge */ | |
232a5adc MG |
60 | if ((flags & SPI_MASTER_NO_TX) == 0) { |
61 | if ((word & (1 << 31)) != oldbit) { | |
62 | setmosi(spi, word & (1 << 31)); | |
63 | oldbit = word & (1 << 31); | |
64 | } | |
65 | } | |
41c4221c | 66 | spidelay(nsecs); /* T(setup) */ |
67 | ||
68 | setsck(spi, !cpol); | |
69 | spidelay(nsecs); | |
70 | ||
71 | /* sample MSB (from slave) on leading edge */ | |
72 | word <<= 1; | |
04bb2a03 MS |
73 | if ((flags & SPI_MASTER_NO_RX) == 0) |
74 | word |= getmiso(spi); | |
41c4221c | 75 | setsck(spi, cpol); |
76 | } | |
77 | return word; | |
78 | } | |
79 | ||
80 | static inline u32 | |
81 | bitbang_txrx_be_cpha1(struct spi_device *spi, | |
04bb2a03 | 82 | unsigned nsecs, unsigned cpol, unsigned flags, |
41c4221c | 83 | u32 word, u8 bits) |
84 | { | |
85 | /* if (cpol == 0) this is SPI_MODE_1; else this is SPI_MODE_3 */ | |
86 | ||
26a67ec4 | 87 | u32 oldbit = (!(word & (1<<(bits-1)))) << 31; |
41c4221c | 88 | /* clock starts at inactive polarity */ |
89 | for (word <<= (32 - bits); likely(bits); bits--) { | |
90 | ||
91 | /* setup MSB (to slave) on leading edge */ | |
92 | setsck(spi, !cpol); | |
232a5adc MG |
93 | if ((flags & SPI_MASTER_NO_TX) == 0) { |
94 | if ((word & (1 << 31)) != oldbit) { | |
95 | setmosi(spi, word & (1 << 31)); | |
96 | oldbit = word & (1 << 31); | |
97 | } | |
98 | } | |
41c4221c | 99 | spidelay(nsecs); /* T(setup) */ |
100 | ||
101 | setsck(spi, cpol); | |
102 | spidelay(nsecs); | |
103 | ||
104 | /* sample MSB (from slave) on trailing edge */ | |
105 | word <<= 1; | |
04bb2a03 MS |
106 | if ((flags & SPI_MASTER_NO_RX) == 0) |
107 | word |= getmiso(spi); | |
41c4221c | 108 | } |
109 | return word; | |
110 | } | |
1847e304 AF |
111 | |
112 | static inline u32 | |
113 | bitbang_txrx_le_cpha0(struct spi_device *spi, | |
114 | unsigned int nsecs, unsigned int cpol, unsigned int flags, | |
115 | u32 word, u8 bits) | |
116 | { | |
117 | /* if (cpol == 0) this is SPI_MODE_0; else this is SPI_MODE_2 */ | |
118 | ||
46f7ac3d | 119 | u8 rxbit = bits - 1; |
1847e304 AF |
120 | u32 oldbit = !(word & 1); |
121 | /* clock starts at inactive polarity */ | |
122 | for (; likely(bits); bits--) { | |
123 | ||
124 | /* setup LSB (to slave) on trailing edge */ | |
125 | if ((flags & SPI_MASTER_NO_TX) == 0) { | |
126 | if ((word & 1) != oldbit) { | |
127 | setmosi(spi, word & 1); | |
128 | oldbit = word & 1; | |
129 | } | |
130 | } | |
131 | spidelay(nsecs); /* T(setup) */ | |
132 | ||
133 | setsck(spi, !cpol); | |
134 | spidelay(nsecs); | |
135 | ||
136 | /* sample LSB (from slave) on leading edge */ | |
137 | word >>= 1; | |
138 | if ((flags & SPI_MASTER_NO_RX) == 0) | |
46f7ac3d | 139 | word |= getmiso(spi) << rxbit; |
1847e304 AF |
140 | setsck(spi, cpol); |
141 | } | |
142 | return word; | |
143 | } | |
144 | ||
145 | static inline u32 | |
146 | bitbang_txrx_le_cpha1(struct spi_device *spi, | |
147 | unsigned int nsecs, unsigned int cpol, unsigned int flags, | |
148 | u32 word, u8 bits) | |
149 | { | |
150 | /* if (cpol == 0) this is SPI_MODE_1; else this is SPI_MODE_3 */ | |
151 | ||
46f7ac3d | 152 | u8 rxbit = bits - 1; |
1847e304 AF |
153 | u32 oldbit = !(word & 1); |
154 | /* clock starts at inactive polarity */ | |
155 | for (; likely(bits); bits--) { | |
156 | ||
157 | /* setup LSB (to slave) on leading edge */ | |
158 | setsck(spi, !cpol); | |
159 | if ((flags & SPI_MASTER_NO_TX) == 0) { | |
160 | if ((word & 1) != oldbit) { | |
161 | setmosi(spi, word & 1); | |
162 | oldbit = word & 1; | |
163 | } | |
164 | } | |
165 | spidelay(nsecs); /* T(setup) */ | |
166 | ||
167 | setsck(spi, cpol); | |
168 | spidelay(nsecs); | |
169 | ||
170 | /* sample LSB (from slave) on trailing edge */ | |
171 | word >>= 1; | |
172 | if ((flags & SPI_MASTER_NO_RX) == 0) | |
46f7ac3d | 173 | word |= getmiso(spi) << rxbit; |
1847e304 AF |
174 | } |
175 | return word; | |
176 | } |