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authorEric Miao <eric.miao@marvell.com>2008-12-25 04:19:02 -0500
committerEric Miao <eric.miao@marvell.com>2008-12-29 04:58:18 -0500
commit5bfb4093be6ac7b6c06c8e6461d85241654acc61 (patch)
tree869dfdd3198803eaa849a185433febaedf6cd073 /Documentation/arm/pxa
parent28a623855f737a905b90a1616107ad813bfcd6e9 (diff)
[ARM] pxa: add document on the MFP design and how to use it
Signed-off-by: Eric Miao <eric.miao@marvell.com>
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1 MFP Configuration for PXA2xx/PXA3xx Processors
2
3 Eric Miao <eric.miao@marvell.com>
4
5MFP stands for Multi-Function Pin, which is the pin-mux logic on PXA3xx and
6later PXA series processors. This document describes the existing MFP API,
7and how board/platform driver authors could make use of it.
8
9 Basic Concept
10===============
11
12Unlike the GPIO alternate function settings on PXA25x and PXA27x, a new MFP
13mechanism is introduced from PXA3xx to completely move the pin-mux functions
14out of the GPIO controller. In addition to pin-mux configurations, the MFP
15also controls the low power state, driving strength, pull-up/down and event
16detection of each pin. Below is a diagram of internal connections between
17the MFP logic and the remaining SoC peripherals:
18
19 +--------+
20 | |--(GPIO19)--+
21 | GPIO | |
22 | |--(GPIO...) |
23 +--------+ |
24 | +---------+
25 +--------+ +------>| |
26 | PWM2 |--(PWM_OUT)-------->| MFP |
27 +--------+ +------>| |-------> to external PAD
28 | +---->| |
29 +--------+ | | +-->| |
30 | SSP2 |---(TXD)----+ | | +---------+
31 +--------+ | |
32 | |
33 +--------+ | |
34 | Keypad |--(MKOUT4)----+ |
35 +--------+ |
36 |
37 +--------+ |
38 | UART2 |---(TXD)--------+
39 +--------+
40
41NOTE: the external pad is named as MFP_PIN_GPIO19, it doesn't necessarily
42mean it's dedicated for GPIO19, only as a hint that internally this pin
43can be routed from GPIO19 of the GPIO controller.
44
45To better understand the change from PXA25x/PXA27x GPIO alternate function
46to this new MFP mechanism, here are several key points:
47
48 1. GPIO controller on PXA3xx is now a dedicated controller, same as other
49 internal controllers like PWM, SSP and UART, with 128 internal signals
50 which can be routed to external through one or more MFPs (e.g. GPIO<0>
51 can be routed through either MFP_PIN_GPIO0 as well as MFP_PIN_GPIO0_2,
52 see arch/arm/mach-pxa/mach/include/mfp-pxa300.h)
53
54 2. Alternate function configuration is removed from this GPIO controller,
55 the remaining functions are pure GPIO-specific, i.e.
56
57 - GPIO signal level control
58 - GPIO direction control
59 - GPIO level change detection
60
61 3. Low power state for each pin is now controlled by MFP, this means the
62 PGSRx registers on PXA2xx are now useless on PXA3xx
63
64 4. Wakeup detection is now controlled by MFP, PWER does not control the
65 wakeup from GPIO(s) any more, depending on the sleeping state, ADxER
66 (as defined in pxa3xx-regs.h) controls the wakeup from MFP
67
68NOTE: with such a clear separation of MFP and GPIO, by GPIO<xx> we normally
69mean it is a GPIO signal, and by MFP<xxx> or pin xxx, we mean a physical
70pad (or ball).
71
72 MFP API Usage
73===============
74
75For board code writers, here are some guidelines:
76
771. include ONE of the following header files in your <board>.c:
78
79 - #include <mach/mfp-pxa25x.h>
80 - #include <mach/mfp-pxa27x.h>
81 - #include <mach/mfp-pxa300.h>
82 - #include <mach/mfp-pxa320.h>
83 - #include <mach/mfp-pxa930.h>
84
85 NOTE: only one file in your <board>.c, depending on the processors used,
86 because pin configuration definitions may conflict in these file (i.e.
87 same name, different meaning and settings on different processors). E.g.
88 for zylonite platform, which support both PXA300/PXA310 and PXA320, two
89 separate files are introduced: zylonite_pxa300.c and zylonite_pxa320.c
90 (in addition to handle MFP configuration differences, they also handle
91 the other differences between the two combinations).
92
93 NOTE: PXA300 and PXA310 are almost identical in pin configurations (with
94 PXA310 supporting some additional ones), thus the difference is actually
95 covered in a single mfp-pxa300.h.
96
972. prepare an array for the initial pin configurations, e.g.:
98
99 static unsigned long mainstone_pin_config[] __initdata = {
100 /* Chip Select */
101 GPIO15_nCS_1,
102
103 /* LCD - 16bpp Active TFT */
104 GPIOxx_TFT_LCD_16BPP,
105 GPIO16_PWM0_OUT, /* Backlight */
106
107 /* MMC */
108 GPIO32_MMC_CLK,
109 GPIO112_MMC_CMD,
110 GPIO92_MMC_DAT_0,
111 GPIO109_MMC_DAT_1,
112 GPIO110_MMC_DAT_2,
113 GPIO111_MMC_DAT_3,
114
115 ...
116
117 /* GPIO */
118 GPIO1_GPIO | WAKEUP_ON_EDGE_BOTH,
119 };
120
121 a) once the pin configurations are passed to pxa{2xx,3xx}_mfp_config(),
122 and written to the actual registers, they are useless and may discard,
123 adding '__initdata' will help save some additional bytes here.
124
125 b) when there is only one possible pin configurations for a component,
126 some simplified definitions can be used, e.g. GPIOxx_TFT_LCD_16BPP on
127 PXA25x and PXA27x processors
128
129 c) if by board design, a pin can be configured to wake up the system
130 from low power state, it can be 'OR'ed with any of:
131
132 WAKEUP_ON_EDGE_BOTH
133 WAKEUP_ON_EDGE_RISE
134 WAKEUP_ON_EDGE_FALL
135 WAKEUP_ON_LEVEL_HIGH - specifically for enabling of keypad GPIOs,
136
137 to indicate that this pin has the capability of wake-up the system,
138 and on which edge(s). This, however, doesn't necessarily mean the
139 pin _will_ wakeup the system, it will only when set_irq_wake() is
140 invoked with the corresponding GPIO IRQ (GPIO_IRQ(xx) or gpio_to_irq())
141 and eventually calls gpio_set_wake() for the actual register setting.
142
143 d) although PXA3xx MFP supports edge detection on each pin, the
144 internal logic will only wakeup the system when those specific bits
145 in ADxER registers are set, which can be well mapped to the
146 corresponding peripheral, thus set_irq_wake() can be called with
147 the peripheral IRQ to enable the wakeup.
148
149
150 MFP on PXA3xx
151===============
152
153Every external I/O pad on PXA3xx (excluding those for special purpose) has
154one MFP logic associated, and is controlled by one MFP register (MFPR).
155
156The MFPR has the following bit definitions (for PXA300/PXA310/PXA320):
157
158 31 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
159 +-------------------------+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
160 | RESERVED |PS|PU|PD| DRIVE |SS|SD|SO|EC|EF|ER|--| AF_SEL |
161 +-------------------------+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
162
163 Bit 3: RESERVED
164 Bit 4: EDGE_RISE_EN - enable detection of rising edge on this pin
165 Bit 5: EDGE_FALL_EN - enable detection of falling edge on this pin
166 Bit 6: EDGE_CLEAR - disable edge detection on this pin
167 Bit 7: SLEEP_OE_N - enable outputs during low power modes
168 Bit 8: SLEEP_DATA - output data on the pin during low power modes
169 Bit 9: SLEEP_SEL - selection control for low power modes signals
170 Bit 13: PULLDOWN_EN - enable the internal pull-down resistor on this pin
171 Bit 14: PULLUP_EN - enable the internal pull-up resistor on this pin
172 Bit 15: PULL_SEL - pull state controlled by selected alternate function
173 (0) or by PULL{UP,DOWN}_EN bits (1)
174
175 Bit 0 - 2: AF_SEL - alternate function selection, 8 possibilities, from 0-7
176 Bit 10-12: DRIVE - drive strength and slew rate
177 0b000 - fast 1mA
178 0b001 - fast 2mA
179 0b002 - fast 3mA
180 0b003 - fast 4mA
181 0b004 - slow 6mA
182 0b005 - fast 6mA
183 0b006 - slow 10mA
184 0b007 - fast 10mA
185
186 MFP Design for PXA2xx/PXA3xx
187==============================
188
189Due to the difference of pin-mux handling between PXA2xx and PXA3xx, a unified
190MFP API is introduced to cover both series of processors.
191
192The basic idea of this design is to introduce definitions for all possible pin
193configurations, these definitions are processor and platform independent, and
194the actual API invoked to convert these definitions into register settings and
195make them effective there-after.
196
197 Files Involved
198 --------------
199
200 - arch/arm/mach-pxa/include/mach/mfp.h
201
202 for
203 1. Unified pin definitions - enum constants for all configurable pins
204 2. processor-neutral bit definitions for a possible MFP configuration
205
206 - arch/arm/mach-pxa/include/mach/mfp-pxa3xx.h
207
208 for PXA3xx specific MFPR register bit definitions and PXA3xx common pin
209 configurations
210
211 - arch/arm/mach-pxa/include/mach/mfp-pxa2xx.h
212
213 for PXA2xx specific definitions and PXA25x/PXA27x common pin configurations
214
215 - arch/arm/mach-pxa/include/mach/mfp-pxa25x.h
216 arch/arm/mach-pxa/include/mach/mfp-pxa27x.h
217 arch/arm/mach-pxa/include/mach/mfp-pxa300.h
218 arch/arm/mach-pxa/include/mach/mfp-pxa320.h
219 arch/arm/mach-pxa/include/mach/mfp-pxa930.h
220
221 for processor specific definitions
222
223 - arch/arm/mach-pxa/mfp-pxa3xx.c
224 - arch/arm/mach-pxa/mfp-pxa2xx.c
225
226 for implementation of the pin configuration to take effect for the actual
227 processor.
228
229 Pin Configuration
230 -----------------
231
232 The following comments are copied from mfp.h (see the actual source code
233 for most updated info)
234
235 /*
236 * a possible MFP configuration is represented by a 32-bit integer
237 *
238 * bit 0.. 9 - MFP Pin Number (1024 Pins Maximum)
239 * bit 10..12 - Alternate Function Selection
240 * bit 13..15 - Drive Strength
241 * bit 16..18 - Low Power Mode State
242 * bit 19..20 - Low Power Mode Edge Detection
243 * bit 21..22 - Run Mode Pull State
244 *
245 * to facilitate the definition, the following macros are provided
246 *
247 * MFP_CFG_DEFAULT - default MFP configuration value, with
248 * alternate function = 0,
249 * drive strength = fast 3mA (MFP_DS03X)
250 * low power mode = default
251 * edge detection = none
252 *
253 * MFP_CFG - default MFPR value with alternate function
254 * MFP_CFG_DRV - default MFPR value with alternate function and
255 * pin drive strength
256 * MFP_CFG_LPM - default MFPR value with alternate function and
257 * low power mode
258 * MFP_CFG_X - default MFPR value with alternate function,
259 * pin drive strength and low power mode
260 */
261
262 Examples of pin configurations are:
263
264 #define GPIO94_SSP3_RXD MFP_CFG_X(GPIO94, AF1, DS08X, FLOAT)
265
266 which reads GPIO94 can be configured as SSP3_RXD, with alternate function
267 selection of 1, driving strength of 0b101, and a float state in low power
268 modes.
269
270 NOTE: this is the default setting of this pin being configured as SSP3_RXD
271 which can be modified a bit in board code, though it is not recommended to
272 do so, simply because this default setting is usually carefully encoded,
273 and is supposed to work in most cases.
274
275 Register Settings
276 -----------------
277
278 Register settings on PXA3xx for a pin configuration is actually very
279 straight-forward, most bits can be converted directly into MFPR value
280 in a easier way. Two sets of MFPR values are calculated: the run-time
281 ones and the low power mode ones, to allow different settings.
282
283 The conversion from a generic pin configuration to the actual register
284 settings on PXA2xx is a bit complicated: many registers are involved,
285 including GAFRx, GPDRx, PGSRx, PWER, PKWR, PFER and PRER. Please see
286 mfp-pxa2xx.c for how the conversion is made.