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3edc6883 | 1 | // SPDX-License-Identifier: GPL-2.0 |
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2 | /* |
3 | * Copyright (C) 2013 TangoTec Ltd. | |
4 | * Author: Baruch Siach <baruch@tkos.co.il> | |
5 | * | |
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6 | * Driver for the Xtensa LX4 GPIO32 Option |
7 | * | |
8 | * Documentation: Xtensa LX4 Microprocessor Data Book, Section 2.22 | |
9 | * | |
10 | * GPIO32 is a standard optional extension to the Xtensa architecture core that | |
11 | * provides preconfigured output and input ports for intra SoC signaling. The | |
12 | * GPIO32 option is implemented as 32bit Tensilica Instruction Extension (TIE) | |
13 | * output state called EXPSTATE, and 32bit input wire called IMPWIRE. This | |
14 | * driver treats input and output states as two distinct devices. | |
15 | * | |
16 | * Access to GPIO32 specific instructions is controlled by the CPENABLE | |
17 | * (Coprocessor Enable Bits) register. By default Xtensa Linux startup code | |
18 | * disables access to all coprocessors. This driver sets the CPENABLE bit | |
19 | * corresponding to GPIO32 before any GPIO32 specific instruction, and restores | |
20 | * CPENABLE state after that. | |
21 | * | |
22 | * This driver is currently incompatible with SMP. The GPIO32 extension is not | |
23 | * guaranteed to be available in all cores. Moreover, each core controls a | |
24 | * different set of IO wires. A theoretical SMP aware version of this driver | |
25 | * would need to have a per core workqueue to do the actual GPIO manipulation. | |
26 | */ | |
27 | ||
28 | #include <linux/err.h> | |
29 | #include <linux/module.h> | |
83a4e2c5 | 30 | #include <linux/gpio/driver.h> |
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31 | #include <linux/bitops.h> |
32 | #include <linux/platform_device.h> | |
33 | ||
34 | #include <asm/coprocessor.h> /* CPENABLE read/write macros */ | |
35 | ||
36 | #ifndef XCHAL_CP_ID_XTIOP | |
37 | #error GPIO32 option is not enabled for your xtensa core variant | |
38 | #endif | |
39 | ||
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40 | #if XCHAL_HAVE_CP |
41 | ||
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42 | static inline unsigned long enable_cp(unsigned long *cpenable) |
43 | { | |
44 | unsigned long flags; | |
45 | ||
46 | local_irq_save(flags); | |
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47 | *cpenable = xtensa_get_sr(cpenable); |
48 | xtensa_set_sr(*cpenable | BIT(XCHAL_CP_ID_XTIOP), cpenable); | |
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49 | return flags; |
50 | } | |
51 | ||
52 | static inline void disable_cp(unsigned long flags, unsigned long cpenable) | |
53 | { | |
634f0348 | 54 | xtensa_set_sr(cpenable, cpenable); |
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55 | local_irq_restore(flags); |
56 | } | |
57 | ||
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58 | #else |
59 | ||
60 | static inline unsigned long enable_cp(unsigned long *cpenable) | |
61 | { | |
62 | *cpenable = 0; /* avoid uninitialized value warning */ | |
63 | return 0; | |
64 | } | |
65 | ||
66 | static inline void disable_cp(unsigned long flags, unsigned long cpenable) | |
67 | { | |
68 | } | |
69 | ||
70 | #endif /* XCHAL_HAVE_CP */ | |
71 | ||
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72 | static int xtensa_impwire_get_direction(struct gpio_chip *gc, unsigned offset) |
73 | { | |
e42615ec | 74 | return GPIO_LINE_DIRECTION_IN; /* input only */ |
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75 | } |
76 | ||
77 | static int xtensa_impwire_get_value(struct gpio_chip *gc, unsigned offset) | |
78 | { | |
79 | unsigned long flags, saved_cpenable; | |
80 | u32 impwire; | |
81 | ||
82 | flags = enable_cp(&saved_cpenable); | |
83 | __asm__ __volatile__("read_impwire %0" : "=a" (impwire)); | |
84 | disable_cp(flags, saved_cpenable); | |
85 | ||
86 | return !!(impwire & BIT(offset)); | |
87 | } | |
88 | ||
89 | static void xtensa_impwire_set_value(struct gpio_chip *gc, unsigned offset, | |
90 | int value) | |
91 | { | |
92 | BUG(); /* output only; should never be called */ | |
93 | } | |
94 | ||
95 | static int xtensa_expstate_get_direction(struct gpio_chip *gc, unsigned offset) | |
96 | { | |
e42615ec | 97 | return GPIO_LINE_DIRECTION_OUT; /* output only */ |
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98 | } |
99 | ||
100 | static int xtensa_expstate_get_value(struct gpio_chip *gc, unsigned offset) | |
101 | { | |
102 | unsigned long flags, saved_cpenable; | |
103 | u32 expstate; | |
104 | ||
105 | flags = enable_cp(&saved_cpenable); | |
106 | __asm__ __volatile__("rur.expstate %0" : "=a" (expstate)); | |
107 | disable_cp(flags, saved_cpenable); | |
108 | ||
109 | return !!(expstate & BIT(offset)); | |
110 | } | |
111 | ||
112 | static void xtensa_expstate_set_value(struct gpio_chip *gc, unsigned offset, | |
113 | int value) | |
114 | { | |
115 | unsigned long flags, saved_cpenable; | |
116 | u32 mask = BIT(offset); | |
117 | u32 val = value ? BIT(offset) : 0; | |
118 | ||
119 | flags = enable_cp(&saved_cpenable); | |
120 | __asm__ __volatile__("wrmsk_expstate %0, %1" | |
121 | :: "a" (val), "a" (mask)); | |
122 | disable_cp(flags, saved_cpenable); | |
123 | } | |
124 | ||
125 | static struct gpio_chip impwire_chip = { | |
126 | .label = "impwire", | |
127 | .base = -1, | |
128 | .ngpio = 32, | |
129 | .get_direction = xtensa_impwire_get_direction, | |
130 | .get = xtensa_impwire_get_value, | |
131 | .set = xtensa_impwire_set_value, | |
132 | }; | |
133 | ||
134 | static struct gpio_chip expstate_chip = { | |
135 | .label = "expstate", | |
136 | .base = -1, | |
137 | .ngpio = 32, | |
138 | .get_direction = xtensa_expstate_get_direction, | |
139 | .get = xtensa_expstate_get_value, | |
140 | .set = xtensa_expstate_set_value, | |
141 | }; | |
142 | ||
143 | static int xtensa_gpio_probe(struct platform_device *pdev) | |
144 | { | |
145 | int ret; | |
146 | ||
4eab22e7 | 147 | ret = gpiochip_add_data(&impwire_chip, NULL); |
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148 | if (ret) |
149 | return ret; | |
4eab22e7 | 150 | return gpiochip_add_data(&expstate_chip, NULL); |
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151 | } |
152 | ||
153 | static struct platform_driver xtensa_gpio_driver = { | |
154 | .driver = { | |
155 | .name = "xtensa-gpio", | |
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156 | }, |
157 | .probe = xtensa_gpio_probe, | |
158 | }; | |
159 | ||
160 | static int __init xtensa_gpio_init(void) | |
161 | { | |
162 | struct platform_device *pdev; | |
163 | ||
164 | pdev = platform_device_register_simple("xtensa-gpio", 0, NULL, 0); | |
165 | if (IS_ERR(pdev)) | |
166 | return PTR_ERR(pdev); | |
167 | ||
168 | return platform_driver_register(&xtensa_gpio_driver); | |
169 | } | |
170 | device_initcall(xtensa_gpio_init); | |
171 | ||
172 | MODULE_AUTHOR("Baruch Siach <baruch@tkos.co.il>"); | |
173 | MODULE_DESCRIPTION("Xtensa LX4 GPIO32 driver"); | |
174 | MODULE_LICENSE("GPL"); |