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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); | |
47 | RSR_CPENABLE(*cpenable); | |
48 | WSR_CPENABLE(*cpenable | BIT(XCHAL_CP_ID_XTIOP)); | |
49 | ||
50 | return flags; | |
51 | } | |
52 | ||
53 | static inline void disable_cp(unsigned long flags, unsigned long cpenable) | |
54 | { | |
55 | WSR_CPENABLE(cpenable); | |
56 | local_irq_restore(flags); | |
57 | } | |
58 | ||
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59 | #else |
60 | ||
61 | static inline unsigned long enable_cp(unsigned long *cpenable) | |
62 | { | |
63 | *cpenable = 0; /* avoid uninitialized value warning */ | |
64 | return 0; | |
65 | } | |
66 | ||
67 | static inline void disable_cp(unsigned long flags, unsigned long cpenable) | |
68 | { | |
69 | } | |
70 | ||
71 | #endif /* XCHAL_HAVE_CP */ | |
72 | ||
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73 | static int xtensa_impwire_get_direction(struct gpio_chip *gc, unsigned offset) |
74 | { | |
75 | return 1; /* input only */ | |
76 | } | |
77 | ||
78 | static int xtensa_impwire_get_value(struct gpio_chip *gc, unsigned offset) | |
79 | { | |
80 | unsigned long flags, saved_cpenable; | |
81 | u32 impwire; | |
82 | ||
83 | flags = enable_cp(&saved_cpenable); | |
84 | __asm__ __volatile__("read_impwire %0" : "=a" (impwire)); | |
85 | disable_cp(flags, saved_cpenable); | |
86 | ||
87 | return !!(impwire & BIT(offset)); | |
88 | } | |
89 | ||
90 | static void xtensa_impwire_set_value(struct gpio_chip *gc, unsigned offset, | |
91 | int value) | |
92 | { | |
93 | BUG(); /* output only; should never be called */ | |
94 | } | |
95 | ||
96 | static int xtensa_expstate_get_direction(struct gpio_chip *gc, unsigned offset) | |
97 | { | |
98 | return 0; /* output only */ | |
99 | } | |
100 | ||
101 | static int xtensa_expstate_get_value(struct gpio_chip *gc, unsigned offset) | |
102 | { | |
103 | unsigned long flags, saved_cpenable; | |
104 | u32 expstate; | |
105 | ||
106 | flags = enable_cp(&saved_cpenable); | |
107 | __asm__ __volatile__("rur.expstate %0" : "=a" (expstate)); | |
108 | disable_cp(flags, saved_cpenable); | |
109 | ||
110 | return !!(expstate & BIT(offset)); | |
111 | } | |
112 | ||
113 | static void xtensa_expstate_set_value(struct gpio_chip *gc, unsigned offset, | |
114 | int value) | |
115 | { | |
116 | unsigned long flags, saved_cpenable; | |
117 | u32 mask = BIT(offset); | |
118 | u32 val = value ? BIT(offset) : 0; | |
119 | ||
120 | flags = enable_cp(&saved_cpenable); | |
121 | __asm__ __volatile__("wrmsk_expstate %0, %1" | |
122 | :: "a" (val), "a" (mask)); | |
123 | disable_cp(flags, saved_cpenable); | |
124 | } | |
125 | ||
126 | static struct gpio_chip impwire_chip = { | |
127 | .label = "impwire", | |
128 | .base = -1, | |
129 | .ngpio = 32, | |
130 | .get_direction = xtensa_impwire_get_direction, | |
131 | .get = xtensa_impwire_get_value, | |
132 | .set = xtensa_impwire_set_value, | |
133 | }; | |
134 | ||
135 | static struct gpio_chip expstate_chip = { | |
136 | .label = "expstate", | |
137 | .base = -1, | |
138 | .ngpio = 32, | |
139 | .get_direction = xtensa_expstate_get_direction, | |
140 | .get = xtensa_expstate_get_value, | |
141 | .set = xtensa_expstate_set_value, | |
142 | }; | |
143 | ||
144 | static int xtensa_gpio_probe(struct platform_device *pdev) | |
145 | { | |
146 | int ret; | |
147 | ||
4eab22e7 | 148 | ret = gpiochip_add_data(&impwire_chip, NULL); |
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149 | if (ret) |
150 | return ret; | |
4eab22e7 | 151 | return gpiochip_add_data(&expstate_chip, NULL); |
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152 | } |
153 | ||
154 | static struct platform_driver xtensa_gpio_driver = { | |
155 | .driver = { | |
156 | .name = "xtensa-gpio", | |
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157 | }, |
158 | .probe = xtensa_gpio_probe, | |
159 | }; | |
160 | ||
161 | static int __init xtensa_gpio_init(void) | |
162 | { | |
163 | struct platform_device *pdev; | |
164 | ||
165 | pdev = platform_device_register_simple("xtensa-gpio", 0, NULL, 0); | |
166 | if (IS_ERR(pdev)) | |
167 | return PTR_ERR(pdev); | |
168 | ||
169 | return platform_driver_register(&xtensa_gpio_driver); | |
170 | } | |
171 | device_initcall(xtensa_gpio_init); | |
172 | ||
173 | MODULE_AUTHOR("Baruch Siach <baruch@tkos.co.il>"); | |
174 | MODULE_DESCRIPTION("Xtensa LX4 GPIO32 driver"); | |
175 | MODULE_LICENSE("GPL"); |