1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * Copyright (C) 2013 TangoTec Ltd.
4 * Author: Baruch Siach <baruch@tkos.co.il>
5 *
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>
30 #include <linux/gpio/driver.h>
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
40 #if XCHAL_HAVE_CP
41
enable_cp(unsigned long * cpenable)42 static inline unsigned long enable_cp(unsigned long *cpenable)
43 {
44 unsigned long flags;
45
46 local_irq_save(flags);
47 *cpenable = xtensa_get_sr(cpenable);
48 xtensa_set_sr(*cpenable | BIT(XCHAL_CP_ID_XTIOP), cpenable);
49 return flags;
50 }
51
disable_cp(unsigned long flags,unsigned long cpenable)52 static inline void disable_cp(unsigned long flags, unsigned long cpenable)
53 {
54 xtensa_set_sr(cpenable, cpenable);
55 local_irq_restore(flags);
56 }
57
58 #else
59
enable_cp(unsigned long * cpenable)60 static inline unsigned long enable_cp(unsigned long *cpenable)
61 {
62 *cpenable = 0; /* avoid uninitialized value warning */
63 return 0;
64 }
65
disable_cp(unsigned long flags,unsigned long cpenable)66 static inline void disable_cp(unsigned long flags, unsigned long cpenable)
67 {
68 }
69
70 #endif /* XCHAL_HAVE_CP */
71
xtensa_impwire_get_direction(struct gpio_chip * gc,unsigned offset)72 static int xtensa_impwire_get_direction(struct gpio_chip *gc, unsigned offset)
73 {
74 return 1; /* input only */
75 }
76
xtensa_impwire_get_value(struct gpio_chip * gc,unsigned offset)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
xtensa_impwire_set_value(struct gpio_chip * gc,unsigned offset,int value)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
xtensa_expstate_get_direction(struct gpio_chip * gc,unsigned offset)95 static int xtensa_expstate_get_direction(struct gpio_chip *gc, unsigned offset)
96 {
97 return 0; /* output only */
98 }
99
xtensa_expstate_get_value(struct gpio_chip * gc,unsigned offset)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
xtensa_expstate_set_value(struct gpio_chip * gc,unsigned offset,int value)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
xtensa_gpio_probe(struct platform_device * pdev)143 static int xtensa_gpio_probe(struct platform_device *pdev)
144 {
145 int ret;
146
147 ret = gpiochip_add_data(&impwire_chip, NULL);
148 if (ret)
149 return ret;
150 return gpiochip_add_data(&expstate_chip, NULL);
151 }
152
153 static struct platform_driver xtensa_gpio_driver = {
154 .driver = {
155 .name = "xtensa-gpio",
156 },
157 .probe = xtensa_gpio_probe,
158 };
159
xtensa_gpio_init(void)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");
175