drivers/gpio/gpio-xtensa.c

   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
  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
  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
  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
  72 static int xtensa_impwire_get_direction(struct gpio_chip *gc, unsigned offset)
  73 {
  74         return GPIO_LINE_DIRECTION_IN; /* input only */
  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 {
  97         return GPIO_LINE_DIRECTION_OUT; /* output only */
  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
 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
 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");