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         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
  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
  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
 148         ret = gpiochip_add_data(&impwire_chip, NULL);
 149         if (ret)
 150                 return ret;
 151         return gpiochip_add_data(&expstate_chip, NULL);
 152 }
 153
 154 static struct platform_driver xtensa_gpio_driver = {
 155         .driver         = {
 156                 .name           = "xtensa-gpio",
 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");