/* * Copyright (C) 2013 TangoTec Ltd. * Author: Baruch Siach <baruch@tkos.co.il> * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License version 2 as * published by the Free Software Foundation. * * Driver for the Xtensa LX4 GPIO32 Option * * Documentation: Xtensa LX4 Microprocessor Data Book, Section 2.22 * * GPIO32 is a standard optional extension to the Xtensa architecture core that * provides preconfigured output and input ports for intra SoC signaling. The * GPIO32 option is implemented as 32bit Tensilica Instruction Extension (TIE) * output state called EXPSTATE, and 32bit input wire called IMPWIRE. This * driver treats input and output states as two distinct devices. * * Access to GPIO32 specific instructions is controlled by the CPENABLE * (Coprocessor Enable Bits) register. By default Xtensa Linux startup code * disables access to all coprocessors. This driver sets the CPENABLE bit * corresponding to GPIO32 before any GPIO32 specific instruction, and restores * CPENABLE state after that. * * This driver is currently incompatible with SMP. The GPIO32 extension is not * guaranteed to be available in all cores. Moreover, each core controls a * different set of IO wires. A theoretical SMP aware version of this driver * would need to have a per core workqueue to do the actual GPIO manipulation. */ #include <linux/err.h> #include <linux/module.h> #include <linux/gpio.h> #include <linux/bitops.h> #include <linux/platform_device.h> #include <asm/coprocessor.h> /* CPENABLE read/write macros */ #ifndef XCHAL_CP_ID_XTIOP #error GPIO32 option is not enabled for your xtensa core variant #endif #if XCHAL_HAVE_CP static inline unsigned long enable_cp(unsigned long *cpenable) { unsigned long flags; local_irq_save(flags); RSR_CPENABLE(*cpenable); WSR_CPENABLE(*cpenable | BIT(XCHAL_CP_ID_XTIOP)); return flags; } static inline void disable_cp(unsigned long flags, unsigned long cpenable) { WSR_CPENABLE(cpenable); local_irq_restore(flags); } #else static inline unsigned long enable_cp(unsigned long *cpenable) { *cpenable = 0; /* avoid uninitialized value warning */ return 0; } static inline void disable_cp(unsigned long flags, unsigned long cpenable) { } #endif /* XCHAL_HAVE_CP */ static int xtensa_impwire_get_direction(struct gpio_chip *gc, unsigned offset) { return 1; /* input only */ } static int xtensa_impwire_get_value(struct gpio_chip *gc, unsigned offset) { unsigned long flags, saved_cpenable; u32 impwire; flags = enable_cp(&saved_cpenable); __asm__ __volatile__("read_impwire %0" : "=a" (impwire)); disable_cp(flags, saved_cpenable); return !!(impwire & BIT(offset)); } static void xtensa_impwire_set_value(struct gpio_chip *gc, unsigned offset, int value) { BUG(); /* output only; should never be called */ } static int xtensa_expstate_get_direction(struct gpio_chip *gc, unsigned offset) { return 0; /* output only */ } static int xtensa_expstate_get_value(struct gpio_chip *gc, unsigned offset) { unsigned long flags, saved_cpenable; u32 expstate; flags = enable_cp(&saved_cpenable); __asm__ __volatile__("rur.expstate %0" : "=a" (expstate)); disable_cp(flags, saved_cpenable); return !!(expstate & BIT(offset)); } static void xtensa_expstate_set_value(struct gpio_chip *gc, unsigned offset, int value) { unsigned long flags, saved_cpenable; u32 mask = BIT(offset); u32 val = value ? BIT(offset) : 0; flags = enable_cp(&saved_cpenable); __asm__ __volatile__("wrmsk_expstate %0, %1" :: "a" (val), "a" (mask)); disable_cp(flags, saved_cpenable); } static struct gpio_chip impwire_chip = { .label = "impwire", .base = -1, .ngpio = 32, .get_direction = xtensa_impwire_get_direction, .get = xtensa_impwire_get_value, .set = xtensa_impwire_set_value, }; static struct gpio_chip expstate_chip = { .label = "expstate", .base = -1, .ngpio = 32, .get_direction = xtensa_expstate_get_direction, .get = xtensa_expstate_get_value, .set = xtensa_expstate_set_value, }; static int xtensa_gpio_probe(struct platform_device *pdev) { int ret; ret = gpiochip_add_data(&impwire_chip, NULL); if (ret) return ret; return gpiochip_add_data(&expstate_chip, NULL); } static struct platform_driver xtensa_gpio_driver = { .driver = { .name = "xtensa-gpio", }, .probe = xtensa_gpio_probe, }; static int __init xtensa_gpio_init(void) { struct platform_device *pdev; pdev = platform_device_register_simple("xtensa-gpio", 0, NULL, 0); if (IS_ERR(pdev)) return PTR_ERR(pdev); return platform_driver_register(&xtensa_gpio_driver); } device_initcall(xtensa_gpio_init); MODULE_AUTHOR("Baruch Siach <baruch@tkos.co.il>"); MODULE_DESCRIPTION("Xtensa LX4 GPIO32 driver"); MODULE_LICENSE("GPL");