From 57f0f512b273f60d52568b8c6b77e17f5636edc0 Mon Sep 17 00:00:00 2001 From: André Fabian Silva Delgado Date: Wed, 5 Aug 2015 17:04:01 -0300 Subject: Initial import --- drivers/gpio/gpio-xtensa.c | 178 +++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 178 insertions(+) create mode 100644 drivers/gpio/gpio-xtensa.c (limited to 'drivers/gpio/gpio-xtensa.c') diff --git a/drivers/gpio/gpio-xtensa.c b/drivers/gpio/gpio-xtensa.c new file mode 100644 index 000000000..93ec95df6 --- /dev/null +++ b/drivers/gpio/gpio-xtensa.c @@ -0,0 +1,178 @@ +/* + * Copyright (C) 2013 TangoTec Ltd. + * Author: Baruch Siach + * + * 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 +#include +#include +#include +#include + +#include /* 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(&impwire_chip); + if (ret) + return ret; + return gpiochip_add(&expstate_chip); +} + +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 "); +MODULE_DESCRIPTION("Xtensa LX4 GPIO32 driver"); +MODULE_LICENSE("GPL"); -- cgit v1.2.3-54-g00ecf