1 files changed, 163 insertions, 0 deletions

diff --git a/drivers/gpio/gpio-xtensa.c b/drivers/gpio/gpio-xtensa.c
new file mode 100644
index 000000000000..1d136eceda62
--- /dev/null
+++ b/drivers/gpio/gpio-xtensa.c
@@ -0,0 +1,163 @@
+/*
+ * 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
+
+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);
+}
+
+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",
+                .owner          = THIS_MODULE,
+        },
+        .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");