gpio: idio-16: Introduce the ACCES IDIO-16 GPIO library module

Exposes consumer library functions to facilitate communication with
devices within the ACCES IDIO-16 family such as the 104-IDIO-16 and
the PCI-IDIO-16.

A CONFIG_GPIO_IDIO_16 Kconfig option is introduced by this patch.
Modules wanting access to these idio-16 library functions should select
this Kconfig option and import the GPIO_IDIO_16 symbol namespace.

Cc: Andy Shevchenko <andriy.shevchenko@intel.com>
Signed-off-by: William Breathitt Gray <william.gray@linaro.org>
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>

5 files changed, 234 insertions, 0 deletions

diff --git a/MAINTAINERS b/MAINTAINERS
index cf0f18502372..74efa0492c43 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -312,6 +312,13 @@ L:	linux-iio@vger.kernel.org
 S:	Maintained
 F:	drivers/counter/104-quad-8.c
 
+ACCES IDIO-16 GPIO LIBRARY
+M:	William Breathitt Gray <william.gray@linaro.org>
+L:	linux-gpio@vger.kernel.org
+S:	Maintained
+F:	drivers/gpio/gpio-idio-16.c
+F:	drivers/gpio/gpio-idio-16.h
+
 ACCES PCI-IDIO-16 GPIO DRIVER
 M:	William Breathitt Gray <william.gray@linaro.org>
 L:	linux-gpio@vger.kernel.org
diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig
index e034f752e7ce..3f8cf6e2165e 100644
--- a/drivers/gpio/Kconfig
+++ b/drivers/gpio/Kconfig
@@ -109,6 +109,15 @@ config GPIO_REGMAP
 config GPIO_MAX730X
 	tristate
 
+config GPIO_IDIO_16
+	tristate
+	help
+	  Enables support for the idio-16 library functions. The idio-16 library
+	  provides functions to facilitate communication with devices within the
+	  ACCES IDIO-16 family such as the 104-IDIO-16 and the PCI-IDIO-16.
+
+	  If built as a module its name will be gpio-idio-16.
+
 menu "Memory mapped GPIO drivers"
 	depends on HAS_IOMEM
 
diff --git a/drivers/gpio/Makefile b/drivers/gpio/Makefile
index 84fae267e8eb..37a0b7ebda43 100644
--- a/drivers/gpio/Makefile
+++ b/drivers/gpio/Makefile
@@ -68,6 +68,7 @@ obj-$(CONFIG_GPIO_HLWD)			+= gpio-hlwd.o
 obj-$(CONFIG_HTC_EGPIO)			+= gpio-htc-egpio.o
 obj-$(CONFIG_GPIO_I8255)		+= gpio-i8255.o
 obj-$(CONFIG_GPIO_ICH)			+= gpio-ich.o
+obj-$(CONFIG_GPIO_IDIO_16)		+= gpio-idio-16.o
 obj-$(CONFIG_GPIO_IDT3243X)		+= gpio-idt3243x.o
 obj-$(CONFIG_GPIO_IMX_SCU)		+= gpio-imx-scu.o
 obj-$(CONFIG_GPIO_IOP)			+= gpio-iop.o
diff --git a/drivers/gpio/gpio-idio-16.c b/drivers/gpio/gpio-idio-16.c
new file mode 100644
index 000000000000..13315242d220
--- /dev/null
+++ b/drivers/gpio/gpio-idio-16.c
@@ -0,0 +1,146 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * GPIO library for the ACCES IDIO-16 family
+ * Copyright (C) 2022 William Breathitt Gray
+ */
+#include <linux/bitmap.h>
+#include <linux/export.h>
+#include <linux/io.h>
+#include <linux/module.h>
+#include <linux/spinlock.h>
+#include <linux/types.h>
+
+#include "gpio-idio-16.h"
+
+#define DEFAULT_SYMBOL_NAMESPACE GPIO_IDIO_16
+
+/**
+ * idio_16_get - get signal value at signal offset
+ * @reg:	ACCES IDIO-16 device registers
+ * @state:	ACCES IDIO-16 device state
+ * @offset:	offset of signal to get
+ *
+ * Returns the signal value (0=low, 1=high) for the signal at @offset.
+ */
+int idio_16_get(struct idio_16 __iomem *const reg,
+		struct idio_16_state *const state, const unsigned long offset)
+{
+	const unsigned long mask = BIT(offset);
+
+	if (offset < IDIO_16_NOUT)
+		return test_bit(offset, state->out_state);
+
+	if (offset < 24)
+		return !!(ioread8(&reg->in0_7) & (mask >> IDIO_16_NOUT));
+
+	if (offset < 32)
+		return !!(ioread8(&reg->in8_15) & (mask >> 24));
+
+	return -EINVAL;
+}
+EXPORT_SYMBOL_GPL(idio_16_get);
+
+/**
+ * idio_16_get_multiple - get multiple signal values at multiple signal offsets
+ * @reg:	ACCES IDIO-16 device registers
+ * @state:	ACCES IDIO-16 device state
+ * @mask:	mask of signals to get
+ * @bits:	bitmap to store signal values
+ *
+ * Stores in @bits the values (0=low, 1=high) for the signals defined by @mask.
+ */
+void idio_16_get_multiple(struct idio_16 __iomem *const reg,
+			  struct idio_16_state *const state,
+			  const unsigned long *const mask,
+			  unsigned long *const bits)
+{
+	unsigned long flags;
+	const unsigned long out_mask = GENMASK(IDIO_16_NOUT - 1, 0);
+
+	spin_lock_irqsave(&state->lock, flags);
+
+	bitmap_replace(bits, bits, state->out_state, &out_mask, IDIO_16_NOUT);
+	if (*mask & GENMASK(23, 16))
+		bitmap_set_value8(bits, ioread8(&reg->in0_7), 16);
+	if (*mask & GENMASK(31, 24))
+		bitmap_set_value8(bits, ioread8(&reg->in8_15), 24);
+
+	spin_unlock_irqrestore(&state->lock, flags);
+}
+EXPORT_SYMBOL_GPL(idio_16_get_multiple);
+
+/**
+ * idio_16_set - set signal value at signal offset
+ * @reg:	ACCES IDIO-16 device registers
+ * @state:	ACCES IDIO-16 device state
+ * @offset:	offset of signal to set
+ * @value:	value of signal to set
+ *
+ * Assigns output @value for the signal at @offset.
+ */
+void idio_16_set(struct idio_16 __iomem *const reg,
+		 struct idio_16_state *const state, const unsigned long offset,
+		 const unsigned long value)
+{
+	unsigned long flags;
+
+	if (offset >= IDIO_16_NOUT)
+		return;
+
+	spin_lock_irqsave(&state->lock, flags);
+
+	__assign_bit(offset, state->out_state, value);
+	if (offset < 8)
+		iowrite8(bitmap_get_value8(state->out_state, 0), &reg->out0_7);
+	else
+		iowrite8(bitmap_get_value8(state->out_state, 8), &reg->out8_15);
+
+	spin_unlock_irqrestore(&state->lock, flags);
+}
+EXPORT_SYMBOL_GPL(idio_16_set);
+
+/**
+ * idio_16_set_multiple - set signal values at multiple signal offsets
+ * @reg:	ACCES IDIO-16 device registers
+ * @state:	ACCES IDIO-16 device state
+ * @mask:	mask of signals to set
+ * @bits:	bitmap of signal output values
+ *
+ * Assigns output values defined by @bits for the signals defined by @mask.
+ */
+void idio_16_set_multiple(struct idio_16 __iomem *const reg,
+			  struct idio_16_state *const state,
+			  const unsigned long *const mask,
+			  const unsigned long *const bits)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&state->lock, flags);
+
+	bitmap_replace(state->out_state, state->out_state, bits, mask,
+		       IDIO_16_NOUT);
+	if (*mask & GENMASK(7, 0))
+		iowrite8(bitmap_get_value8(state->out_state, 0), &reg->out0_7);
+	if (*mask & GENMASK(15, 8))
+		iowrite8(bitmap_get_value8(state->out_state, 8), &reg->out8_15);
+
+	spin_unlock_irqrestore(&state->lock, flags);
+}
+EXPORT_SYMBOL_GPL(idio_16_set_multiple);
+
+/**
+ * idio_16_state_init - initialize idio_16_state structure
+ * @state:	ACCES IDIO-16 device state
+ *
+ * Initializes the ACCES IDIO-16 device @state for use in idio-16 library
+ * functions.
+ */
+void idio_16_state_init(struct idio_16_state *const state)
+{
+	spin_lock_init(&state->lock);
+}
+EXPORT_SYMBOL_GPL(idio_16_state_init);
+
+MODULE_AUTHOR("William Breathitt Gray");
+MODULE_DESCRIPTION("ACCES IDIO-16 GPIO Library");
+MODULE_LICENSE("GPL");
diff --git a/drivers/gpio/gpio-idio-16.h b/drivers/gpio/gpio-idio-16.h
new file mode 100644
index 000000000000..928f8251a2bd
--- /dev/null
+++ b/drivers/gpio/gpio-idio-16.h
@@ -0,0 +1,71 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/* Copyright 2022 William Breathitt Gray */
+#ifndef _IDIO_16_H_
+#define _IDIO_16_H_
+
+#include <linux/spinlock.h>
+#include <linux/types.h>
+
+/**
+ * struct idio_16 - IDIO-16 registers structure
+ * @out0_7:	Read: FET Drive Outputs 0-7
+ *		Write: FET Drive Outputs 0-7
+ * @in0_7:	Read: Isolated Inputs 0-7
+ *		Write: Clear Interrupt
+ * @irq_ctl:	Read: Enable IRQ
+ *		Write: Disable IRQ
+ * @filter_ctl:	Read: Activate Input Filters 0-15
+ *		Write: Deactivate Input Filters 0-15
+ * @out8_15:	Read: FET Drive Outputs 8-15
+ *		Write: FET Drive Outputs 8-15
+ * @in8_15:	Read: Isolated Inputs 8-15
+ *		Write: Unused
+ * @irq_status:	Read: Interrupt status
+ *		Write: Unused
+ */
+struct idio_16 {
+	u8 out0_7;
+	u8 in0_7;
+	u8 irq_ctl;
+	u8 filter_ctl;
+	u8 out8_15;
+	u8 in8_15;
+	u8 irq_status;
+};
+
+#define IDIO_16_NOUT 16
+
+/**
+ * struct idio_16_state - IDIO-16 state structure
+ * @lock:	synchronization lock for accessing device state
+ * @out_state:	output signals state
+ */
+struct idio_16_state {
+	spinlock_t lock;
+	DECLARE_BITMAP(out_state, IDIO_16_NOUT);
+};
+
+/**
+ * idio_16_get_direction - get the I/O direction for a signal offset
+ * @offset:	offset of signal to get direction
+ *
+ * Returns the signal direction (0=output, 1=input) for the signal at @offset.
+ */
+static inline int idio_16_get_direction(const unsigned long offset)
+{
+	return (offset >= IDIO_16_NOUT) ? 1 : 0;
+}
+
+int idio_16_get(struct idio_16 __iomem *reg, struct idio_16_state *state,
+		unsigned long offset);
+void idio_16_get_multiple(struct idio_16 __iomem *reg,
+			  struct idio_16_state *state,
+			  const unsigned long *mask, unsigned long *bits);
+void idio_16_set(struct idio_16 __iomem *reg, struct idio_16_state *state,
+		 unsigned long offset, unsigned long value);
+void idio_16_set_multiple(struct idio_16 __iomem *reg,
+			  struct idio_16_state *state,
+			  const unsigned long *mask, const unsigned long *bits);
+void idio_16_state_init(struct idio_16_state *state);
+
+#endif /* _IDIO_16_H_ */