[PATCH net-next 09/12] gpio: tc956x: add TC956x/QPS615 support

[Alex Elder <elder@riscstar.com>]

Toshiba TC956x is an Ethernet-AVB/TSN bridge and is essentially
a small and highly-specialized SoC.  TC956x includes a GPIO block that
can be accessed, alongside several other peripherals, via two PCIe
endpoint functions.  The PCIe function driver creates an auxiliary
device for the GPIO block, and that device gets bound to this auxiliary
device driver.

Co-developed-by: Daniel Thompson <daniel@riscstar.com>
Signed-off-by: Daniel Thompson <daniel@riscstar.com>
Signed-off-by: Alex Elder <elder@riscstar.com>
---
 drivers/gpio/Kconfig       |  11 ++
 drivers/gpio/Makefile      |   1 +
 drivers/gpio/gpio-tc956x.c | 209 +++++++++++++++++++++++++++++++++++++
 3 files changed, 221 insertions(+)
 create mode 100644 drivers/gpio/gpio-tc956x.c

diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig
index 020e51e30317a..746cedea7e91d 100644
--- a/drivers/gpio/Kconfig
+++ b/drivers/gpio/Kconfig
@@ -1646,6 +1646,17 @@ config GPIO_TC3589X
 	  This enables support for the GPIOs found on the TC3589X
 	  I/O Expander.
 
+config GPIO_TC956X
+	tristate "Toshiba TC956X GPIO support"
+	depends on TOSHIBA_TC956X_PCI
+	default m if TOSHIBA_TC956X_PCI
+	help
+	  This enables support for the GPIO controller embedded in the Toshiba
+	  TC956X (and Qualcomm QPS615).  This device connects to the host
+	  via PCIe port, which is the upstream port on an internal PCIe
+	  switch.  On some platforms, a few of the GPIO lines are used to
+	  manage external resets.
+
 config GPIO_TIMBERDALE
 	bool "Support for timberdale GPIO IP"
 	depends on MFD_TIMBERDALE
diff --git a/drivers/gpio/Makefile b/drivers/gpio/Makefile
index b267598b517de..c3584e7cba9b4 100644
--- a/drivers/gpio/Makefile
+++ b/drivers/gpio/Makefile
@@ -178,6 +178,7 @@ obj-$(CONFIG_GPIO_SYSCON)		+= gpio-syscon.o
 obj-$(CONFIG_GPIO_TANGIER)		+= gpio-tangier.o
 obj-$(CONFIG_GPIO_TB10X)		+= gpio-tb10x.o
 obj-$(CONFIG_GPIO_TC3589X)		+= gpio-tc3589x.o
+obj-$(CONFIG_GPIO_TC956X)		+= gpio-tc956x.o
 obj-$(CONFIG_GPIO_TEGRA186)		+= gpio-tegra186.o
 obj-$(CONFIG_GPIO_TEGRA)		+= gpio-tegra.o
 obj-$(CONFIG_GPIO_THUNDERX)		+= gpio-thunderx.o
diff --git a/drivers/gpio/gpio-tc956x.c b/drivers/gpio/gpio-tc956x.c
new file mode 100644
index 0000000000000..12221d8f812d9
--- /dev/null
+++ b/drivers/gpio/gpio-tc956x.c
@@ -0,0 +1,209 @@
+// SPDX-License-Identifier: GPL-2.0
+
+/*
+ * Copyright (C) 2026 by RISCstar Solutions Corporation.  All rights reserved.
+ */
+
+/*
+ * The Toshiba TC956X implements a PCIe Gen 3 switch that connects an
+ * upstream x4 port to two downstream PCIe x2 ports.  It incorporates
+ * an internal endpoint on a internal PCIe port that implements two
+ * Synopsys XGMAC Ethernet interfaces.
+ *
+ * 35 GPIOs are also implemented by an embedded GPIO controller.  Three
+ * registers control the first 32 GPIOs (other than 20 and 21, which are
+ * reserved).  Three other registers control GPIOs 32 through 36. GPIOs
+ * 22-24, 27-28, 31, and 34 are treated as "input only".
+ *
+ * There is a TC956X PCI power controller driver that accesses the
+ * direction and output value registers for GPIOs 2 and 3.  These
+ * GPIOs control the reset signal for the two downstream PCIe ports.
+ * Their values will never change during operation of this driver, and
+ * this driver reserves these two GPIOS.
+ */
+
+#include <linux/auxiliary_bus.h>
+#include <linux/dev_printk.h>
+#include <linux/gpio/driver.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/regmap.h>
+
+#define DRIVER_NAME		"tc956x-gpio"
+
+#define TC956X_GPIO_COUNT	37	/* Number of GPIOs (20-21 reserved) */
+
+/* The GPIO offsets are relative to 0x1200 in TC956X SFR space */
+#define GPIO_IN0_OFFSET		0x00		/* Input value (0-31) */
+#define GPIO_EN0_OFFSET		0x08		/* 0: out; 1: in (0-31) */
+#define GPIO_OUT0_OFFSET	0x10		/* Output value (0-31) */
+
+#define GPIO_IN1_OFFSET		0x04		/* Input value (32-36) */
+#define GPIO_EN1_OFFSET		0x0c		/* 0: out; 1: in (32-36) */
+#define GPIO_OUT1_OFFSET	0x14		/* Output value (32-36) */
+
+/*
+ * struct tc956x_gpio - Information related to the embedded GPIO controller
+ * @chip:		GPIO chip structure
+ * @regmap:		MMIO register map for SFR GPIO region access
+ * @input_only:		Bitmap indicating which GPIOs are input-only
+ */
+struct tc956x_gpio {
+	struct gpio_chip chip;
+	struct regmap *regmap;
+	DECLARE_BITMAP(input_only, TC956X_GPIO_COUNT);
+};
+
+static int tc956x_gpio_get_direction(struct gpio_chip *gc, unsigned int offset)
+{
+	struct tc956x_gpio *gpio = gpiochip_get_data(gc);
+	u32 reg;
+	u32 val;
+
+	if (test_bit(offset, gpio->input_only))
+		return GPIO_LINE_DIRECTION_IN;
+
+	reg = offset < 32 ? GPIO_EN0_OFFSET : GPIO_EN1_OFFSET;
+
+	regmap_read(gpio->regmap, reg, &val);
+	if (val & BIT(offset % 32))
+		return GPIO_LINE_DIRECTION_IN;
+
+	return GPIO_LINE_DIRECTION_OUT;
+}
+
+static int tc956x_gpio_direction_input(struct gpio_chip *gc,
+				       unsigned int offset)
+{
+	u32 reg = offset < 32 ? GPIO_EN0_OFFSET : GPIO_EN1_OFFSET;
+	struct tc956x_gpio *gpio = gpiochip_get_data(gc);
+	u32 mask = BIT(offset % 32);
+
+	return regmap_update_bits(gpio->regmap, reg, mask, mask);
+}
+
+static int tc956x_gpio_direction_output(struct gpio_chip *gc,
+					unsigned int offset, int value)
+{
+	struct tc956x_gpio *gpio = gpiochip_get_data(gc);
+	u32 vreg;
+	u32 dreg;
+	u32 mask;
+
+	if (test_bit(offset, gpio->input_only))
+		return -EINVAL;
+
+	if (offset < 32) {
+		vreg = GPIO_OUT0_OFFSET;
+		dreg = GPIO_EN0_OFFSET;
+	} else {
+		vreg = GPIO_OUT1_OFFSET;
+		dreg = GPIO_EN1_OFFSET;
+	}
+	mask = BIT(offset % 32);
+
+	/* Set output value first, then direction */
+	regmap_update_bits(gpio->regmap, vreg, mask, value ? mask : 0);
+
+	return regmap_update_bits(gpio->regmap, dreg, mask, 0);
+}
+
+static int tc956x_gpio_get(struct gpio_chip *gc, unsigned int offset)
+{
+	u32 reg = offset < 32 ? GPIO_IN0_OFFSET : GPIO_IN1_OFFSET;
+	struct tc956x_gpio *gpio = gpiochip_get_data(gc);
+	u32 val;
+
+	regmap_read(gpio->regmap, reg, &val);
+
+	return val & BIT(offset % 32) ? 1 : 0;
+}
+
+static int tc956x_gpio_set(struct gpio_chip *gc, unsigned int offset, int value)
+{
+	u32 reg = offset < 32 ? GPIO_OUT0_OFFSET : GPIO_OUT1_OFFSET;
+	struct tc956x_gpio *gpio = gpiochip_get_data(gc);
+	u32 mask = BIT(offset % 32);
+
+	return regmap_update_bits(gpio->regmap, reg, mask, value ? mask : 0);
+}
+
+static int tc956x_gpio_init_valid_mask(struct gpio_chip *gc,
+				       unsigned long *valid_mask,
+				       unsigned int ngpios)
+{
+	/*
+	 * GPIOs 2 and 3 are used by the PCI power control driver, and
+	 * we don't allow them to be used.  GPIOs 20 and 21 are reserved
+	 * (and not usable).
+	 */
+	bitmap_fill(valid_mask, ngpios);
+	bitmap_clear(valid_mask, 2, 2);
+	bitmap_clear(valid_mask, 20, 2);
+
+	return 0;
+}
+
+static int tc956x_gpio_probe(struct auxiliary_device *adev,
+			     const struct auxiliary_device_id *id)
+{
+	struct device *dev = &adev->dev;
+	struct tc956x_gpio *gpio;
+	struct gpio_chip *gc;
+
+	if (!dev->platform_data)
+		return -EINVAL;
+
+	gpio = devm_kzalloc(dev, sizeof(*gpio), GFP_KERNEL);
+	if (!gpio)
+		return -ENOMEM;
+	gpio->regmap = dev->platform_data;
+
+	/* Mark GPIOs 22, 23, 24, 27, 28, 31, and 34 as input only */
+	bitmap_set(gpio->input_only, 22, 3);
+	bitmap_set(gpio->input_only, 27, 2);
+	set_bit(31, gpio->input_only);
+	set_bit(34, gpio->input_only);
+
+	gc = &gpio->chip;
+
+	gc->label = DRIVER_NAME;
+	gc->parent = dev->parent;
+
+	gc->get_direction = tc956x_gpio_get_direction;
+	gc->direction_input = tc956x_gpio_direction_input;
+	gc->direction_output = tc956x_gpio_direction_output;
+	gc->get = tc956x_gpio_get;
+	gc->set = tc956x_gpio_set;
+	gc->init_valid_mask = tc956x_gpio_init_valid_mask;
+
+	gc->base = -1;
+	gc->ngpio = TC956X_GPIO_COUNT;
+	gc->can_sleep = false;
+
+	dev_set_drvdata(dev, gpio);
+
+	return devm_gpiochip_add_data(dev, gc, gpio);
+}
+
+static const struct auxiliary_device_id tc956x_gpio_ids[] = {
+	{ .name = "tc956x_pci.tc9564-gpio", },
+	{ }
+};
+MODULE_DEVICE_TABLE(auxiliary, tc956x_gpio_ids);
+
+static struct auxiliary_driver tc956x_gpio_driver = {
+	.name		= DRIVER_NAME,
+	.probe          = tc956x_gpio_probe,
+	.id_table       = tc956x_gpio_ids,
+	.driver = {
+		.name		= DRIVER_NAME,
+		.owner		= THIS_MODULE,
+		.probe_type	= PROBE_PREFER_ASYNCHRONOUS,
+	},
+};
+module_auxiliary_driver(tc956x_gpio_driver);
+
+MODULE_DESCRIPTION("Toshiba TC956X PCIe GPIO Driver");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("auxiliary:" DRIVER_NAME);
-- 
2.51.0