--- /dev/null
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Bitbanging driver for multiple I2C busses with shared SCL pin using the GPIO API
+ * Copyright (c) 2025 Markus Stockhausen <markus.stockhausen at gmx.de>
+ */
+
+#include <linux/i2c-algo-bit.h>
+#include <linux/gpio/consumer.h>
+#include <linux/mod_devicetable.h>
+#include <linux/mutex.h>
+#include <linux/platform_device.h>
+
+struct gpio_shared_ctx;
+
+struct gpio_shared_bus {
+ int num;
+ struct gpio_desc *sda;
+ struct i2c_adapter adap;
+ struct i2c_algo_bit_data bit_data;
+ struct gpio_shared_ctx *ctx;
+};
+
+#define GPIO_SHARED_MAX_BUS 4
+
+struct gpio_shared_ctx {
+ struct device *dev;
+ struct gpio_desc *scl;
+ struct mutex lock;
+ struct gpio_shared_bus bus[GPIO_SHARED_MAX_BUS];
+};
+
+static void gpio_shared_setsda(void *data, int state)
+{
+ struct gpio_shared_bus *bus = data;
+
+ gpiod_set_value_cansleep(bus->sda, state);
+}
+
+static void gpio_shared_setscl(void *data, int state)
+{
+ struct gpio_shared_bus *bus = data;
+ struct gpio_shared_ctx *ctx = bus->ctx;
+
+ gpiod_set_value_cansleep(ctx->scl, state);
+}
+
+static int gpio_shared_getsda(void *data)
+{
+ struct gpio_shared_bus *bus = data;
+
+ return gpiod_get_value_cansleep(bus->sda);
+}
+
+static int gpio_shared_getscl(void *data)
+{
+ struct gpio_shared_bus *bus = data;
+ struct gpio_shared_ctx *ctx = bus->ctx;
+
+ return gpiod_get_value_cansleep(ctx->scl);
+}
+
+static int gpio_shared_pre_xfer(struct i2c_adapter *adap)
+{
+ struct gpio_shared_bus *bus = container_of(adap, typeof(*bus), adap);
+ struct gpio_shared_ctx *ctx = bus->ctx;
+
+ mutex_lock(&ctx->lock);
+ dev_dbg(ctx->dev, "lock before transfer to bus %d\n", bus->num);
+
+ return 0;
+}
+
+static void gpio_shared_post_xfer(struct i2c_adapter *adap)
+{
+ struct gpio_shared_bus *bus = container_of(adap, typeof(*bus), adap);
+ struct gpio_shared_ctx *ctx = bus->ctx;
+
+ dev_dbg(ctx->dev, "unlock after transfer to bus %d\n", bus->num);
+ mutex_unlock(&ctx->lock);
+}
+
+static int gpio_shared_probe(struct platform_device *pdev)
+{
+ struct device *dev = &pdev->dev;
+ struct fwnode_handle *child;
+ struct gpio_shared_ctx *ctx;
+ int msecs, ret, bus_num = -1;
+
+ ctx = devm_kzalloc(dev, sizeof(*ctx), GFP_KERNEL);
+ if (!ctx)
+ return -ENOMEM;
+
+ ctx->dev = dev;
+ mutex_init(&ctx->lock);
+
+ ctx->scl = devm_gpiod_get(dev, "scl", GPIOD_OUT_HIGH_OPEN_DRAIN);
+ if (IS_ERR(ctx->scl))
+ return dev_err_probe(dev, PTR_ERR(ctx->scl), "shared SCL node not found\n");
+
+ if (device_get_child_node_count(dev) >= GPIO_SHARED_MAX_BUS)
+ return dev_err_probe(dev, -EINVAL, "Too many channels\n");
+
+ device_for_each_child_node(dev, child) {
+ struct gpio_shared_bus *bus = &ctx->bus[++bus_num];
+ struct i2c_adapter *adap = &bus->adap;
+ struct i2c_algo_bit_data *bit_data = &bus->bit_data;
+
+ bus->sda = devm_fwnode_gpiod_get(dev, child, "sda", GPIOD_OUT_HIGH_OPEN_DRAIN,
+ fwnode_get_name(child));
+ if (IS_ERR(bus->sda)) {
+ fwnode_handle_put(child);
+ dev_err(dev, "SDA node for bus %d not found\n", bus_num);
+ continue;
+ }
+
+ bus->num = bus_num;
+ bus->ctx = ctx;
+
+ bit_data->data = bus;
+ bit_data->setsda = gpio_shared_setsda;
+ bit_data->setscl = gpio_shared_setscl;
+ bit_data->pre_xfer = gpio_shared_pre_xfer;
+ bit_data->post_xfer = gpio_shared_post_xfer;
+
+ if (fwnode_property_read_u32(child, "i2c-gpio,delay-us", &bit_data->udelay))
+ bit_data->udelay = 5;
+ if (!fwnode_property_read_bool(child, "i2c-gpio,sda-output-only"))
+ bit_data->getsda = gpio_shared_getsda;
+ if (!device_property_read_bool(dev, "i2c-gpio,scl-output-only"))
+ bit_data->getscl = gpio_shared_getscl;
+
+ if (!device_property_read_u32(dev, "i2c-gpio,timeout-ms", &msecs))
+ bit_data->timeout = msecs_to_jiffies(msecs);
+ else
+ bit_data->timeout = HZ / 10; /* 100ms */
+
+ if (gpiod_cansleep(bus->sda) || gpiod_cansleep(ctx->scl))
+ dev_warn(dev, "Slow GPIO pins might wreak havoc into I2C/SMBus bus timing");
+ else
+ bit_data->can_do_atomic = true;
+
+ adap->owner = THIS_MODULE;
+ strscpy(adap->name, KBUILD_MODNAME, sizeof(adap->name));
+ adap->dev.parent = dev;
+ device_set_node(&adap->dev, child);
+ adap->algo_data = &bus->bit_data;
+ adap->class = I2C_CLASS_HWMON;
+
+ ret = i2c_bit_add_bus(adap);
+ if (ret)
+ return ret;
+
+ dev_info(dev, "shared I2C bus %u using lines %u (SDA) and %u (SCL) delay=%d\n",
+ bus_num, desc_to_gpio(bus->sda), desc_to_gpio(ctx->scl),
+ bit_data->udelay);
+ }
+
+ return 0;
+}
+
+static const struct of_device_id gpio_shared_of_match[] = {
+ { .compatible = "i2c-gpio-shared" },
+ {}
+};
+MODULE_DEVICE_TABLE(of, gpio_shared_of_match);
+
+static struct platform_driver gpio_shared_driver = {
+ .probe = gpio_shared_probe,
+ .driver = {
+ .name = "i2c-gpio-shared",
+ .of_match_table = gpio_shared_of_match,
+ },
+};
+
+module_platform_driver(gpio_shared_driver);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Markus Stockhausen <markus.stockhausen at gmx.de>");
+MODULE_DESCRIPTION("bitbanging multi I2C driver for shared SCL");
--- /dev/null
+From 9d2327c5f1ac63cb14af088a95eba110ab0c473e Mon Sep 17 00:00:00 2001
+From: Markus Stockhausen <markus.stockhausen@gmx.de>
+Date: Wed, 7 May 2025 09:47:24 -0400
+Subject: [PATCH] realtek: add i2c-gpio-shared driver
+
+Adds the Kconfig and Makefile settings to make the new driver available.
+
+Signed-off-by: Markus Stockhausen <markus.stockhausen@gmx.de>
+---
+ drivers/i2c/busses/Kconfig | 9 +++++++++
+ drivers/i2c/busses/Makefile | 1 +
+ 2 files changed, 10 insertions(+)
+
+--- a/drivers/i2c/busses/Kconfig
++++ b/drivers/i2c/busses/Kconfig
+@@ -683,6 +683,15 @@ config I2C_GPIO
+ This is a very simple bitbanging I2C driver utilizing the
+ arch-neutral GPIO API to control the SCL and SDA lines.
+
++config I2C_GPIO_SHARED
++ tristate "multiple GPIO-based bitbanging I2C with shared SCL"
++ depends on GPIOLIB || COMPILE_TEST
++ select I2C_ALGOBIT
++ help
++ This is an alternative of the I2C GPIO driver for devices with only
++ few GPIO pins where multiple busses with dedicated SDA lines share
++ a single SCL line.
++
+ config I2C_GPIO_FAULT_INJECTOR
+ bool "GPIO-based fault injector"
+ depends on I2C_GPIO
+--- a/drivers/i2c/busses/Makefile
++++ b/drivers/i2c/busses/Makefile
+@@ -67,6 +67,7 @@ obj-$(CONFIG_I2C_EG20T) += i2c-eg20t.o
+ obj-$(CONFIG_I2C_EMEV2) += i2c-emev2.o
+ obj-$(CONFIG_I2C_EXYNOS5) += i2c-exynos5.o
+ obj-$(CONFIG_I2C_GPIO) += i2c-gpio.o
++obj-$(CONFIG_I2C_GPIO_SHARED) += i2c-gpio-shared.o
+ obj-$(CONFIG_I2C_HIGHLANDER) += i2c-highlander.o
+ obj-$(CONFIG_I2C_HISI) += i2c-hisi.o
+ obj-$(CONFIG_I2C_HIX5HD2) += i2c-hix5hd2.o
projects / thirdparty / openwrt.git / commitdiff
