@@ -21480,6 +21480,7 @@ M: Frank Zago <frank@zago.net>
L: linux-usb@vger.kernel.org
S: Maintained
F: drivers/gpio/gpio-ch341.c
+F: drivers/i2c/busses/i2c-ch341.c
F: drivers/mfd/ch341-core.c
F: include/linux/mfd/ch341.h
@@ -1199,6 +1199,16 @@ config I2C_RCAR
comment "External I2C/SMBus adapter drivers"
+config I2C_CH341
+ tristate "CH341 USB to I2C support"
+ select MFD_CH341
+ help
+ If you say yes to this option, I2C support will be included for the
+ WCH CH341, a USB to I2C/SPI/GPIO interface.
+
+ This driver can also be built as a module. If so, the module
+ will be called i2c-ch341.
+
config I2C_DIOLAN_U2C
tristate "Diolan U2C-12 USB adapter"
depends on USB
@@ -127,6 +127,7 @@ obj-$(CONFIG_I2C_XLP9XX) += i2c-xlp9xx.o
obj-$(CONFIG_I2C_RCAR) += i2c-rcar.o
# External I2C/SMBus adapter drivers
+obj-$(CONFIG_I2C_CH341) += i2c-ch341.o
obj-$(CONFIG_I2C_DIOLAN_U2C) += i2c-diolan-u2c.o
obj-$(CONFIG_I2C_DLN2) += i2c-dln2.o
obj-$(CONFIG_I2C_CP2615) += i2c-cp2615.o
new file mode 100644
@@ -0,0 +1,377 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * I2C cell driver for the CH341A, CH341B and CH341T.
+ *
+ * Copyright 2022, Frank Zago
+ * Copyright (c) 2016 Tse Lun Bien
+ * Copyright (c) 2014 Marco Gittler
+ * Copyright (C) 2006-2007 Till Harbaum (Till@Harbaum.org)
+ */
+
+#include <linux/i2c.h>
+#include <linux/kernel.h>
+#include <linux/mfd/ch341.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/types.h>
+#include <linux/usb.h>
+
+/* I2C bus speed. Speed selection is not implemented. */
+#define CH341_I2C_20KHZ 0
+#define CH341_I2C_100KHZ 1
+#define CH341_I2C_400KHZ 2
+#define CH341_I2C_750KHZ 3
+
+/* I2C chip commands */
+#define CH341_CMD_I2C_STREAM 0xAA
+#define CH341_CMD_I2C_STM_END 0x00
+
+#define CH341_CMD_I2C_STM_STA 0x74
+#define CH341_CMD_I2C_STM_STO 0x75
+#define CH341_CMD_I2C_STM_OUT 0x80
+#define CH341_CMD_I2C_STM_IN 0xC0
+#define CH341_CMD_I2C_STM_SET 0x60
+
+/*
+ * The maximum request size is 4096 bytes, both for reading and
+ * writing, split in up to 128 32-byte segments, which includes the
+ * CH341 commands and the I2C data.
+ */
+#define SEG_COUNT 128
+
+/*
+ * Limit the transfer size that can be written. 4KiB is the maximum
+ * size of the whole buffer, but it must include all the command
+ * delimiters. 3KiB sounds reasonable.
+ */
+#define MAX_RW_LENGTH 3072
+
+struct ch341_i2c {
+ struct i2c_adapter adapter;
+
+ /* I2C request and response state */
+ int idx_out; /* current offset in buf */
+ int out_seg; /* current segment */
+ u8 i2c_buf[SEG_COUNT * SEG_SIZE];
+};
+
+/*
+ * Special case the no data transfer (SMBUS quick message), since some
+ * parameters are a bit different than the normal case.
+ */
+static int no_data_xfer(struct i2c_adapter *adapter, const struct i2c_msg *msg)
+{
+ struct ch341_i2c *dev = i2c_get_adapdata(adapter);
+ struct ch341_ddata *ddata = adapter->algo_data;
+ u8 *out = dev->i2c_buf;
+ int actual;
+ int ret;
+
+ out[0] = CH341_CMD_I2C_STREAM;
+ out[1] = CH341_CMD_I2C_STM_STA;
+ out[2] = CH341_CMD_I2C_STM_OUT;
+ out[3] = msg->addr << 1 | (msg->flags & I2C_M_RD);
+ out[4] = CH341_CMD_I2C_STM_IN;
+ out[5] = CH341_CMD_I2C_STM_STO;
+ out[6] = CH341_CMD_I2C_STM_END;
+
+ mutex_lock(&ddata->usb_lock);
+
+ /* Issue the request */
+ ret = usb_bulk_msg(ddata->usb_dev,
+ usb_sndbulkpipe(ddata->usb_dev, ddata->ep_out),
+ dev->i2c_buf, 7, &actual, DEFAULT_TIMEOUT_MS);
+ if (ret < 0) {
+ mutex_unlock(&ddata->usb_lock);
+ return ret;
+ }
+
+ ret = usb_bulk_msg(ddata->usb_dev,
+ usb_rcvbulkpipe(ddata->usb_dev, ddata->ep_in),
+ dev->i2c_buf, 2, &actual,
+ DEFAULT_TIMEOUT_MS);
+ if (ret < 0) {
+ mutex_unlock(&ddata->usb_lock);
+ return ret;
+ }
+
+ mutex_unlock(&ddata->usb_lock);
+
+ if (actual != 2 || dev->i2c_buf[0] & 0x80)
+ return -ETIMEDOUT;
+
+ return 1;
+}
+
+/*
+ * Append a write command to the current request. A set of 32-byte
+ * packets is filled. Each packet starts with STREAM and finishes with
+ * END, and contains an OUT field, leaving up to 29 bytes of data. The
+ * first packet must also include a START and the device address.
+ */
+static int append_write(struct ch341_i2c *dev, const struct i2c_msg *msg)
+{
+ bool start_done = false;
+ u8 *out = dev->i2c_buf;
+ int len;
+ u8 *p;
+
+ len = msg->len;
+ p = msg->buf;
+
+ while (len) {
+ int to_write;
+ int avail;
+
+ if (dev->idx_out % SEG_SIZE) {
+ /* Finish current packet, and advance to the next one */
+ out[dev->idx_out++] = CH341_CMD_I2C_STM_END;
+ dev->out_seg++;
+ dev->idx_out = dev->out_seg * SEG_SIZE;
+
+ if (dev->out_seg == SEG_COUNT)
+ return -E2BIG;
+ }
+
+ out[dev->idx_out++] = CH341_CMD_I2C_STREAM;
+
+ /* account for stream start and end */
+ avail = SEG_SIZE - 3;
+
+ if (!start_done) {
+ /* Each message has a start */
+ out[dev->idx_out++] = CH341_CMD_I2C_STM_STA;
+
+ avail -= 2; /* room for STA and device address */
+ }
+
+ to_write = min_t(int, len, avail);
+
+ if (!start_done) {
+ out[dev->idx_out++] = CH341_CMD_I2C_STM_OUT | (to_write + 1);
+ out[dev->idx_out++] = msg->addr << 1;
+
+ start_done = true;
+ } else {
+ out[dev->idx_out++] = CH341_CMD_I2C_STM_OUT | to_write;
+ }
+
+ memcpy(&out[dev->idx_out], p, to_write);
+ dev->idx_out += to_write;
+ len -= to_write;
+ p += to_write;
+ }
+
+ return 0;
+}
+
+/*
+ * Append a read command to the request. It usually follows a write
+ * command. When that happens, the driver will attempt to concat the
+ * read command into the same packet. Each read command, of up to 32
+ * bytes, must be written to a new packet. It is not possible to
+ * concat them.
+ */
+static int append_read(struct ch341_i2c *dev, const struct i2c_msg *msg)
+{
+ bool start_done = false;
+ u8 *out = dev->i2c_buf;
+ int len;
+
+ len = msg->len;
+
+ while (len) {
+ int to_read;
+
+ if (dev->idx_out % SEG_SIZE) {
+ if (!start_done &&
+ (dev->idx_out % SEG_SIZE) < (SEG_SIZE - 7)) {
+ /* There's enough left for a read */
+ } else {
+ /* Finish current packet, and advance to the next one */
+ out[dev->idx_out++] = CH341_CMD_I2C_STM_END;
+ dev->out_seg++;
+ dev->idx_out = dev->out_seg * SEG_SIZE;
+
+ if (dev->out_seg == SEG_COUNT)
+ return -E2BIG;
+
+ out[dev->idx_out++] = CH341_CMD_I2C_STREAM;
+ }
+ } else {
+ out[dev->idx_out++] = CH341_CMD_I2C_STREAM;
+ }
+
+ if (!start_done) {
+ /* Each message has a start */
+ out[dev->idx_out++] = CH341_CMD_I2C_STM_STA;
+ out[dev->idx_out++] = CH341_CMD_I2C_STM_OUT | 1;
+ out[dev->idx_out++] = msg->addr << 1 | 1;
+
+ start_done = true;
+ }
+
+ /* Apparently the last command must be an STM_IN to
+ * read the last byte. Without it, the adapter gets
+ * lost.
+ */
+ to_read = min_t(int, len, 32);
+ len -= to_read;
+ if (len == 0) {
+ if (to_read > 1)
+ out[dev->idx_out++] = CH341_CMD_I2C_STM_IN | (to_read - 1);
+ out[dev->idx_out++] = CH341_CMD_I2C_STM_IN;
+ } else {
+ out[dev->idx_out++] = CH341_CMD_I2C_STM_IN | to_read;
+ }
+ }
+
+ return 0;
+}
+
+static int ch341_i2c_xfer(struct i2c_adapter *adapter, struct i2c_msg *msgs, int num)
+{
+ struct ch341_i2c *dev = i2c_get_adapdata(adapter);
+ struct ch341_ddata *ddata = adapter->algo_data;
+ u8 *out = dev->i2c_buf;
+ int actual;
+ int ret;
+ int i;
+
+ /* Special case */
+ if (num == 1 && msgs[0].len == 0)
+ return no_data_xfer(adapter, &msgs[0]);
+
+ /* Prepare the request */
+ dev->idx_out = 0;
+ dev->out_seg = 0;
+
+ for (i = 0; i != num; i++) {
+ if (msgs[i].flags & I2C_M_RD)
+ ret = append_read(dev, &msgs[i]);
+ else
+ ret = append_write(dev, &msgs[i]);
+
+ if (ret)
+ return ret;
+ }
+
+ /* Finish the last packet */
+ if (SEG_SIZE - (dev->idx_out % SEG_SIZE) < 2) {
+ out[dev->idx_out++] = CH341_CMD_I2C_STM_END;
+
+ dev->out_seg++;
+ if (dev->out_seg == SEG_COUNT)
+ return -E2BIG;
+
+ dev->idx_out = dev->out_seg * SEG_SIZE;
+
+ out[dev->idx_out++] = CH341_CMD_I2C_STREAM;
+ }
+
+ out[dev->idx_out++] = CH341_CMD_I2C_STM_STO;
+ out[dev->idx_out++] = CH341_CMD_I2C_STM_END;
+
+ mutex_lock(&ddata->usb_lock);
+
+ /* Issue the request */
+ ret = usb_bulk_msg(ddata->usb_dev,
+ usb_sndbulkpipe(ddata->usb_dev, ddata->ep_out),
+ dev->i2c_buf, dev->idx_out, &actual, DEFAULT_TIMEOUT_MS);
+ if (ret < 0) {
+ mutex_unlock(&ddata->usb_lock);
+ return ret;
+ }
+
+ for (i = 0; i != num; i++) {
+ if (!(msgs[i].flags & I2C_M_RD))
+ continue;
+
+ ret = usb_bulk_msg(ddata->usb_dev,
+ usb_rcvbulkpipe(ddata->usb_dev, ddata->ep_in),
+ dev->i2c_buf, msgs[i].len, &actual,
+ DEFAULT_TIMEOUT_MS);
+
+ if (ret) {
+ mutex_unlock(&ddata->usb_lock);
+ return ret;
+ }
+
+ if (actual != msgs[i].len) {
+ mutex_unlock(&ddata->usb_lock);
+ return -EIO;
+ }
+
+ memcpy(msgs[i].buf, dev->i2c_buf, actual);
+ }
+
+ mutex_unlock(&ddata->usb_lock);
+
+ return num;
+}
+
+static u32 ch341_i2c_func(struct i2c_adapter *adap)
+{
+ return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
+}
+
+static const struct i2c_algorithm ch341_i2c_algorithm = {
+ .master_xfer = ch341_i2c_xfer,
+ .functionality = ch341_i2c_func,
+};
+
+static const struct i2c_adapter_quirks ch341_i2c_quirks = {
+ .max_read_len = MAX_RW_LENGTH,
+ .max_write_len = MAX_RW_LENGTH,
+};
+
+static int ch341_i2c_probe(struct platform_device *pdev)
+{
+ struct ch341_ddata *ddata = dev_get_drvdata(pdev->dev.parent);
+ struct ch341_i2c *ch341_i2c;
+ int actual;
+ int ret;
+
+ ch341_i2c = devm_kzalloc(&pdev->dev, sizeof(*ch341_i2c), GFP_KERNEL);
+ if (ch341_i2c == NULL)
+ return -ENOMEM;
+
+ ch341_i2c->adapter.owner = THIS_MODULE;
+ ch341_i2c->adapter.class = I2C_CLASS_HWMON;
+ ch341_i2c->adapter.algo = &ch341_i2c_algorithm;
+ ch341_i2c->adapter.algo_data = ddata;
+ ch341_i2c->adapter.quirks = &ch341_i2c_quirks;
+ ch341_i2c->adapter.dev.parent = &pdev->dev;
+ snprintf(ch341_i2c->adapter.name, sizeof(ch341_i2c->adapter.name),
+ "CH341 I2C USB bus %03d device %03d",
+ ddata->usb_dev->bus->busnum, ddata->usb_dev->devnum);
+
+ i2c_set_adapdata(&ch341_i2c->adapter, ch341_i2c);
+ platform_set_drvdata(pdev, ch341_i2c);
+
+ /* Set ch341 i2c speed */
+ ch341_i2c->i2c_buf[0] = CH341_CMD_I2C_STREAM;
+ ch341_i2c->i2c_buf[1] = CH341_CMD_I2C_STM_SET | CH341_I2C_100KHZ;
+ ch341_i2c->i2c_buf[2] = CH341_CMD_I2C_STM_END;
+ mutex_lock(&ddata->usb_lock);
+ ret = usb_bulk_msg(ddata->usb_dev,
+ usb_sndbulkpipe(ddata->usb_dev, ddata->ep_out),
+ ch341_i2c->i2c_buf, 3, &actual, DEFAULT_TIMEOUT_MS);
+ mutex_unlock(&ddata->usb_lock);
+
+ if (ret < 0)
+ return dev_err_probe(&pdev->dev, ret, "Cannot set I2C speed\n");
+
+ return devm_i2c_add_adapter(&pdev->dev, &ch341_i2c->adapter);
+}
+
+static struct platform_driver ch341_i2c_driver = {
+ .driver.name = "ch341-i2c",
+ .probe = ch341_i2c_probe,
+};
+module_platform_driver(ch341_i2c_driver);
+
+MODULE_AUTHOR("Frank Zago <frank@zago.net>");
+MODULE_DESCRIPTION("CH341 USB to I2C");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("platform:ch341-i2c");
The I2C interface can run at 4 different speeds. This driver currently only offer 100kHz. Tested with a variety of I2C sensors, and the IIO subsystem. Signed-off-by: frank zago <frank@zago.net> --- MAINTAINERS | 1 + drivers/i2c/busses/Kconfig | 10 + drivers/i2c/busses/Makefile | 1 + drivers/i2c/busses/i2c-ch341.c | 377 +++++++++++++++++++++++++++++++++ 4 files changed, 389 insertions(+) create mode 100644 drivers/i2c/busses/i2c-ch341.c