spi: add ch341a usb2spi driver

diff --git a/drivers/spi/Kconfig b/drivers/spi/Kconfig
index a2c99ff33e0a..79b3c20d7537 100644
--- a/drivers/spi/Kconfig
+++ b/drivers/spi/Kconfig
@@ -1198,6 +1198,12 @@  config SPI_AMD
 	help
 	  Enables SPI controller driver for AMD SoC.
 
+config SPI_CH341
+	tristate "CH341 USB2SPI adapter"
+	depends on SPI_MASTER && USB
+	help
+	  Enables the SPI controller on the CH341a USB to serial chip
+
 #
 # Add new SPI master controllers in alphabetical order above this line
 #
diff --git a/drivers/spi/Makefile b/drivers/spi/Makefile
index e694254dec04..9de506d1d135 100644
--- a/drivers/spi/Makefile
+++ b/drivers/spi/Makefile
@@ -154,6 +154,7 @@  obj-$(CONFIG_SPI_XTENSA_XTFPGA)		+= spi-xtensa-xtfpga.o
 obj-$(CONFIG_SPI_ZYNQ_QSPI)		+= spi-zynq-qspi.o
 obj-$(CONFIG_SPI_ZYNQMP_GQSPI)		+= spi-zynqmp-gqspi.o
 obj-$(CONFIG_SPI_AMD)			+= spi-amd.o
+obj-$(CONFIG_SPI_CH341)			+= spi-ch341.o
 
 # SPI slave protocol handlers
 obj-$(CONFIG_SPI_SLAVE_TIME)		+= spi-slave-time.o
diff --git a/drivers/spi/spi-ch341.c b/drivers/spi/spi-ch341.c
new file mode 100644
index 000000000000..a2b53089e0e4
--- /dev/null
+++ b/drivers/spi/spi-ch341.c
@@ -0,0 +1,236 @@ 
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * QiHeng Electronics ch341a USB-to-SPI adapter driver
+ *
+ * Copyright (C) 2024 Johannes Thumshirn <jth@kernel.org>
+ *
+ * Based on ch341a_spi.c from the flashrom project.
+ */
+#include <linux/module.h>
+#include <linux/usb.h>
+#include <linux/spi/spi.h>
+
+#define CH341_PACKET_LENGTH 32
+#define CH341_DEFAULT_TIMEOUT 1000
+
+#define CH341A_CMD_UIO_STREAM 0xab
+
+#define CH341A_CMD_UIO_STM_END 0x20
+#define CH341A_CMD_UIO_STM_DIR 0x40
+#define CH341A_CMD_UIO_STM_OUT 0x80
+
+#define CH341A_CMD_I2C_STREAM 0xaa
+#define CH341A_CMD_I2C_STM_SET 0x60
+#define CH341A_CMD_I2C_STM_END 0x00
+
+#define CH341A_CMD_SPI_STREAM 0xa8
+
+#define CH341A_STM_I2C_100K 0x01
+
+struct ch341_spi_dev {
+	struct spi_controller *ctrl;
+	struct usb_device *udev;
+	unsigned int write_pipe;
+	unsigned int read_pipe;
+	int rx_len;
+	void *rx_buf;
+	u8 *tx_buf;
+	struct urb *rx_urb;
+	struct spi_device *spidev;
+};
+
+static void ch341_set_cs(struct spi_device *spi, bool is_high)
+{
+	struct ch341_spi_dev *ch341 =
+		spi_controller_get_devdata(spi->controller);
+
+	memset(ch341->tx_buf, 0, CH341_PACKET_LENGTH);
+	ch341->tx_buf[0] = CH341A_CMD_UIO_STREAM;
+	ch341->tx_buf[1] = CH341A_CMD_UIO_STM_OUT | (is_high ? 0x36 : 0x37);
+
+	if (is_high) {
+		ch341->tx_buf[2] = CH341A_CMD_UIO_STM_DIR | 0x3f;
+		ch341->tx_buf[3] = CH341A_CMD_UIO_STM_END;
+	} else {
+		ch341->tx_buf[2] = CH341A_CMD_UIO_STM_END;
+	}
+
+	(void)usb_bulk_msg(ch341->udev, ch341->write_pipe, ch341->tx_buf,
+			   (is_high ? 4 : 3), NULL, CH341_DEFAULT_TIMEOUT);
+}
+
+static int ch341_transfer_one(struct spi_controller *host,
+			      struct spi_device *spi,
+			      struct spi_transfer *trans)
+{
+	struct ch341_spi_dev *ch341 =
+		spi_controller_get_devdata(spi->controller);
+	int len;
+	int ret;
+
+	len = min(CH341_PACKET_LENGTH, trans->len + 1);
+
+	memset(ch341->tx_buf, 0, CH341_PACKET_LENGTH);
+
+	ch341->tx_buf[0] = CH341A_CMD_SPI_STREAM;
+
+	memcpy(ch341->tx_buf + 1, trans->tx_buf, len);
+
+	ret = usb_bulk_msg(ch341->udev, ch341->write_pipe, ch341->tx_buf, len,
+			   NULL, CH341_DEFAULT_TIMEOUT);
+	if (ret)
+		return ret;
+
+	return usb_bulk_msg(ch341->udev, ch341->read_pipe, trans->rx_buf,
+			    len - 1, NULL, CH341_DEFAULT_TIMEOUT);
+}
+
+static void ch341_recv(struct urb *urb)
+{
+	struct ch341_spi_dev *ch341 = urb->context;
+	struct usb_device *udev = ch341->udev;
+
+	switch (urb->status) {
+	case 0:
+		/* success */
+		break;
+	case -ENOENT:
+	case -ECONNRESET:
+	case -EPIPE:
+	case -ESHUTDOWN:
+		dev_dbg(&udev->dev, "rx urb terminated with status: %d\n",
+			urb->status);
+		return;
+	default:
+		dev_dbg(&udev->dev, "rx urb error: %d\n", urb->status);
+		break;
+	}
+}
+
+static int ch341_config_stream(struct ch341_spi_dev *ch341, int speed)
+{
+	memset(ch341->tx_buf, 0, CH341_PACKET_LENGTH);
+	ch341->tx_buf[0] = CH341A_CMD_I2C_STREAM;
+	ch341->tx_buf[1] = CH341A_CMD_I2C_STM_SET | (speed & 0x7);
+	ch341->tx_buf[2] = CH341A_CMD_I2C_STM_END;
+
+	return usb_bulk_msg(ch341->udev, ch341->write_pipe, ch341->tx_buf, 3,
+			    NULL, CH341_DEFAULT_TIMEOUT);
+}
+
+static int ch341_enable_pins(struct ch341_spi_dev *ch341, bool enable)
+{
+	memset(ch341->tx_buf, 0, CH341_PACKET_LENGTH);
+	ch341->tx_buf[0] = CH341A_CMD_UIO_STREAM;
+	ch341->tx_buf[1] = CH341A_CMD_UIO_STM_OUT | 0x37;
+	ch341->tx_buf[2] = CH341A_CMD_UIO_STM_DIR | (enable ? 0x3f : 0x00);
+	ch341->tx_buf[3] = CH341A_CMD_UIO_STM_END;
+
+	return usb_bulk_msg(ch341->udev, ch341->write_pipe, ch341->tx_buf, 4,
+			    NULL, CH341_DEFAULT_TIMEOUT);
+}
+
+static struct spi_board_info chip = {
+	.modalias = "spi-ch341a",
+};
+
+static int ch341_probe(struct usb_interface *intf,
+		       const struct usb_device_id *id)
+{
+	struct usb_device *udev = interface_to_usbdev(intf);
+	struct usb_endpoint_descriptor *in, *out;
+	struct ch341_spi_dev *ch341;
+	struct spi_controller *ctrl;
+	int ret;
+
+	ret = usb_find_common_endpoints(intf->cur_altsetting, &in, &out, NULL,
+					NULL);
+	if (ret)
+		return ret;
+
+	ctrl = devm_spi_alloc_master(&udev->dev, sizeof(struct ch341_spi_dev));
+	if (!ctrl)
+		return -ENOMEM;
+
+	ch341 = spi_controller_get_devdata(ctrl);
+	ch341->ctrl = ctrl;
+	ch341->udev = udev;
+	ch341->write_pipe = usb_sndbulkpipe(udev, usb_endpoint_num(out));
+	ch341->read_pipe = usb_rcvbulkpipe(udev, usb_endpoint_num(in));
+
+	ch341->rx_len = usb_endpoint_maxp(in);
+	ch341->rx_buf = devm_kzalloc(&udev->dev, ch341->rx_len, GFP_KERNEL);
+	if (!ch341->rx_buf)
+		return -ENOMEM;
+
+	ch341->rx_urb = usb_alloc_urb(0, GFP_KERNEL);
+	if (!ch341->rx_urb)
+		return -ENOMEM;
+
+	ch341->tx_buf =
+		devm_kzalloc(&udev->dev, CH341_PACKET_LENGTH, GFP_KERNEL);
+	if (!ch341->tx_buf)
+		return -ENOMEM;
+
+	usb_fill_bulk_urb(ch341->rx_urb, udev, ch341->read_pipe, ch341->rx_buf,
+			  ch341->rx_len, ch341_recv, ch341);
+
+	ret = usb_submit_urb(ch341->rx_urb, GFP_KERNEL);
+	if (ret) {
+		usb_free_urb(ch341->rx_urb);
+		return -ENOMEM;
+	}
+
+	ctrl->bus_num = -1;
+	ctrl->mode_bits = SPI_CPHA;
+	ctrl->transfer_one = ch341_transfer_one;
+	ctrl->set_cs = ch341_set_cs;
+	ctrl->auto_runtime_pm = false;
+
+	usb_set_intfdata(intf, ch341);
+
+	ret = ch341_config_stream(ch341, CH341A_STM_I2C_100K);
+	if (ret)
+		return ret;
+
+	ret = ch341_enable_pins(ch341, true);
+	if (ret)
+		return ret;
+
+	ret = spi_register_controller(ctrl);
+	if (ret)
+		return ret;
+
+	ch341->spidev = spi_new_device(ctrl, &chip);
+	if (!ch341->spidev)
+		return -ENOMEM;
+
+	return 0;
+}
+
+static void ch341_disconnect(struct usb_interface *intf)
+{
+	struct ch341_spi_dev *ch341 = usb_get_intfdata(intf);
+
+	spi_unregister_controller(ch341->ctrl);
+	ch341_enable_pins(ch341, false);
+	usb_free_urb(ch341->rx_urb);
+}
+
+static const struct usb_device_id ch341_id_table[] = {
+	{ USB_DEVICE(0x1a86, 0x5512) },
+	{ }
+};
+MODULE_DEVICE_TABLE(usb, ch341_id_table);
+
+static struct usb_driver ch341a_usb_driver = {
+	.name = "spi-ch341",
+	.probe = ch341_probe,
+	.disconnect = ch341_disconnect,
+	.id_table = ch341_id_table,
+};
+module_usb_driver(ch341a_usb_driver);
+
+MODULE_AUTHOR("Johannes Thumshirn <jth@kernel.org>");
+MODULE_DESCRIPTION("QiHeng Electronics ch341 USB2SPI");
+MODULE_LICENSE("GPL v2");