drivers/usb/gadget.c: Add support for EHCI debug using the WCH CH347

The WCH CH347 presents a USB CDC serial port on interface 4 while in
operating modes 0, 1, and 3. Mode 0 also presents a UART on interface
2 but this is ignored for compatibility with the other modes. Mode 2
uses vendor defined HID usages for communication and is not currently
supported. Like the FT232H the data format is hard coded to 8n1.

Tested using a CH347 breakout board and a Dell Latitude E6400.

Change-Id: Ibd4ad17b7369948003fff7e825b46fe852bc7eb9
Signed-off-by: Nicholas Chin <nic.c3.14@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/68264
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Kyösti Mälkki <kyosti.malkki@gmail.com>

2 files changed, 87 insertions, 0 deletions

diff --git a/src/drivers/usb/Kconfig b/src/drivers/usb/Kconfig
index 6854c4a6b6..36fda75c8d 100644
--- a/src/drivers/usb/Kconfig
+++ b/src/drivers/usb/Kconfig
@@ -92,6 +92,14 @@ config USBDEBUG_DONGLE_FTDI_FT232H
 	  Use this with FT232H usb-to-uart. Configuration is hard-coded
 	  to use 8n1, no flow control.
 
+config USBDEBUG_DONGLE_WCH_CH347
+	bool "WCH CH347 UART"
+	help
+	  Use this with CH347 usb-to-uart. Configuration is hard-coded
+	  to use 8n1, no flow control. For compatibility across modes
+	  0, 1, and 3, only UART 1 is supported. The UART in mode 2 is
+	  not currently supported.
+
 endchoice
 
 config USBDEBUG_DONGLE_FTDI_FT232H_BAUD
@@ -104,6 +112,16 @@ config USBDEBUG_DONGLE_FTDI_FT232H_BAUD
 	  connection works with it. Multiples of 115,200 seem to be a good
 	  choice, and EHCI debug usually can't saturate more than 576,000.
 
+config USBDEBUG_DONGLE_WCH_CH347_BAUD
+	int "WCH CH347 baud rate"
+	default 115200
+	depends on USBDEBUG_DONGLE_WCH_CH347
+	help
+	  Select baud rate for CH347 in the range 1200..9,000,000. Make
+	  sure that your receiving side supports the same setting and your
+	  connection works with it. Multiples of 115,200 seem to be a good
+	  choice, and EHCI debug usually can't saturate more than 576,000.
+
 config USBDEBUG_OPTIONAL_HUB_PORT
 	int
 	default 2 if USBDEBUG_DONGLE_BEAGLEBONE
diff --git a/src/drivers/usb/gadget.c b/src/drivers/usb/gadget.c
index fcb361cc83..d7614474ce 100644
--- a/src/drivers/usb/gadget.c
+++ b/src/drivers/usb/gadget.c
@@ -205,6 +205,73 @@ small_write:
 	return 0;
 }
 
+/* Refer to USB CDC PSTN Subclass specification section 6.3 */
+#define CDC_SET_LINE_CODING_REQUEST 0x20
+struct cdc_line_coding {
+	u32 baudrate;
+	u8 stop_bits;
+	u8 parity;
+	u8 data_bits;
+} __packed;
+
+static int probe_for_ch347(struct ehci_dbg_port *ehci_debug, struct dbgp_pipe *pipe)
+{
+	int ret;
+	u8 devnum = 0;
+	u8 uart_if = 2; /* CH347 UART 1 */
+
+	/* Move the device to 127 if it isn't already there */
+	ret = dbgp_control_msg(ehci_debug, devnum,
+		USB_DIR_OUT | USB_TYPE_STANDARD | USB_RECIP_DEVICE,
+		USB_REQ_SET_ADDRESS, USB_DEBUG_DEVNUM, 0, NULL, 0);
+	if (ret < 0) {
+		printk(BIOS_INFO, "Could not move attached device to %d.\n",
+			USB_DEBUG_DEVNUM);
+			return -2;
+	}
+	devnum = USB_DEBUG_DEVNUM;
+	printk(BIOS_INFO, "EHCI debug device renamed to %d.\n", devnum);
+
+	/* Send Set Configure request to device.  */
+	ret = dbgp_control_msg(ehci_debug, devnum,
+		USB_DIR_OUT | USB_TYPE_STANDARD | USB_RECIP_DEVICE,
+		USB_REQ_SET_CONFIGURATION, 1, 0, NULL, 0);
+	if (ret < 0) {
+		printk(BIOS_INFO, "CH347 set configuration failed.\n");
+		return -2;
+	}
+
+	struct cdc_line_coding line_coding = {
+		.baudrate = CONFIG_USBDEBUG_DONGLE_WCH_CH347_BAUD,
+		.stop_bits = 0, /* 1 stop bit */
+		.parity = 0, /* No parity */
+		.data_bits = 8
+	};
+
+	ret = dbgp_control_msg(ehci_debug, devnum,
+		USB_DIR_OUT | USB_TYPE_CLASS | USB_RECIP_INTERFACE,
+		CDC_SET_LINE_CODING_REQUEST, 0, uart_if, &line_coding, sizeof(line_coding));
+	if (ret < 0) {
+		printk(BIOS_INFO, "CDC SET_LINE_CODING failed.\n");
+		return -3;
+	}
+
+	/* Modes 0, 1, and 3 all have UART 1 on endpoint 4 in common */
+	pipe[DBGP_CONSOLE_EPOUT].endpoint = 0x04;
+	pipe[DBGP_CONSOLE_EPIN].endpoint = 0x84;
+
+	ack_set_configuration(pipe, devnum, 1000);
+
+	/* Perform a small write. */
+	ret = dbgp_bulk_write_x(&pipe[DBGP_CONSOLE_EPOUT], "USB\r\n", 5);
+	if (ret < 0) {
+		printk(BIOS_INFO, "dbgp_bulk_write failed: %d\n", ret);
+		return -4;
+	}
+	printk(BIOS_INFO, "Test write done\n");
+	return 0;
+}
+
 /* FTDI FT232H UART programming. */
 #define FTDI_SIO_SET_FLOW_CTRL_REQUEST 0x02
 #define FTDI_SIO_SET_BAUDRATE_REQUEST  0x03
@@ -329,6 +396,8 @@ int dbgp_probe_gadget(struct ehci_dbg_port *ehci_debug, struct dbgp_pipe *pipe)
 
 	if (CONFIG(USBDEBUG_DONGLE_FTDI_FT232H)) {
 		ret = probe_for_ftdi(ehci_debug, pipe);
+	} else if (CONFIG(USBDEBUG_DONGLE_WCH_CH347)) {
+		ret = probe_for_ch347(ehci_debug, pipe);
 	} else {
 		ret = probe_for_debug_descriptor(ehci_debug, pipe);
 	}