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Commit 3a8d1ca7 authored by Brant Merryman's avatar Brant Merryman Committed by Greg Kroah-Hartman
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USB: serial: cp210x: re-enable auto-RTS on open 



commit c7614ff9b73a1e6fb2b1b51396da132ed22fecdb upstream.

CP210x hardware disables auto-RTS but leaves auto-CTS when in hardware
flow control mode and UART on cp210x hardware is disabled. When
re-opening the port, if auto-CTS is enabled on the cp210x, then auto-RTS
must be re-enabled in the driver.

Signed-off-by: default avatarBrant Merryman <brant.merryman@silabs.com>
Co-developed-by: default avatarPhu Luu <phu.luu@silabs.com>
Signed-off-by: default avatarPhu Luu <phu.luu@silabs.com>
Link: https://lore.kernel.org/r/ECCF8E73-91F3-4080-BE17-1714BC8818FB@silabs.com


[ johan: fix up tags and problem description ]
Fixes: 39a66b8d ("[PATCH] USB: CP2101 Add support for flow control")
Cc: stable <stable@vger.kernel.org>     # 2.6.12
Signed-off-by: default avatarJohan Hovold <johan@kernel.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 378737e1

drivers/usb/serial/cp210x.c

+17 −0
Original line number Diff line number Diff line
@@ -915,6 +915,7 @@ static void cp210x_get_termios_port(struct usb_serial_port *port, 
	u32 baud;

	u16 bits;

	u32 ctl_hs;

	u32 flow_repl;



	cp210x_read_u32_reg(port, CP210X_GET_BAUDRATE, &baud);
@@ -1015,6 +1016,22 @@ static void cp210x_get_termios_port(struct usb_serial_port *port, 
	ctl_hs = le32_to_cpu(flow_ctl.ulControlHandshake);

	if (ctl_hs & CP210X_SERIAL_CTS_HANDSHAKE) {

		dev_dbg(dev, "%s - flow control = CRTSCTS\n", __func__);

		/*

		 * When the port is closed, the CP210x hardware disables

		 * auto-RTS and RTS is deasserted but it leaves auto-CTS when

		 * in hardware flow control mode. When re-opening the port, if

		 * auto-CTS is enabled on the cp210x, then auto-RTS must be

		 * re-enabled in the driver.

		 */

		flow_repl = le32_to_cpu(flow_ctl.ulFlowReplace);

		flow_repl &= ~CP210X_SERIAL_RTS_MASK;

		flow_repl |= CP210X_SERIAL_RTS_SHIFT(CP210X_SERIAL_RTS_FLOW_CTL);

		flow_ctl.ulFlowReplace = cpu_to_le32(flow_repl);

		cp210x_write_reg_block(port,

				CP210X_SET_FLOW,

				&flow_ctl,

				sizeof(flow_ctl));



		cflag |= CRTSCTS;

	} else {

		dev_dbg(dev, "%s - flow control = NONE\n", __func__);