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USB: serial: cp210x: re-enable auto-RTS on open

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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: Brant Merryman <brant.merryman@silabs.com>
Co-developed-by: Phu Luu <phu.luu@silabs.com>
Signed-off-by: Phu 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: 39a66b8d22 ("[PATCH] USB: CP2101 Add support for flow control")
Cc: stable <stable@vger.kernel.org>     # 2.6.12
Signed-off-by: Johan Hovold <johan@kernel.org>
This commit is contained in:
Brant Merryman 2020-06-26 04:24:20 +00:00 committed by Johan Hovold
parent 4387b3dbb0
commit c7614ff9b7
1 changed files with 17 additions and 0 deletions
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17
drivers/usb/serial/cp210x.c
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@ -917,6 +917,7 @@ 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);
@ -1017,6 +1018,22 @@ 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__);