This is a note to let you know that I've just added the patch titled
USB: serial: cp210x: re-enable auto-RTS on open
to my usb git tree which can be found at
git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git
in the usb-testing branch.
The patch will show up in the next release of the linux-next tree
(usually sometime within the next 24 hours during the week.)
The patch will be merged to the usb-next branch sometime soon,
after it passes testing, and the merge window is open.
If you have any questions about this process, please let me know.
>From c7614ff9b73a1e6fb2b1b51396da132ed22fecdb Mon Sep 17 00:00:00 2001
From: Brant Merryman <brant.merryman@xxxxxxxxxx>
Date: Fri, 26 Jun 2020 04:24:20 +0000
Subject: USB: serial: cp210x: re-enable auto-RTS on open
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@xxxxxxxxxx>
Co-developed-by: Phu Luu <phu.luu@xxxxxxxxxx>
Signed-off-by: Phu Luu <phu.luu@xxxxxxxxxx>
Link: https://lore.kernel.org/r/ECCF8E73-91F3-4080-BE17-1714BC8818FB@xxxxxxxxxx
[ johan: fix up tags and problem description ]
Fixes: 39a66b8d22a3 ("[PATCH] USB: CP2101 Add support for flow control")
Cc: stable <stable@xxxxxxxxxxxxxxx> # 2.6.12
Signed-off-by: Johan Hovold <johan@xxxxxxxxxx>
---
drivers/usb/serial/cp210x.c | 17 +++++++++++++++++
1 file changed, 17 insertions(+)
diff --git a/drivers/usb/serial/cp210x.c b/drivers/usb/serial/cp210x.c
index bcceb4ad8be0..a90801ef0055 100644
--- a/drivers/usb/serial/cp210x.c
+++ b/drivers/usb/serial/cp210x.c
@@ -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__);
--
2.27.0
