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USB: serial: ch341: fix disabled rx timer on older devices

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commit 41ca302a69 upstream.

At least one older CH341 appears to have the RX timer enable bit
inverted so that setting it disables the RX timer and prevents the FIFO
from emptying until it is full.

Only set the RX timer enable bit for devices with version newer than
0x27 (even though this probably affects all pre-0x30 devices).

Reported-by: Jonathan Woithe <jwoithe@just42.net>
Tested-by: Jonathan Woithe <jwoithe@just42.net>
Link: https://lore.kernel.org/r/Ys1iPTfiZRWj2gXs@marvin.atrad.com.au
Fixes: 4e46c410e0 ("USB: serial: ch341: reinitialize chip on reconfiguration")
Cc: stable@vger.kernel.org      # 4.10
Signed-off-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Johan Hovold 2022-09-06 14:21:27 +02:00 committed by Greg Kroah-Hartman
parent e0923b4f38
commit e1779c25e4
1 changed files with 5 additions and 1 deletions
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6
drivers/usb/serial/ch341.c
View file

@ -259,8 +259,12 @@ static int ch341_set_baudrate_lcr(struct usb_device *dev,
/*
* CH341A buffers data until a full endpoint-size packet (32 bytes)
* has been received unless bit 7 is set.
*
* At least one device with version 0x27 appears to have this bit
* inverted.
*/
val |= BIT(7);
if (priv->version > 0x27)
val |= BIT(7);
r = ch341_control_out(dev, CH341_REQ_WRITE_REG,
CH341_REG_DIVISOR << 8 | CH341_REG_PRESCALER,