[PATCH stable-5.15 0/2] USB: serial: ch341: backports to 5.15

[PATCH stable-5.15 0/2] USB: serial: ch341: backports to 5.15

[Johan Hovold]

Here are backports of two patches that failed to apply to 5.15 and older
stable trees.

Only the first one actually needed to have some context adjusted.

Johan


Johan Hovold (2):
  USB: serial: ch341: fix lost character on LCR updates
  USB: serial: ch341: fix disabled rx timer on older devices

 drivers/usb/serial/ch341.c | 16 ++++++++++++++--
 1 file changed, 14 insertions(+), 2 deletions(-)

-- 
2.35.1

[PATCH stable-5.15 1/2] USB: serial: ch341: fix lost character on LCR updates

[Johan Hovold]

commit 8e83622ae7ca481c76c8fd9579877f6abae64ca2 upstream.

Disable LCR updates for pre-0x30 devices which use a different (unknown)
protocol for line control and where the current register write causes
the next received character to be lost.

Note that updating LCR using the INIT command has no effect on these
devices either.

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: 4e46c410e050 ("USB: serial: ch341: reinitialize chip on reconfiguration")
Fixes: 55fa15b5987d ("USB: serial: ch341: fix baud rate and line-control handling")
Cc: stable@vger.kernel.org      # 4.10
Signed-off-by: Johan Hovold <johan@kernel.org>
[ johan: adjust context to 5.15 ]
Signed-off-by: Johan Hovold <johan@kernel.org>
---
 drivers/usb/serial/ch341.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/serial/ch341.c b/drivers/usb/serial/ch341.c
index b5a1864e9cfd..b787533aec64 100644
--- a/drivers/usb/serial/ch341.c
+++ b/drivers/usb/serial/ch341.c
@@ -97,7 +97,10 @@ struct ch341_private {
 	u8 mcr;
 	u8 msr;
 	u8 lcr;
+
 	unsigned long quirks;
+	u8 version;
+
 	unsigned long break_end;
 };
 
@@ -271,6 +274,9 @@ static int ch341_set_baudrate_lcr(struct usb_device *dev,
 	 * (stop bits, parity and word length). Version 0x30 and above use
 	 * CH341_REG_LCR only and CH341_REG_LCR2 is always set to zero.
 	 */
+	if (priv->version < 0x30)
+		return 0;
+
 	r = ch341_control_out(dev, CH341_REQ_WRITE_REG,
 			      CH341_REG_LCR2 << 8 | CH341_REG_LCR, lcr);
 	if (r)
@@ -323,7 +329,9 @@ static int ch341_configure(struct usb_device *dev, struct ch341_private *priv)
 	r = ch341_control_in(dev, CH341_REQ_READ_VERSION, 0, 0, buffer, size);
 	if (r < 0)
 		goto out;
-	dev_dbg(&dev->dev, "Chip version: 0x%02x\n", buffer[0]);
+
+	priv->version = buffer[0];
+	dev_dbg(&dev->dev, "Chip version: 0x%02x\n", priv->version);
 
 	r = ch341_control_out(dev, CH341_REQ_SERIAL_INIT, 0, 0);
 	if (r < 0)
-- 
2.35.1

[PATCH stable-5.15 2/2] USB: serial: ch341: fix disabled rx timer on older devices

[Johan Hovold]

commit 41ca302a697b64a3dab4676e01d0d11bb184737d 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: 4e46c410e050 ("USB: serial: ch341: reinitialize chip on reconfiguration")
Cc: stable@vger.kernel.org      # 4.10
Signed-off-by: Johan Hovold <johan@kernel.org>
---
 drivers/usb/serial/ch341.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/serial/ch341.c b/drivers/usb/serial/ch341.c
index b787533aec64..752daa952abd 100644
--- a/drivers/usb/serial/ch341.c
+++ b/drivers/usb/serial/ch341.c
@@ -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,
-- 
2.35.1

Re: [PATCH stable-5.15 0/2] USB: serial: ch341: backports to 5.15

[Greg Kroah-Hartman]

On Tue, Sep 06, 2022 at 02:21:25PM +0200, Johan Hovold wrote:
> Here are backports of two patches that failed to apply to 5.15 and older
> stable trees.
> 
> Only the first one actually needed to have some context adjusted.

Applied to 5.10.y and 5.15.y.  didn't apply to anything older, odds are
no one cares about this driver for those kernels anyway :)

thanks,

greg k-h

Re: [PATCH stable-5.15 0/2] USB: serial: ch341: backports to 5.15

[Johan Hovold]

On Tue, Sep 06, 2022 at 03:19:38PM +0200, Greg Kroah-Hartman wrote:
> On Tue, Sep 06, 2022 at 02:21:25PM +0200, Johan Hovold wrote:
> > Here are backports of two patches that failed to apply to 5.15 and older
> > stable trees.
> > 
> > Only the first one actually needed to have some context adjusted.
> 
> Applied to 5.10.y and 5.15.y.  didn't apply to anything older, odds are
> no one cares about this driver for those kernels anyway :)

True. But now backported for "completeness". :)

Johan