From nobody Thu Sep 4 03:28:47 2025 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2C296C54EE9 for ; Tue, 13 Sep 2022 17:06:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232384AbiIMRG1 (ORCPT ); Tue, 13 Sep 2022 13:06:27 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36568 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232367AbiIMRGB (ORCPT ); Tue, 13 Sep 2022 13:06:01 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2ECA383F37; Tue, 13 Sep 2022 08:55:31 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id D4FE5B80F93; Tue, 13 Sep 2022 14:33:00 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 48C47C433B5; Tue, 13 Sep 2022 14:32:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1663079579; bh=HwcKgcx3YUW4O5fZ2Dy56K8an7bFPB5SAM8Cc7hYdjM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=JycDiVG3WxZgYxXeB8FI3lh/mBbcrIkej/L1cQ9DOVYTHw4lgT9xRyZp+rRWZpkit cU9f3Wk8215O6D1+EC9gCACSzuJMeogxTi3lBm6yrUp5U94Zk9tCvo3jgwdrMFnV8w tgpm4TvyLu14tg2skmk7Vz0D5tPr1Me3a/60kDLM= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Jonathan Woithe , Johan Hovold Subject: [PATCH 4.19 74/79] USB: serial: ch341: fix lost character on LCR updates Date: Tue, 13 Sep 2022 16:07:32 +0200 Message-Id: <20220913140352.462146395@linuxfoundation.org> X-Mailer: git-send-email 2.37.3 In-Reply-To: <20220913140348.835121645@linuxfoundation.org> References: <20220913140348.835121645@linuxfoundation.org> User-Agent: quilt/0.67 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" From: 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 Tested-by: Jonathan Woithe Link: https://lore.kernel.org/r/Ys1iPTfiZRWj2gXs@marvin.atrad.com.au Fixes: 4e46c410e050 ("USB: serial: ch341: reinitialize chip on reconfigurat= ion") Fixes: 55fa15b5987d ("USB: serial: ch341: fix baud rate and line-control ha= ndling") Cc: stable@vger.kernel.org # 4.10 Signed-off-by: Johan Hovold [ johan: adjust context to 4.19 ] Signed-off-by: Johan Hovold Signed-off-by: Greg Kroah-Hartman --- drivers/usb/serial/ch341.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) --- a/drivers/usb/serial/ch341.c +++ b/drivers/usb/serial/ch341.c @@ -96,6 +96,8 @@ struct ch341_private { u8 mcr; u8 msr; u8 lcr; + + u8 version; }; =20 static void ch341_set_termios(struct tty_struct *tty, @@ -181,6 +183,9 @@ static int ch341_set_baudrate_lcr(struct if (r) return r; =20 + if (priv->version < 0x30) + return 0; + r =3D ch341_control_out(dev, CH341_REQ_WRITE_REG, 0x2518, lcr); if (r) return r; @@ -232,7 +237,9 @@ static int ch341_configure(struct usb_de r =3D 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 =3D buffer[0]; + dev_dbg(&dev->dev, "Chip version: 0x%02x\n", priv->version); =20 r =3D ch341_control_out(dev, CH341_REQ_SERIAL_INIT, 0, 0); if (r < 0)