From nobody Tue Apr 7 05:21:13 2026 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 B2118C3DA6B for ; Wed, 31 Aug 2022 08:15:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230226AbiHaIPq (ORCPT ); Wed, 31 Aug 2022 04:15:46 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60186 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231292AbiHaIPi (ORCPT ); Wed, 31 Aug 2022 04:15:38 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id F3A9B67177; Wed, 31 Aug 2022 01:15:36 -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 dfw.source.kernel.org (Postfix) with ESMTPS id 860606198E; Wed, 31 Aug 2022 08:15:36 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id DED04C433C1; Wed, 31 Aug 2022 08:15:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1661933735; bh=+7v+mKDgW+IHX/GhERatR6jBtG0aN65CVgOFZj60fjc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=UiA32G8nKw2SXdNn1AShGphfXahL8TREP5HGgwmK28xdzoy8/C2hzzQKfclaG0SJl NwqNzqDtlJxcKhvWq5bK3RiiUnzr1RdWmXTK3b3dZE6jLc7zkptDs6YofhHac/twxz CGY0frtsQRDdoafslByShDYajCXpnBR5qw/yWU+qQjSnZ/RG/lFLq0TVb/VwYQbn90 3H/MtXKUwL/N436BpvwfZVxd/FLVTQVw/OdkrAepv/6nIX+ZrvPErQ+MXNg8Gmi8Uf AVMdd9yYqBOI19xCf9S5soT8fkvOZhFc8E07U26j7iKJMa+J7m5TyAStcKQu99z8Ci Q/wbedYc6YYEg== Received: from johan by xi.lan with local (Exim 4.94.2) (envelope-from ) id 1oTIsn-0007xA-NM; Wed, 31 Aug 2022 10:15:33 +0200 From: Johan Hovold To: Johan Hovold , Jonathan Woithe Cc: linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: [PATCH 1/2] USB: serial: ch341: fix lost character on LCR updates Date: Wed, 31 Aug 2022 10:15:24 +0200 Message-Id: <20220831081525.30557-2-johan@kernel.org> X-Mailer: git-send-email 2.35.1 In-Reply-To: <20220831081525.30557-1-johan@kernel.org> References: <20220831081525.30557-1-johan@kernel.org> 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" 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 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 --- 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 2798fca71261..2bcce172355b 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; }; =20 @@ -265,6 +268,9 @@ static int ch341_set_baudrate_lcr(struct usb_device *de= v, * (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 =3D ch341_control_out(dev, CH341_REQ_WRITE_REG, CH341_REG_LCR2 << 8 | CH341_REG_LCR, lcr); if (r) @@ -308,7 +314,9 @@ static int ch341_configure(struct usb_device *dev, stru= ct ch341_private *priv) r =3D ch341_control_in(dev, CH341_REQ_READ_VERSION, 0, 0, buffer, size); if (r) return r; - 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) --=20 2.35.1