From nobody Mon Sep 8 08:51:29 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 C40DDC54EE9 for ; Tue, 13 Sep 2022 15:01:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232941AbiIMPBE (ORCPT ); Tue, 13 Sep 2022 11:01:04 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38016 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235117AbiIMO7P (ORCPT ); Tue, 13 Sep 2022 10:59:15 -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 9F4D37435F; Tue, 13 Sep 2022 07:28:54 -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 ADCACB80F10; Tue, 13 Sep 2022 14:27:40 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1844FC433D6; Tue, 13 Sep 2022 14:27:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1663079259; bh=BfJiQhLhwrKqxBQes+zZPYx3vVbxiZ69uhmlnacsYLw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=y5oeKTjWx2PezWI+BR338LIH4cne+Ng3PdwMlwyVqJFq3Tfqxu+Re67on+U5cLrP5 DSuYBPqAVl8i54FbnOydUSts40tfvjtT+wZD0JtKOu4Bg1IoqpAFfyrGeuEb1XfBwF r1R1W9B2Dx6lRZUlNdNO1zPMAwbheB8Np2WKEgK8= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Jonathan Woithe , Johan Hovold Subject: [PATCH 5.4 065/108] USB: serial: ch341: fix lost character on LCR updates Date: Tue, 13 Sep 2022 16:06:36 +0200 Message-Id: <20220913140356.414321363@linuxfoundation.org> X-Mailer: git-send-email 2.37.3 In-Reply-To: <20220913140353.549108748@linuxfoundation.org> References: <20220913140353.549108748@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 5.4 ] 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 @@ -96,7 +96,9 @@ struct ch341_private { u8 mcr; u8 msr; u8 lcr; + unsigned long quirks; + u8 version; }; =20 static void ch341_set_termios(struct tty_struct *tty, @@ -182,6 +184,9 @@ 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; @@ -233,7 +238,9 @@ 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)