From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-19.4 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id C1413C19F36 for ; Fri, 13 Aug 2021 15:09:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A9BB6610A5 for ; Fri, 13 Aug 2021 15:09:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S241334AbhHMPJc (ORCPT ); Fri, 13 Aug 2021 11:09:32 -0400 Received: from mail.kernel.org ([198.145.29.99]:52118 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S241223AbhHMPJY (ORCPT ); Fri, 13 Aug 2021 11:09:24 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 614466109D; Fri, 13 Aug 2021 15:08:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1628867337; bh=I4m2kPY9UgdBTkTiWJFQgRp5uiCVjYQUXB2EydW5tUA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=k/JBh0Q2u9gCqKm25rD7ecukdhO5Agz8fowGYOpHCZEahuySFVa3Pwa8GutdLkbwZ l/4+oe6leNGkgQtRGgmYxpwJwvNMMUVTDdDOWFS2CKCgfcert5NLG9GqPm2u3FapDc ClFH24uZFs+dVYQRI1SVcoLeMfMus3hcFGBKb6Do= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Willy Tarreau , Johan Hovold Subject: [PATCH 4.4 11/25] USB: serial: ch341: fix character loss at high transfer rates Date: Fri, 13 Aug 2021 17:06:35 +0200 Message-Id: <20210813150521.087346803@linuxfoundation.org> X-Mailer: git-send-email 2.32.0 In-Reply-To: <20210813150520.718161915@linuxfoundation.org> References: <20210813150520.718161915@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Willy Tarreau commit 3c18e9baee0ef97510dcda78c82285f52626764b upstream. The chip supports high transfer rates, but with the small default buffers (64 bytes read), some entire blocks are regularly lost. This typically happens at 1.5 Mbps (which is the default speed on Rockchip devices) when used as a console to access U-Boot where the output of the "help" command misses many lines and where "printenv" mangles the environment. The FTDI driver doesn't suffer at all from this. One difference is that it uses 512 bytes rx buffers and 256 bytes tx buffers. Adopting these values completely resolved the issue, even the output of "dmesg" is reliable. I preferred to leave the Tx value unchanged as it is not involved in this issue, while a change could increase the risk of triggering the same issue with other devices having too small buffers. I verified that it backports well (and works) at least to 5.4. It's of low importance enough to be dropped where it doesn't trivially apply anymore. Cc: stable@vger.kernel.org Signed-off-by: Willy Tarreau Link: https://lore.kernel.org/r/20210724152739.18726-1-w@1wt.eu Signed-off-by: Johan Hovold Signed-off-by: Greg Kroah-Hartman --- drivers/usb/serial/ch341.c | 1 + 1 file changed, 1 insertion(+) --- a/drivers/usb/serial/ch341.c +++ b/drivers/usb/serial/ch341.c @@ -585,6 +585,7 @@ static struct usb_serial_driver ch341_de .owner = THIS_MODULE, .name = "ch341-uart", }, + .bulk_in_size = 512, .id_table = id_table, .num_ports = 1, .open = ch341_open,