From patchwork Tue Aug 10 17:29:43 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg Kroah-Hartman X-Patchwork-Id: 495766 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=-19.5 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=ham 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 A4B50C4320A for ; Tue, 10 Aug 2021 17:56:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8D21B60EB9 for ; Tue, 10 Aug 2021 17:56:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236390AbhHJR46 (ORCPT ); Tue, 10 Aug 2021 13:56:58 -0400 Received: from mail.kernel.org ([198.145.29.99]:52288 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237737AbhHJRyy (ORCPT ); Tue, 10 Aug 2021 13:54:54 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 52DBE6108C; Tue, 10 Aug 2021 17:44:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1628617473; bh=l8tU+aNvmiH3O6wifGTHLkYIXutAko7PDTr3+NYhIzc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=VHvcsE9rWTKFvW68eZ16EBIWZL+KhxU6kUZt6gDnLraShG9ndyX8M1Gbq8uI5JTKZ OMAC3Ggr+bDpLTh8zaqdDqw1SBHUQ1Q0XAgrNXi4IzxC1NC7PJMsRUuHQN8k9LADM0 x8cICHEUyHA92ajPKDUt6IjNfrpAVorTwWxDi/Zc= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Willy Tarreau , Johan Hovold Subject: [PATCH 5.13 075/175] USB: serial: ch341: fix character loss at high transfer rates Date: Tue, 10 Aug 2021 19:29:43 +0200 Message-Id: <20210810173003.403776370@linuxfoundation.org> X-Mailer: git-send-email 2.32.0 In-Reply-To: <20210810173000.928681411@linuxfoundation.org> References: <20210810173000.928681411@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: stable@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 @@ -851,6 +851,7 @@ 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,