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=-1.0 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS autolearn=no 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 A39A8C433E0 for ; Thu, 2 Jul 2020 07:37:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 800AD2089D for ; Thu, 2 Jul 2020 07:37:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1593675437; bh=vpifWVwgbjHSUaEegAAHzDiKupI4P46wI+RPjm/wU9M=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=FYVSv6ygJeHzRJVLSuVwPhPdXnO+i+TnmxbRbGyI9E4qcvvG9eO2pUzL3Lg5pirFI DKjij70q+spAhUz2EKv8JERBGsY/cU0Hn5JTR5CmE0ZwrDCuaSMhbipfiuwXtaoNL/ PpRGUuzLlvLESlAQQghkz0JsEvUDxtwQ+EsQOb4I= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727059AbgGBHhR (ORCPT ); Thu, 2 Jul 2020 03:37:17 -0400 Received: from mail.kernel.org ([198.145.29.99]:33360 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726630AbgGBHhQ (ORCPT ); Thu, 2 Jul 2020 03:37:16 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 8A27F2085B; Thu, 2 Jul 2020 07:37:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1593675436; bh=vpifWVwgbjHSUaEegAAHzDiKupI4P46wI+RPjm/wU9M=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=KmcMFIrPlH/DYGVA69kjk8PKCY/DCTSfxA7mi8F7SUmgwxhtcI3ae4CZwpCU359bq O48jck5Plf9ZR0KbrKdFvmTivRigbjS7x7dcIjocdZd0fcyNBPP6IoFm28o+ZJ2gwT rN71msrjI6cYKrnS0UT2QSDl1Lxr4H8miKM1euLk= Date: Thu, 2 Jul 2020 09:37:20 +0200 From: Greg Kroah-Hartman To: Serge Semin Cc: Daniel Winkler , Serge Semin , linux-serial@vger.kernel.org, linux-mediatek@lists.infradead.org, Alexey Malahov , BlueZ , chromeos-bluetooth-upstreaming , stable@vger.kernel.org, abhishekpandit@chromium.org, Aaron Sierra , Andy Shevchenko , Jiri Slaby , Lukas Wunner , Vignesh Raghavendra , linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 0/1] Revert "serial: 8250: Fix max baud limit in generic 8250 port" Message-ID: <20200702073720.GE1073011@kroah.com> References: <20200701211337.3027448-1-danielwinkler@google.com> <20200701223713.gavale4aramu3xnb@mobilestation> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200701223713.gavale4aramu3xnb@mobilestation> Sender: linux-serial-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-serial@vger.kernel.org On Thu, Jul 02, 2020 at 01:37:13AM +0300, Serge Semin wrote: > On Wed, Jul 01, 2020 at 02:13:36PM -0700, Daniel Winkler wrote: > > > > This change regresses the QCA6174A-3 bluetooth chip, preventing > > firmware from being properly loaded. Without this change, the > > chip works as intended. > > > > The device is the Kukui Chromebook using the Mediatek chipset > > and the 8250_mtk uart. Initial controller baudrate is 115200 > > and operating speed is 3000000. Our entire suite of bluetooth > > tests now fail on this platform due to an apparent failure to > > sync its firmware on initialization. > > Ok. It's mediatek 8250 driver, which is responsible for the failure. > Then we'll have two options: > > 1) Add a new capability like UART_CAP_NO16DIV and take it into account > in the serial8250_get_baud_rate() method. > > I don't have a documentation for the Mediatek UART port, but it seems to me > that that controller calculates the baud rate differently from the standard > 8250 port. A standard 8250 port does that by the next formulae: > baud = uartclk / (16 * divisor). > While it seems to me that the Mediatek port uses the formulae like: > baud = uartclk / divisor. (Please, correct me if I'm wrong) > If so, then we could introduce a new capability like UART_CAP_NO16DIV. The > 8250_mtk driver will add it to the 8250-port capabilities field. The > serial8250_get_baud_rate() method should be altered in a way so one would check > whether the UART_CAP_NO16DIV flag is set and if it is then the > uart_get_baud_rate() function will be called without uartclk normalized by the > factor of 16. > > 2) Manually call serial8250_do_set_divisor() in the custom set_termios() > callback. > > Just add the uart_update_timeout() and serial8250_do_set_divisor() methods > invocation into the mtk8250_set_termios() function, which the original commit > 81bb549fdf14 ("serial: 8250_mtk: support big baud rate") author should have > done in the first place. Sounds like a sane fix, thanks for looking into this. greg k-h