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=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 28D09C433DF for ; Wed, 1 Jul 2020 22:37:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0BA282082F for ; Wed, 1 Jul 2020 22:37:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726366AbgGAWhV (ORCPT ); Wed, 1 Jul 2020 18:37:21 -0400 Received: from mail.baikalelectronics.com ([87.245.175.226]:49852 "EHLO mail.baikalelectronics.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726121AbgGAWhV (ORCPT ); Wed, 1 Jul 2020 18:37:21 -0400 Received: from localhost (unknown [127.0.0.1]) by mail.baikalelectronics.ru (Postfix) with ESMTP id 1F473803202A; Wed, 1 Jul 2020 22:37:18 +0000 (UTC) X-Virus-Scanned: amavisd-new at baikalelectronics.ru Received: from mail.baikalelectronics.ru ([127.0.0.1]) by localhost (mail.baikalelectronics.ru [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id DHd7Fb6uuWwY; Thu, 2 Jul 2020 01:37:16 +0300 (MSK) Date: Thu, 2 Jul 2020 01:37:13 +0300 From: Serge Semin To: Daniel Winkler CC: Serge Semin , , , Alexey Malahov , BlueZ , chromeos-bluetooth-upstreaming , , , Aaron Sierra , Andy Shevchenko , Greg Kroah-Hartman , Jiri Slaby , Lukas Wunner , Vignesh Raghavendra , Subject: Re: [PATCH v2 0/1] Revert "serial: 8250: Fix max baud limit in generic 8250 port" Message-ID: <20200701223713.gavale4aramu3xnb@mobilestation> References: <20200701211337.3027448-1-danielwinkler@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <20200701211337.3027448-1-danielwinkler@google.com> X-ClientProxiedBy: MAIL.baikal.int (192.168.51.25) To mail (192.168.51.25) Sender: linux-serial-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-serial@vger.kernel.org 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. -Sergey > > The driver is in the cros tree at drivers/bluetooth/hci_qca.c > and uses the serdev interface. Specifically, this is the > QCA_ROME chipset. > > > Daniel Winkler (1): > Revert "serial: 8250: Fix max baud limit in generic 8250 port" > > drivers/tty/serial/8250/8250_port.c | 4 +--- > 1 file changed, 1 insertion(+), 3 deletions(-) > > -- > 2.27.0.212.ge8ba1cc988-goog >