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=-24.4 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,MENTIONS_GIT_HOSTING, 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 00CCAC07E99 for ; Mon, 12 Jul 2021 08:54:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id DCB5A60FF3 for ; Mon, 12 Jul 2021 08:54:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1356744AbhGLI5E (ORCPT ); Mon, 12 Jul 2021 04:57:04 -0400 Received: from mail.kernel.org ([198.145.29.99]:55268 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1353734AbhGLICt (ORCPT ); Mon, 12 Jul 2021 04:02:49 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 1C27261D01; Mon, 12 Jul 2021 07:57:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1626076626; bh=yl34efDrb24XuT3VJb6DWVhzQpYKxDJ2cvWcVXrEse8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=DuaTUcvRAGICzShtQBh9e+NDohBDFehD/lBdEraNCWl8biF89PRNpUGvjFFkyoZCm 5/u7FVBUU9H7t3i0xKhQCeWzvsY0DlFNiRaW7msc2bQNP6UAPnlk4H1emZ8+iona/Y 2+aKZGI9zSz329swGofzp8pKuVUkU4CvSuqQydYM= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, "Maciej W. Rozycki" , Sasha Levin Subject: [PATCH 5.13 724/800] serial: 8250: Actually allow UPF_MAGIC_MULTIPLIER baud rates Date: Mon, 12 Jul 2021 08:12:27 +0200 Message-Id: <20210712061043.779446371@linuxfoundation.org> X-Mailer: git-send-email 2.32.0 In-Reply-To: <20210712060912.995381202@linuxfoundation.org> References: <20210712060912.995381202@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: Maciej W. Rozycki [ Upstream commit 78bcae8616ac277d6cb7f38e211493948ed73e30 ] Support for magic baud rate divisors of 32770 and 32769 used with SMSC Super I/O chips for extra baud rates of 230400 and 460800 respectively where base rate is 115200[1] has been added around Linux 2.5.64, which predates our repo history, but the origin could be identified as commit 2a717aad772f ("Merge with Linux 2.5.64.") with the old MIPS/Linux repo also at: . Code that is now in `serial8250_do_get_divisor' was added back then to `serial8250_get_divisor', but that code would only ever trigger if one of the higher baud rates was actually requested, and that cannot ever happen, because the earlier call to `serial8250_get_baud_rate' never returns them. This is because it calls `uart_get_baud_rate' with the maximum requested being the base rate, that is clk/16 or 115200 for SMSC chips at their nominal clock rate. Fix it then and allow UPF_MAGIC_MULTIPLIER baud rates to be selected, by requesting the maximum baud rate of clk/4 rather than clk/16 if the flag has been set. Also correct the minimum baud rate, observing that these ports only support actual (non-magic) divisors of up to 32767 only. [1] "FDC37M81x, PC98/99 Compliant Enhanced Super I/O Controller with Keyboard/Mouse Wake-Up", Standard Microsystems Corporation, Rev. 03/27/2000, Table 31 - "Baud Rates", p. 77 Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Signed-off-by: Maciej W. Rozycki Link: https://lore.kernel.org/r/alpine.DEB.2.21.2105190412280.29169@angie.orcam.me.uk Signed-off-by: Greg Kroah-Hartman Signed-off-by: Sasha Levin --- drivers/tty/serial/8250/8250_port.c | 19 ++++++++++++++++--- 1 file changed, 16 insertions(+), 3 deletions(-) diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c index fc5ab2032282..ff3f13693def 100644 --- a/drivers/tty/serial/8250/8250_port.c +++ b/drivers/tty/serial/8250/8250_port.c @@ -2629,6 +2629,21 @@ static unsigned int serial8250_get_baud_rate(struct uart_port *port, struct ktermios *old) { unsigned int tolerance = port->uartclk / 100; + unsigned int min; + unsigned int max; + + /* + * Handle magic divisors for baud rates above baud_base on SMSC + * Super I/O chips. Enable custom rates of clk/4 and clk/8, but + * disable divisor values beyond 32767, which are unavailable. + */ + if (port->flags & UPF_MAGIC_MULTIPLIER) { + min = port->uartclk / 16 / UART_DIV_MAX >> 1; + max = (port->uartclk + tolerance) / 4; + } else { + min = port->uartclk / 16 / UART_DIV_MAX; + max = (port->uartclk + tolerance) / 16; + } /* * Ask the core to calculate the divisor for us. @@ -2636,9 +2651,7 @@ static unsigned int serial8250_get_baud_rate(struct uart_port *port, * slower than nominal still match standard baud rates without * causing transmission errors. */ - return uart_get_baud_rate(port, termios, old, - port->uartclk / 16 / UART_DIV_MAX, - (port->uartclk + tolerance) / 16); + return uart_get_baud_rate(port, termios, old, min, max); } /* -- 2.30.2