From patchwork Wed May 6 23:31:32 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Serge Semin X-Patchwork-Id: 11532023 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 4CECB14B4 for ; Wed, 6 May 2020 23:32:02 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 2980720735 for ; Wed, 6 May 2020 23:32:02 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="TPrYTb1Z" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 2980720735 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=baikalelectronics.ru Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:References:In-Reply-To: Message-ID:Date:Subject:To:From:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=46e5r038gU8dmbtO8X3IsfCSKMSZHv/euTLF2WiMQ4M=; b=TPrYTb1ZDEwtIA 6UAyiHN1Luc2In/Qgcw/aFWw6JEk3rQR7XTpvl8Q310iTK6JEOAh/P3z5D6RHnSySiV+rpUBciB7Z 3mCvszFWPz6zGB6jQWWwfs/A5GC/vX/bhVZoWMcjcVO9pPfgzo7nRME2mgN9BlCMxUEqXYyK8Dkw8 XIGXOmnYGYgQs0ccOWzoUAzNszG+LNNG8xPrQSBVHcdeMSFr5rqID5ZYtOHAhy9TpjSZC8DRgbUXX wjsl09YY4rWArRSOtIKj3CBoyoVWiEVQD81Lu4jkvm0KGCWKrxkibFPE7AX3C3nJgbcCBhR0mN3sO iqqJZjBE6OkaMHVfElfA==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jWTWA-00027U-SR; Wed, 06 May 2020 23:31:58 +0000 Received: from mx.baikalelectronics.com ([94.125.187.42] helo=mail.baikalelectronics.ru) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jWTW7-00024n-C4; Wed, 06 May 2020 23:31:57 +0000 Received: from localhost (unknown [127.0.0.1]) by mail.baikalelectronics.ru (Postfix) with ESMTP id 70B2C8030808; Wed, 6 May 2020 23:31:51 +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 MhBbxmp3w3vz; Thu, 7 May 2020 02:31:48 +0300 (MSK) From: Serge Semin To: Thomas Bogendoerfer , Greg Kroah-Hartman , Jiri Slaby , Long Cheng Subject: [PATCH v3 1/4] serial: 8250: Fix max baud limit in generic 8250 port Date: Thu, 7 May 2020 02:31:32 +0300 Message-ID: <20200506233136.11842-2-Sergey.Semin@baikalelectronics.ru> In-Reply-To: <20200506233136.11842-1-Sergey.Semin@baikalelectronics.ru> References: <20200323024611.16039-1-Sergey.Semin@baikalelectronics.ru> <20200506233136.11842-1-Sergey.Semin@baikalelectronics.ru> MIME-Version: 1.0 X-ClientProxiedBy: MAIL.baikal.int (192.168.51.25) To mail (192.168.51.25) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200506_163155_766990_F1298F16 X-CRM114-Status: GOOD ( 10.40 ) X-Spam-Score: 0.0 (/) X-Spam-Report: SpamAssassin version 3.4.4 on bombadil.infradead.org summary: Content analysis details: (0.0 points) pts rule name description ---- ---------------------- -------------------------------------------------- -0.0 SPF_PASS SPF: sender matches SPF record 0.0 SPF_HELO_NONE SPF: HELO does not publish an SPF Record 0.0 TVD_PH_BODY_ACCOUNTS_PRE The body matches phrases such as "accounts suspended", "account credited", "account verification" X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Maxime Ripard , Stefan Roese , linux-mips@vger.kernel.org, Paul Burton , Arnd Bergmann , Catalin Marinas , linux-kernel@vger.kernel.org, Russell King , Ralf Baechle , Alexey Malahov , Serge Semin , Mika Westerberg , Lukas Wunner , linux-mediatek@lists.infradead.org, Serge Semin , linux-serial@vger.kernel.org, Andy Shevchenko , Will Deacon , linux-arm-kernel@lists.infradead.org, Vignesh Raghavendra Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org Standard 8250 UART ports are designed in a way so they can communicate with baud rates up to 1/16 of a reference frequency. It's expected from most of the currently supported UART controllers. That's why the former version of serial8250_get_baud_rate() method called uart_get_baud_rate() with min and max baud rates passed as (port->uartclk / 16 / UART_DIV_MAX) and ((port->uartclk + tolerance) / 16) respectively. Doing otherwise, like it was suggested in commit ("serial: 8250_mtk: support big baud rate."), caused acceptance of bauds, which was higher than the normal UART controllers actually supported. As a result if some user-space program requested to set a baud greater than (uartclk / 16) it would have been permitted without truncation, but then serial8250_get_divisor(baud) (which calls uart_get_divisor() to get the reference clock divisor) would have returned a zero divisor. Setting zero divisor will cause an unpredictable effect varying from chip to chip. In case of DW APB UART the communications just stop. Lets fix this problem by getting back the limitation of (uartclk + tolerance) / 16 maximum baud supported by the generic 8250 port. Mediatek 8250 UART ports driver developer shouldn't have touched it in the first place notably seeing he already provided a custom version of set_termios() callback in that glue-driver which took into account the extended baud rate values and accordingly updated the standard and vendor-specific divisor latch registers anyway. Fixes: 81bb549fdf14 ("serial: 8250_mtk: support big baud rate.") Signed-off-by: Serge Semin Cc: Alexey Malahov Cc: Thomas Bogendoerfer Cc: Paul Burton Cc: Ralf Baechle Cc: Arnd Bergmann Cc: Long Cheng Cc: Andy Shevchenko Cc: Maxime Ripard Cc: Catalin Marinas Cc: Will Deacon Cc: Russell King Cc: linux-mips@vger.kernel.org Cc: linux-arm-kernel@lists.infradead.org Cc: linux-mediatek@lists.infradead.org Reviewed-by: Andy Shevchenko --- drivers/tty/serial/8250/8250_port.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c index f77bf820b7a3..4d83c85a7389 100644 --- a/drivers/tty/serial/8250/8250_port.c +++ b/drivers/tty/serial/8250/8250_port.c @@ -2615,6 +2615,8 @@ static unsigned int serial8250_get_baud_rate(struct uart_port *port, struct ktermios *termios, struct ktermios *old) { + unsigned int tolerance = port->uartclk / 100; + /* * Ask the core to calculate the divisor for us. * Allow 1% tolerance at the upper limit so uart clks marginally @@ -2623,7 +2625,7 @@ static unsigned int serial8250_get_baud_rate(struct uart_port *port, */ return uart_get_baud_rate(port, termios, old, port->uartclk / 16 / UART_DIV_MAX, - port->uartclk); + (port->uartclk + tolerance) / 16); } void