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=-10.0 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE, SPF_PASS,TVD_PH_BODY_ACCOUNTS_PRE,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 AD3ABC433DF for ; Thu, 18 Jun 2020 01:53:59 +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 7C8E322245 for ; Thu, 18 Jun 2020 01:53:59 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="bEb9OrsN"; dkim=fail reason="signature verification failed" (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="ESi6GQCC" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7C8E322245 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.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=E3pYUL6ajpcSdcExr3Q5HC15XGl6ZRMNbhDaL1Nw2TI=; b=bEb9OrsN3x9w2S ZGpQpIdSQXKnYCpNK6cTMNvF8e73sqch2oMdKLI/vtOdhr9eA8r4tIz0RfttUTO36UPyetdMy4dk0 iuhVoHZ4zsV8s+O4+R88hZCEycTGa0a3Q/8KWCBRCbmd6dVeoB8w3qGBpnr/xoj0pPd7kZzt1xfJW Dqmkxt85pLTz90Lo0XkquOYzn/gJHO/4FV8Wt5rTD8trSL01AoFyoLdKqLZrT5D8koh+c4o67vyTz aQG6gMITQkYQD1qC3nfuzqt3iAJRGIDWv24alznTijg/CigDZRSkVRxZDIO3+exCKXvo7e7euJeeD bBZaUczWKnoZZ6Sj6A4w==; 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 1jljkU-0005BC-ED; Thu, 18 Jun 2020 01:53:50 +0000 Received: from mail.kernel.org ([198.145.29.99]) by bombadil.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1jljGW-0006Ky-2c; Thu, 18 Jun 2020 01:22:57 +0000 Received: from sasha-vm.mshome.net (c-73-47-72-35.hsd1.nh.comcast.net [73.47.72.35]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id A066020B1F; Thu, 18 Jun 2020 01:22:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1592443370; bh=Eq1DcpXNBEZu/BqwZzcK+uB2YIFarNYs5ivrXYLr4uU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=ESi6GQCCQBMA/Crc6rCGnoKGZO/PQsOupHh42boP8MfuWeVhEyN0U3awrkRFt6vnZ /fx4NxDfTFg9y5sJqfRIgVKjVgKwz0PFglKmFFAnzMrfqvM2LeLkJPPZsapHA89+Ej uAf45wkj0e16cTKMIw3YKM/vvxyX17Yumu4kq/W4= From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: [PATCH AUTOSEL 4.19 024/172] serial: 8250: Fix max baud limit in generic 8250 port Date: Wed, 17 Jun 2020 21:19:50 -0400 Message-Id: <20200618012218.607130-24-sashal@kernel.org> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20200618012218.607130-1-sashal@kernel.org> References: <20200618012218.607130-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200617_182252_253842_26DB2B0F X-CRM114-Status: GOOD ( 12.80 ) 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: Sasha Levin , Thomas Bogendoerfer , linux-mips@vger.kernel.org, Paul Burton , Arnd Bergmann , Catalin Marinas , Russell King , Ralf Baechle , Alexey Malahov , Serge Semin , Long Cheng , linux-mediatek@lists.infradead.org, Maxime Ripard , linux-serial@vger.kernel.org, Greg Kroah-Hartman , Andy Shevchenko , Will Deacon , linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org From: Serge Semin [ Upstream commit 7b668c064ec33f3d687c3a413d05e355172e6c92 ] 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 Link: https://lore.kernel.org/r/20200506233136.11842-2-Sergey.Semin@baikalelectronics.ru Signed-off-by: Greg Kroah-Hartman Signed-off-by: Sasha Levin --- 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 5a04d4ddca73..20b799219826 100644 --- a/drivers/tty/serial/8250/8250_port.c +++ b/drivers/tty/serial/8250/8250_port.c @@ -2628,6 +2628,8 @@ 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 @@ -2636,7 +2638,7 @@ 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 -- 2.25.1 _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel