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dmarc=none (p=none dis=none) header.from=linuxfoundation.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-mediatek-bounces+patchwork-linux-mediatek=patchwork.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=merlin.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=5wj6SFlfltb6hg0eTRhBJM92oZ/piAI1DWA7eBBMZYs=; b=dzSmOPHSD3q85u3tDp2w8dzNN 4E45tQEcZ4lATJp+bQSNlExtoZf9ZqLvr0OiU55kTrhIOxAjAtzQ0eDgqWeSEuX4x166BFIGe+ukZ QFUQrwXpzoXbT0OObgs2fWHJTZVeSOCkHwNK4XMsKg/kP32MYEgamJimw2k6uQvNVExR79Pz+nZjx dwBCOMSKeKmkNEIeSmWmQ2Bv95Y8o36v5Qpp1Mmhe7S1ux26G10CmVzyNc5ckb/fLTm/zNTnHQXbe vbesrjtCz23XZTGUXYHkirTnLys9doLWzGIx9BGB5lIuKSY1vlgQae46hjNYdQvw8JQxdXThw2oGI NGX0R1v/w==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jnpdc-0002aX-GB; Tue, 23 Jun 2020 20:35:24 +0000 Received: from mail.kernel.org ([198.145.29.99]) by merlin.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1jnpdX-0002Zg-Vl; Tue, 23 Jun 2020 20:35:20 +0000 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 A099120781; Tue, 23 Jun 2020 20:35:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1592944519; bh=2iMwDS1An9dC4G19YW2gfnJl3ePuwVtPxhbtfj/wS2A=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=SdXAAnhahnCQOoW297egTPJInb03lKgnMHPkuyiH3qZyrB0Apghm80v5csiZuSt7F v6Y5NSTkmBVnFVTpCMtHmq5tfZYoCD/oL0Us4BrYgiKMBmLvxIZhq/FjoS62kUbQZU 3fxhqw3C/1xlnJWUhu8uXEbdwB9O21eSamFwvHlc= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Subject: [PATCH 4.19 021/206] serial: 8250: Fix max baud limit in generic 8250 port Date: Tue, 23 Jun 2020 21:55:49 +0200 Message-Id: <20200623195318.022918548@linuxfoundation.org> X-Mailer: git-send-email 2.27.0 In-Reply-To: <20200623195316.864547658@linuxfoundation.org> References: <20200623195316.864547658@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 X-Spam-Note: CRM114 invocation failed X-Spam-Score: -5.0 (-----) X-Spam-Report: SpamAssassin version 3.4.4 on merlin.infradead.org summary: Content analysis details: (-5.0 points) pts rule name description ---- ---------------------- -------------------------------------------------- -5.0 RCVD_IN_DNSWL_HI RBL: Sender listed at https://www.dnswl.org/, high trust [198.145.29.99 listed in list.dnswl.org] -0.0 SPF_PASS SPF: sender matches SPF record 0.0 SPF_HELO_NONE SPF: HELO does not publish an SPF Record 0.1 DKIM_SIGNED Message has a DKIM or DK signature, not necessarily valid -0.1 DKIM_VALID Message has at least one valid DKIM or DK signature 0.0 TVD_PH_BODY_ACCOUNTS_PRE The body matches phrases such as "accounts suspended", "account credited", "account verification" -0.0 DKIMWL_WL_HIGH DKIMwl.org - Whitelisted High sender X-BeenThere: linux-mediatek@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 , Sasha Levin , Thomas Bogendoerfer , linux-mips@vger.kernel.org, Arnd Bergmann , Paul Burton , Greg Kroah-Hartman , Russell King , stable@vger.kernel.org, Alexey Malahov , Serge Semin , Long Cheng , linux-mediatek@lists.infradead.org, Ralf Baechle , Catalin Marinas , Andy Shevchenko , Will Deacon , linux-arm-kernel@lists.infradead.org Sender: "Linux-mediatek" Errors-To: linux-mediatek-bounces+patchwork-linux-mediatek=patchwork.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 5a04d4ddca736..20b799219826e 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