From patchwork Thu Apr 7 08:13:53 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Yu Tu X-Patchwork-Id: 12804743 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org 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 smtp.lore.kernel.org (Postfix) with ESMTPS id 8B22FC433F5 for ; Thu, 7 Apr 2022 08:45:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:References:In-Reply-To: Message-ID:Date:Subject:CC:To:From:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=LBzXP04xjNhjFeeyJLiAAhcAq4lYcKPZWEBXybidhlo=; b=DMhHo5jhfmhUCt vaY12fHBbOstNEXlhkf4gJhlknOHnJeaCsRs6l2Kwl6zfkSefyM5FLULPkVeVUMxE4WErWqYA3s5Q ZhQGLFipeWDXrP7uqSJjRj6HwSPKbu0epDxIJ0qkATq3MazNwKxUOnLQnr2NsdW173jnOZjNSHcLi MBg9YY02PHvuG5k9ld3e9ytRivCUfX503rDUkdaAVdO91QNu3SNrNM9BCn95Df70TgvB14cf85aAS vGn0HNU8nBuqBZ3sA5YfeNXahX2Rsr1yBEBqpu4wbvbFd7T+Y8G16O4M1YiVt+TMOWXv4mpOKGAs+ zAlwuFEWfpj0kFNNYvQQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1ncNlX-00AXPg-Jp; Thu, 07 Apr 2022 08:45:19 +0000 Received: from mail-sh.amlogic.com ([58.32.228.43]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1ncNIb-00AIfm-MC; Thu, 07 Apr 2022 08:15:29 +0000 Received: from droid06.amlogic.com (10.18.11.248) by mail-sh.amlogic.com (10.18.11.5) with Microsoft SMTP Server id 15.1.2176.14; Thu, 7 Apr 2022 16:15:22 +0800 From: Yu Tu To: , , , , Neil Armstrong , Kevin Hilman , Jerome Brunet CC: Greg Kroah-Hartman , Jiri Slaby , Martin Blumenstingl , Yu Tu Subject: [PATCH 1/3] tty: serial: meson: Use DIV_ROUND_CLOSEST to calculate baud rates Date: Thu, 7 Apr 2022 16:13:53 +0800 Message-ID: <20220407081355.13602-2-yu.tu@amlogic.com> X-Mailer: git-send-email 2.33.1 In-Reply-To: <20220407081355.13602-1-yu.tu@amlogic.com> References: <20220407081355.13602-1-yu.tu@amlogic.com> MIME-Version: 1.0 X-Originating-IP: [10.18.11.248] X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20220407_011525_824983_71CFCB4E X-CRM114-Status: UNSURE ( 8.12 ) X-CRM114-Notice: Please train this message. X-BeenThere: linux-amlogic@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-amlogic" Errors-To: linux-amlogic-bounces+linux-amlogic=archiver.kernel.org@lists.infradead.org Due to chip process differences, chip designers recommend using baud rates as close to and larger as possible in order to reduce clock errors. Signed-off-by: Yu Tu Reviewed-by: Neil Armstrong --- drivers/tty/serial/meson_uart.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/tty/serial/meson_uart.c b/drivers/tty/serial/meson_uart.c index 2bf1c57e0981..8e59624935af 100644 --- a/drivers/tty/serial/meson_uart.c +++ b/drivers/tty/serial/meson_uart.c @@ -299,10 +299,10 @@ static void meson_uart_change_speed(struct uart_port *port, unsigned long baud) cpu_relax(); if (port->uartclk == 24000000) { - val = ((port->uartclk / 3) / baud) - 1; + val = DIV_ROUND_CLOSEST(port->uartclk / 3, baud) - 1; val |= AML_UART_BAUD_XTAL; } else { - val = ((port->uartclk * 10 / (baud * 4) + 5) / 10) - 1; + val = DIV_ROUND_CLOSEST(port->uartclk / 4, baud) - 1; } val |= AML_UART_BAUD_USE; writel(val, port->membase + AML_UART_REG5);