From patchwork Mon Jan 25 18:39:40 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Greg Kroah-Hartman X-Patchwork-Id: 372381 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=-18.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER, INCLUDES_PATCH, MAILING_LIST_MULTI, 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 738FBC43331 for ; Tue, 26 Jan 2021 21:28:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 497202053B for ; Tue, 26 Jan 2021 21:28:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728068AbhAZEs2 (ORCPT ); Mon, 25 Jan 2021 23:48:28 -0500 Received: from mail.kernel.org ([198.145.29.99]:33228 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729986AbhAYSpi (ORCPT ); Mon, 25 Jan 2021 13:45:38 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id 4B83520665; Mon, 25 Jan 2021 18:45:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1611600322; bh=n75Q2tY6ZfNexKfok1s9pQn9mz47sj6JLbYAKUy6jNQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=C9Gwn/NyCaPQFCD+w5WxMyKINtGPngTYZdDLUUG/UxRqwXeDwcw3n4TlhBC4Zs5kJ pFQJM8mGT9tpOWYfNqjJd5IJL7hjDhYgiJxafiHn6rxBgUASgIOYWmoI5jp7ZGrqJw Kmf31CPJAmAhNc+8LbiOjiJ2i+jOnbU2Qr8IKf50= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, =?utf-8?q?Pali_Roh=C3=A1r?= Subject: [PATCH 5.4 58/86] serial: mvebu-uart: fix tx lost characters at power off Date: Mon, 25 Jan 2021 19:39:40 +0100 Message-Id: <20210125183203.502167744@linuxfoundation.org> X-Mailer: git-send-email 2.30.0 In-Reply-To: <20210125183201.024962206@linuxfoundation.org> References: <20210125183201.024962206@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Pali Rohár commit 54ca955b5a4024e2ce0f206b03adb7109bc4da26 upstream. Commit c685af1108d7 ("serial: mvebu-uart: fix tx lost characters") fixed tx lost characters at low baud rates but started causing tx lost characters when kernel is going to power off or reboot. TX_EMP tells us when transmit queue is empty therefore all characters were transmitted. TX_RDY tells us when CPU can send a new character. Therefore we need to use different check prior transmitting new character and different check after all characters were sent. This patch splits polling code into two functions: wait_for_xmitr() which waits for TX_RDY and wait_for_xmite() which waits for TX_EMP. When rebooting A3720 platform without this patch on UART is print only: [ 42.699� And with this patch on UART is full output: [ 39.530216] reboot: Restarting system Fixes: c685af1108d7 ("serial: mvebu-uart: fix tx lost characters") Signed-off-by: Pali Rohár Cc: stable Link: https://lore.kernel.org/r/20201223191931.18343-1-pali@kernel.org Signed-off-by: Greg Kroah-Hartman --- drivers/tty/serial/mvebu-uart.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) --- a/drivers/tty/serial/mvebu-uart.c +++ b/drivers/tty/serial/mvebu-uart.c @@ -648,6 +648,14 @@ static void wait_for_xmitr(struct uart_p (val & STAT_TX_RDY(port)), 1, 10000); } +static void wait_for_xmite(struct uart_port *port) +{ + u32 val; + + readl_poll_timeout_atomic(port->membase + UART_STAT, val, + (val & STAT_TX_EMP), 1, 10000); +} + static void mvebu_uart_console_putchar(struct uart_port *port, int ch) { wait_for_xmitr(port); @@ -675,7 +683,7 @@ static void mvebu_uart_console_write(str uart_console_write(port, s, count, mvebu_uart_console_putchar); - wait_for_xmitr(port); + wait_for_xmite(port); if (ier) writel(ier, port->membase + UART_CTRL(port));