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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 12141C43334 for ; Wed, 29 Jun 2022 09:48:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233111AbiF2Jsu (ORCPT ); Wed, 29 Jun 2022 05:48:50 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33988 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233027AbiF2Jsq (ORCPT ); Wed, 29 Jun 2022 05:48:46 -0400 Received: from mga17.intel.com (mga17.intel.com [192.55.52.151]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 09AD03D1D7; Wed, 29 Jun 2022 02:48:45 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1656496125; x=1688032125; h=date:from:to:cc:subject:message-id:mime-version; bh=kR520z9Moq5dCNqgaHhzTffg8JxRytrsfPcAIOtwgTE=; b=iuy2Oc59R3Z5Thts1yxX9y/5DH0xiWyLPRX9nQHI+cM1cJM9O88loWYP l6a28CwwKBowY2tbY0N98EuGJ0a6u0XoWdVA2hbUI0s3jE6OSz8zK1p4T pAiQZ87uEtbDfzNJByTttNWb0MV7UKf5iUpjgEwHvW1TYLSqFZrsthDwg tAswB5PEksuOFljFDqE+BTdmgyeq0BhtlCm6ZIKE8idsNwyvlXXE1qjCF uQegklAY4DRk7YkHp7ZhmCfBZIVll9FZvEvGgD9qLCSYR/D96bfDpvMec 9+j+ab0aHXxozUN83B+qdvSsseBH0IzPAhvL4Tq9CVJwD58zKdXIgyGMU g==; X-IronPort-AV: E=McAfee;i="6400,9594,10392"; a="262395191" X-IronPort-AV: E=Sophos;i="5.92,231,1650956400"; d="scan'208";a="262395191" Received: from fmsmga008.fm.intel.com ([10.253.24.58]) by fmsmga107.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 29 Jun 2022 02:48:45 -0700 X-IronPort-AV: E=Sophos;i="5.92,231,1650956400"; d="scan'208";a="647322406" Received: from dsummer-mobl.ger.corp.intel.com ([10.252.38.121]) by fmsmga008-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 29 Jun 2022 02:48:43 -0700 Date: Wed, 29 Jun 2022 12:48:41 +0300 (EEST) From: =?ISO-8859-15?Q?Ilpo_J=E4rvinen?= To: Tony Lindgren , Greg Kroah-Hartman cc: Andy Shevchenko , Jiri Slaby , linux-serial , LKML Subject: [PATCH v2] serial: 8250: Fix PM usage_count for console handover Message-ID: MIME-Version: 1.0 Content-Type: multipart/mixed; boundary="8323329-1304406510-1656496125=:1529" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This message is in MIME format. The first part should be readable text, while the remaining parts are likely unreadable without MIME-aware tools. --8323329-1304406510-1656496125=:1529 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8BIT When console is enabled, univ8250_console_setup() calls serial8250_console_setup() before .dev is set to uart_port. Therefore, it will not call pm_runtime_get_sync(). Later, when the actual driver is going to take over univ8250_console_exit() is called. As .dev is already set, serial8250_console_exit() makes pm_runtime_put_sync() call with usage count being zero triggering PM usage count warning (extra debug for univ8250_console_setup(), univ8250_console_exit(), and serial8250_register_ports()): [ 0.068987] univ8250_console_setup ttyS0 nodev [ 0.499670] printk: console [ttyS0] enabled [ 0.717955] printk: console [ttyS0] printing thread started [ 1.960163] serial8250_register_ports assigned dev for ttyS0 [ 1.976830] printk: console [ttyS0] disabled [ 1.976888] printk: console [ttyS0] printing thread stopped [ 1.977073] univ8250_console_exit ttyS0 usage:0 [ 1.977075] serial8250 serial8250: Runtime PM usage count underflow! [ 1.977429] dw-apb-uart.6: ttyS0 at MMIO 0x4010006000 (irq = 33, base_baud = 115200) is a 16550A [ 1.977812] univ8250_console_setup ttyS0 usage:2 [ 1.978167] printk: console [ttyS0] printing thread started [ 1.978203] printk: console [ttyS0] enabled To fix the issue, call pm_runtime_get_sync() in serial8250_register_ports() as soon as .dev is set for an uart_port if it has console enabled. This problem became apparent only recently because 82586a721595 ("PM: runtime: Avoid device usage count underflows") added the warning printout. I confirmed this problem also occurs with v5.18 (w/o the warning printout, obviously). Fixes: bedb404e91bb ("serial: 8250_port: Don't use power management for kernel console") Reviewed-by: Andy Shevchenko Reviewed-by: Tony Lindgren Tested-by: Tony Lindgren Signed-off-by: Ilpo Järvinen --- v2: - Remove reference to reverted printk kthreads from the changelog - Collect rev/tested-bys drivers/tty/serial/8250/8250_core.c | 4 ++++ drivers/tty/serial/serial_core.c | 5 ----- include/linux/serial_core.h | 5 +++++ 3 files changed, 9 insertions(+), 5 deletions(-) diff --git a/drivers/tty/serial/8250/8250_core.c b/drivers/tty/serial/8250/8250_core.c index 57e86133af4f..2e83e7367441 100644 --- a/drivers/tty/serial/8250/8250_core.c +++ b/drivers/tty/serial/8250/8250_core.c @@ -23,6 +23,7 @@ #include #include #include +#include #include #include #include @@ -558,6 +559,9 @@ serial8250_register_ports(struct uart_driver *drv, struct device *dev) up->port.dev = dev; + if (uart_console_enabled(&up->port)) + pm_runtime_get_sync(up->port.dev); + serial8250_apply_quirks(up); uart_add_one_port(drv, &up->port); } diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c index 85ef7ef00b82..3161445504bc 100644 --- a/drivers/tty/serial/serial_core.c +++ b/drivers/tty/serial/serial_core.c @@ -2024,11 +2024,6 @@ static int uart_proc_show(struct seq_file *m, void *v) } #endif -static inline bool uart_console_enabled(struct uart_port *port) -{ - return uart_console(port) && (port->cons->flags & CON_ENABLED); -} - static void uart_port_spin_lock_init(struct uart_port *port) { spin_lock_init(&port->lock); diff --git a/include/linux/serial_core.h b/include/linux/serial_core.h index b7b86ee3cb12..9d8aa139b175 100644 --- a/include/linux/serial_core.h +++ b/include/linux/serial_core.h @@ -404,6 +404,11 @@ static const bool earlycon_acpi_spcr_enable EARLYCON_USED_OR_UNUSED; static inline int setup_earlycon(char *buf) { return 0; } #endif +static inline bool uart_console_enabled(struct uart_port *port) +{ + return uart_console(port) && (port->cons->flags & CON_ENABLED); +} + struct uart_port *uart_get_console(struct uart_port *ports, int nr, struct console *c); int uart_parse_earlycon(char *p, unsigned char *iotype, resource_size_t *addr, -- tg: (f287f971e256..) fix/console-usage_count (depends on: tty-next) --8323329-1304406510-1656496125=:1529--