From patchwork Fri Feb 23 08:39:03 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Yicong Yang X-Patchwork-Id: 775814 Received: from szxga05-in.huawei.com (szxga05-in.huawei.com [45.249.212.191]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id D9B7118E10; Fri, 23 Feb 2024 08:43:30 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=45.249.212.191 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1708677814; cv=none; b=DH3et1E3Gy9pi93EoPauZ/No1Ab0PK6Rc+YMfGpfZVPvxPTFZjUwESa8dlwQdjpY5cYY9qD/xgddat2NAl4meR+T8/kcBnk0bcpZGTipbL+FTS5+KL/oHu4p0YIBbCzC8vuCerkgWd0NPFfq5FmrJkm5LzUZ1jq9SF09uM82ie0= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1708677814; c=relaxed/simple; bh=iLnJXvuR5lkNWwaRH7mn/a0WJs/BElzIKvl+E/YGsVo=; h=From:To:CC:Subject:Date:Message-ID:MIME-Version:Content-Type; b=LZhgZdh9t5hnrldkucy0/UZqzf56oIIF8iUeUtceUwZgvdfVBu4EpLauH0G74Pr8nYOpAmh7IpvYV9J9N7d5II9wtI3Ege/KuQWSqhRY92dn9K8wXQKRUM2zFRuSeocgmEG3qIlWnp23PafXljyNhTNndlfcLJtnAeYZh+Up5/c= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com; spf=pass smtp.mailfrom=huawei.com; arc=none smtp.client-ip=45.249.212.191 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=huawei.com Received: from mail.maildlp.com (unknown [172.19.88.214]) by szxga05-in.huawei.com (SkyGuard) with ESMTP id 4Th3Q52vzdz1h08B; Fri, 23 Feb 2024 16:41:17 +0800 (CST) Received: from canpemm500009.china.huawei.com (unknown [7.192.105.203]) by mail.maildlp.com (Postfix) with ESMTPS id C1E871A016B; Fri, 23 Feb 2024 16:43:27 +0800 (CST) Received: from localhost.localdomain (10.50.165.33) by canpemm500009.china.huawei.com (7.192.105.203) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.1.2507.35; Fri, 23 Feb 2024 16:43:27 +0800 From: Yicong Yang To: , , , , CC: , , , , , , , Subject: [PATCH v4] serial: port: Don't suspend if the port is still busy Date: Fri, 23 Feb 2024 16:39:03 +0800 Message-ID: <20240223083903.42129-1-yangyicong@huawei.com> X-Mailer: git-send-email 2.31.0 Precedence: bulk X-Mailing-List: linux-serial@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-ClientProxiedBy: dggems702-chm.china.huawei.com (10.3.19.179) To canpemm500009.china.huawei.com (7.192.105.203) From: Yicong Yang We accidently met the issue that the bash prompt is not shown after the previous command done and until the next input if there's only one CPU (In our issue other CPUs are isolated by isolcpus=). Further analysis shows it's because the port entering runtime suspend even if there's still pending chars in the buffer and the pending chars will only be processed in next device resuming. We are using amba-pl011 and the problematic flow is like below: Bash                                         kworker tty_write()   file_tty_write()     n_tty_write()       uart_write()         __uart_start()           pm_runtime_get() // wakeup waker             queue_work()                                     pm_runtime_work()                                                rpm_resume()                                                 status = RPM_RESUMING                                                 serial_port_runtime_resume()                                                   port->ops->start_tx()                                                     pl011_tx_chars()                                                       uart_write_wakeup()         […]         __uart_start()           pm_runtime_get() < 0 // because runtime status = RPM_RESUMING                                // later data are not commit to the port driver                                                 status = RPM_ACTIVE                                                 rpm_idle() -> rpm_suspend() This patch tries to fix this by checking the port busy before entering runtime suspending. A runtime_suspend callback is added for the port driver. When entering runtime suspend the callback is invoked, if there's still pending chars in the buffer then flush the buffer. Cc: Tony Lindgren Cc: Andy Shevchenko Cc: Jiri Slaby Fixes: 84a9582fd203 ("serial: core: Start managing serial controllers to enable runtime PM") Reviewed-by: Tony Lindgren Signed-off-by: Yicong Yang --- Change since v3: - Drop non-fix change in __serial_port_busy() - Use a boolen busy instead of ret per Jiri Link: https://lore.kernel.org/all/20240208075216.48915-1-yangyicong@huawei.com/ Change since v2: - Narrow the spinlock region per Andy - Make __serial_port_busy() return -EBUSY if port has pending chars per Andy Thanks. Link: https://lore.kernel.org/all/20240206073322.5560-1-yangyicong@huawei.com/ Change since v1: - Use port lock wrapper per John - Flush the pending chars and return -EBUSY per Tony. Thanks. Link: https://lore.kernel.org/all/20240204031957.58176-1-yangyicong@huawei.com/ drivers/tty/serial/serial_port.c | 27 ++++++++++++++++++++++++++- 1 file changed, 26 insertions(+), 1 deletion(-) diff --git a/drivers/tty/serial/serial_port.c b/drivers/tty/serial/serial_port.c index 88975a4df306..1843c9ef7c49 100644 --- a/drivers/tty/serial/serial_port.c +++ b/drivers/tty/serial/serial_port.c @@ -46,8 +46,33 @@ static int serial_port_runtime_resume(struct device *dev) return 0; } +static int serial_port_runtime_suspend(struct device *dev) +{ + struct serial_port_device *port_dev = to_serial_base_port_device(dev); + struct uart_port *port; + unsigned long flags; + bool busy; + + port = port_dev->port; + + if (port->flags & UPF_DEAD) + return 0; + + uart_port_lock_irqsave(port, &flags); + busy = __serial_port_busy(port); + if (busy) + port->ops->start_tx(port); + uart_port_unlock_irqrestore(port, flags); + + if (busy) + pm_runtime_mark_last_busy(dev); + + return busy ? -EBUSY : 0; +} + static DEFINE_RUNTIME_DEV_PM_OPS(serial_port_pm, - NULL, serial_port_runtime_resume, NULL); + serial_port_runtime_suspend, + serial_port_runtime_resume, NULL); static int serial_port_probe(struct device *dev) {