Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759867AbYAHL5j (ORCPT ); Tue, 8 Jan 2008 06:57:39 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756662AbYAHL5W (ORCPT ); Tue, 8 Jan 2008 06:57:22 -0500 Received: from caramon.arm.linux.org.uk ([78.32.30.218]:50985 "EHLO caramon.arm.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756339AbYAHL5V (ORCPT ); Tue, 8 Jan 2008 06:57:21 -0500 Date: Tue, 8 Jan 2008 11:57:03 +0000 From: Russell King To: Linux Kernel List , Alan Cox , Andrew Morton Subject: Re: [PATCH: 2/2] [SERIAL] avoid stalling suspend if serial port won't drain Message-ID: <20080108115703.GA27179@flint.arm.linux.org.uk> References: <20080108115148.GB10546@flint.arm.linux.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20080108115148.GB10546@flint.arm.linux.org.uk> User-Agent: Mutt/1.4.2.1i Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2004 Lines: 54 Some ports seem to be unable to drain their transmitters on shut down. Such a problem can occur if the port is programmed for hardware imposed flow control, characters are in the FIFO but the CTS signal is inactive. Normally, this isn't a problem because most places where we wait for the transmitter to drain have a time-out. However, there is no timeout in the suspend path. Give a port 30ms to drain; this is an arbitary value chosen to avoid long delays if there are many such ports in the system, while giving a reasonable chance for a single port to drain. Should a port not drain within this timeout, issue a warning. Signed-off-by: Russell King diff --git a/drivers/serial/serial_core.c b/drivers/serial/serial_core.c index 3bb5d24..4ce219c 100644 --- a/drivers/serial/serial_core.c +++ b/drivers/serial/serial_core.c @@ -1977,6 +1977,7 @@ int uart_suspend_port(struct uart_driver *drv, struct uart_port *port) if (state->info && state->info->flags & UIF_INITIALIZED) { const struct uart_ops *ops = port->ops; + int tries; state->info->flags = (state->info->flags & ~UIF_INITIALIZED) | UIF_SUSPENDED; @@ -1990,9 +1991,14 @@ int uart_suspend_port(struct uart_driver *drv, struct uart_port *port) /* * Wait for the transmitter to empty. */ - while (!ops->tx_empty(port)) { + for (tries = 3; !ops->tx_empty(port) && tries; tries--) { msleep(10); } + if (!tries) + printk(KERN_ERR "%s%s%s%d: Unable to drain transmitter\n", + port->dev ? port->dev->bus_id : "", + port->dev ? ": " : "", + drv->dev_name, port->line); ops->shutdown(port); } -- Russell King Linux kernel 2.6 ARM Linux - http://www.arm.linux.org.uk/ maintainer of: -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/