From mboxrd@z Thu Jan 1 00:00:00 1970 From: Johan Hovold Subject: Re: [PATCH] tty: serial_core: Fix the incorrect configuration of baud rate and data length at the console serial port resume Date: Tue, 14 May 2019 09:34:57 +0200 Message-ID: <20190514073457.GI9651@localhost> References: Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org To: Lanqing Liu , Rob Herring , Greg Kroah-Hartman Cc: baolin.wang@unisoc.com, baolin.wang@linaro.org, jslaby@suse.com, lanqing.liu@unisoc.com, linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org, chunyan.zhang@unisoc.com, orson.zhai@unisoc.com, zhang.lyra@gmail.com List-Id: linux-serial@vger.kernel.org On Thu, May 09, 2019 at 01:42:39PM +0800, Lanqing Liu wrote: > When userspace opens a serial port for console, uart_port_startup() > is called. This function assigns the uport->cons->cflag value to > TTY->termios.c_cflag, then it is cleared to 0. When the user space > closes this serial port, the TTY structure will be released, and at > this time uport->cons->cflag has also been cleared. > > On the Spreadtrum platform, in some special scenarios, like charging mode, > userspace needs to close the console, which means the uport->cons->cflag > has also been cleared. But printing logs is still needed in the kernel. So > when system enters suspend and resume, the console needs to be configure > the baud rate and data length of the serial port according to its own cflag > when resuming the console port. At this time, the cflag is 0, which will > cause serial port to produce configuration errors that do not meet user > expectations. This is actually yet another regression due to 761ed4a94582 ("tty: serial_core: convert uart_close to use tty_port_close") which incidentally removed the call to uart_shutdown() where the cflag was being saved precisely to avoid the problem you're describing: ae84db9661ca ("serial: core: Preserve termios c_cflag for console resume") Judging from a quick look it seems the xmit buf, which is released in that function may now be leaking too. > To fix this, assigning the TTY->termios.c_cflag value to uport->cons->cflag > before the userspace closes this console serial port. It will ensure that > the correct cflag value can be gotten when the console serial port was > resumed. Not sure this is the right fix, but I don't have time to look at this right now. Johan