From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sebastian Andrzej Siewior Subject: Re: [PATCH 3/3] serial: 8250: omap: restore registers on shutdown Date: Thu, 06 Aug 2015 15:59:34 +0200 Message-ID: <55C36846.8010104@linutronix.de> References: <87egjp2r4a.fsf@linutronix.de> <55BAC67E.1010400@hurleysoftware.com> <20150803160937.GA26497@linutronix.de> <55BF980E.20908@hurleysoftware.com> <55BF9CE0.4080107@linutronix.de> <55BFC1BA.5020605@hurleysoftware.com> <55C0A8F4.4010204@linutronix.de> <55C352A8.3070102@hurleysoftware.com> <55C3539F.4070403@linutronix.de> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Return-path: In-Reply-To: <55C3539F.4070403@linutronix.de> Sender: linux-kernel-owner@vger.kernel.org To: Peter Hurley Cc: John Ogness , linux-kernel@vger.kernel.org, Greg Kroah-Hartman , Tony Lindgren , linux-omap@vger.kernel.org, nsekhar@ti.com, nm@ti.com, linux-serial@vger.kernel.org, Heikki Krogerus List-Id: linux-serial@vger.kernel.org On 08/06/2015 02:31 PM, Sebastian Andrzej Siewior wrote: Hi Peter, >> I'll look at/test this this weekend, ok? > > Sure. I'm currently re-spinning the patches so have everything in > proper pieces. While at it I will take a look at x_char. So now that I actually look at it. If I read this right, we never send the x_char if the TX-DMA never fails to do its job. The comment above uart_send_xchar() says it is high priority. What do you suggest, wait until the transfer completes, send the x_char _or_ pause the transfer send that byte and then send the byte? In both cases we have to wait until for the FIFO-empty interrupt to make sure we don't overrun that TX-FIFO. I *think* waiting until the transfer completes would be simpler but it is not necessarily high priority. >> Regards, >> Peter Hurley Sebastian