From mboxrd@z Thu Jan 1 00:00:00 1970 From: Russell King - ARM Linux Subject: Re: patch "tty: serial: OMAP: ensure FIFO levels are set correctly in non-DMA" added to tty tree Date: Sat, 4 Feb 2012 20:07:44 +0000 Message-ID: <20120204200743.GC17309@n2100.arm.linux.org.uk> References: <20120203205401.5ddf241d@notabene.brown> <20120204163931.GH1275@n2100.arm.linux.org.uk> <20120204170114.GJ1275@n2100.arm.linux.org.uk> <20120204174715.GK1275@n2100.arm.linux.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from caramon.arm.linux.org.uk ([78.32.30.218]:56111 "EHLO caramon.arm.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754193Ab2BDUIF (ORCPT ); Sat, 4 Feb 2012 15:08:05 -0500 Content-Disposition: inline In-Reply-To: Sender: linux-serial-owner@vger.kernel.org List-Id: linux-serial@vger.kernel.org To: Paul Walmsley Cc: Grazvydas Ignotas , khilman@ti.com, NeilBrown , govindraj.raja@ti.com, tomi.valkeinen@ti.com, linux-serial@vger.kernel.org, linux-omap@vger.kernel.org, linux-arm-kernel@lists.infradead.org On Sat, Feb 04, 2012 at 12:24:07PM -0700, Paul Walmsley wrote: > On Sat, 4 Feb 2012, Russell King - ARM Linux wrote: > > > On Sat, Feb 04, 2012 at 10:22:27AM -0700, Paul Walmsley wrote: > > > No, that is not an example of a protocol with a retry. That is an example > > > of a protocol that has no provision for reliable data delivery. Sending a > > > new data string one second later is not a retry. > > > > > > In such situations, the system integrator would just use the UART in the > > > default (lossless) mode. And if they don't, they'll have to deal with the > > > consequences that they chose. Those of us who ship battery-powered Linux > > > devices are indeed capable of making this choice. > > > > Okay, lets see. You're making a battery powered Linux device. It has > > a standard RS232 serial port available, and you allow users to load > > 'apps' onto it. > > > > Do you run the serial ports in lossless mode? > > Not every serial port is available to arbitrary 'apps.'. Not every > battery-powered Linux device allows users to run arbitrary 'apps.' > > On devices that do allow users to load arbitrary 'apps,' and that allow > those 'apps' to have direct access to the serial ports, I personally > believe that system integrators should not change the default OMAP serial > setting, which is to run the serial ports in lossless mode. > > Here is another example. Suppose someone builds a GPS receiver with an > OMAP that is capable of sending NMEA position sentences, once per second, > to a remotely connected serial device. No receive traffic is expected on > that port. > > The position you seem to be advocating is that the mainline Linux kernel > should not support any ability to allow the system integrator to > affirmatively instruct the SoC to enter device idle between those position > sentences. This will cause the SoC to consume energy to losslessly > handle an incoming serial character that will never come. Is that really > what you're advocating? Stop procrastinating. Please answer my question. Then I'll answer yours.