From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Brownell Subject: Re: PXA270 SSPSFRM gates chip select ? Date: Mon, 11 Feb 2008 18:51:09 -0800 Message-ID: <200802111851.10155.david-b@pacbell.net> References: <20080211174339.73ca7ed5.merrij3@rpi.edu> <33e9dd1c0802111454k5deeaa38o9d21cee610b79da7@mail.gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: stephen-nl6u4wocdmy51APUEpUfAkEOCMrvLtNR@public.gmane.org To: spi-devel-general-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org Return-path: In-Reply-To: <33e9dd1c0802111454k5deeaa38o9d21cee610b79da7-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org> Content-Disposition: inline List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: spi-devel-general-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org Errors-To: spi-devel-general-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org List-Id: linux-spi.vger.kernel.org On Monday 11 February 2008, Zik Saleeba wrote: > While we're on the subject of the pxa2xx_spi driver, I've found that > it has incredibly slow throughput. The problem appears to be related to > the use of a tasklet in pumping messages. The initial setup and > transfer is quick but then the tasklet is started and a context switch > causes terrible latency. It takes around a millisecond for the tasklet > to get control at which point the chip select is released and the SPI > bus is available for the next transfer. This means that running as > hard as it can the bus is idle 99% of the time. I've experimented with > removing the tasklet from the driver and it does improve the situation > markedly. Got patch? :) - Dave ------------------------------------------------------------------------- This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2008. http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/