From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Zik Saleeba" Subject: Re: PXA270 SSPSFRM gates chip select ? Date: Wed, 13 Feb 2008 07:48:22 +1100 Message-ID: <33e9dd1c0802121248q43883d6r481cb6f054de1050@mail.gmail.com> References: <20080211174339.73ca7ed5.merrij3@rpi.edu> <33e9dd1c0802111454k5deeaa38o9d21cee610b79da7@mail.gmail.com> <200802111851.10155.david-b@pacbell.net> <47B11178.6090904@whoi.edu> <33e9dd1c0802111948u2256d0adj8caa478073795d78@mail.gmail.com> <47B12406.9040208@whoi.edu> <33e9dd1c0802112124y5ae8dd39ua9078f2b3878a018@mail.gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: David Brownell , spi-devel-general-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org, stephen-nl6u4wocdmy51APUEpUfAkEOCMrvLtNR@public.gmane.org To: "Ned Forrester" Return-path: In-Reply-To: <33e9dd1c0802112124y5ae8dd39ua9078f2b3878a018-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 Followup on this problem: I did some experimentation using workqueues differently in my serial-via-spi driver and it seems to have fixed the problem with poor throughput in the pxa2xx_spi driver. I was previously using the default workqueue in my serial driver but changed it to use separate workqueues. To my surprise this completely fixed the problem I was having with the pxa2xx_spi driver being slow to respond to dma_transfer_complete(). Presumably the extra load on the default shared workqueue was holding up the service tasklet in pxa2xx_spi. So thanks to all - the problem is resolved at last. For what it's worth I'm still getting a 90us chip select period for only 6us of actual SPI transfer for short requests but I think that's down to the speed of the processor and the driver overhead. Thanks everyone for all the suggestions you've offered in the last couple of days! Cheers, Zik ------------------------------------------------------------------------- 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/