From mboxrd@z Thu Jan 1 00:00:00 1970 From: Julien Boibessot Subject: Re: SPI: Add SPI driver for most known i.MX SoCs Date: Tue, 02 Jun 2009 10:13:22 +0200 Message-ID: <4A24DF22.4040601@free.fr> References: <20090504214307.GN15603@pengutronix.de> Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Cc: spi-devel-general-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org, linux-arm-kernel-xIg/pKzrS19vn6HldHNs0ANdhmdF6hFW@public.gmane.org To: Sascha Hauer Return-path: In-Reply-To: <20090504214307.GN15603-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: spi-devel-general-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org List-Id: linux-spi.vger.kernel.org Hi Sascha, I finally had some time to test your new unified SPI driver on my i.MX27 = platform... It's a good idea to have a common SPI driver for all MXs but I have two = remarks: Sascha Hauer a =E9crit : > While there already is a SPI driver for i.MX1 in the tree there are > good reasons to replace it: > > - The inkernel driver implements a full blown SPI driver, but > the hardware can be fully supported using a bitbang driver. > This greatly reduces the size and complexity of the driver. > = I don't know yet if it's related to bitbang but I would say that your = driver is 2x slowier that current inkernel one. We (armadeus) have i.MXL = and i.MX27 boards with ADC, Touchscreen and CAN bus on SPI and saw a = lost of performance with your driver (when fast successive SPI transfers = are needed). You probably won't notice it if you only have a Freescale's = power chip or an EEPROM connected to your SPI bus. Sorry but I didn't had time yet to investigate more :-(. I know that I can't have the official Linux kernel suited for my = particular needs (;-) ), so what would be the things to do to improve = your driver performances ? > - The DMA API of the durrent driver is broken for arch-mx1 (as opposed > to arch-imx) and nobody cared to fix it yet. > = Will your driver use DMA in a near future ? Regards, Julien ---------------------------------------------------------------------------= --- OpenSolaris 2009.06 is a cutting edge operating system for enterprises = looking to deploy the next generation of Solaris that includes the latest = innovations from Sun and the OpenSource community. Download a copy and = enjoy capabilities such as Networking, Storage and Virtualization. = Go to: http://p.sf.net/sfu/opensolaris-get