From mboxrd@z Thu Jan 1 00:00:00 1970 From: Illia Smyrnov Subject: Re: [PATCH 1/2] spi: spi-omap2-mcspi.c: Add dts for slave device configuration. Date: Thu, 6 Jun 2013 13:08:46 +0300 Message-ID: <51B05FAE.60508@ti.com> References: <1370432398-7796-1-git-send-email-illia.smyrnov@ti.com> <1370432398-7796-2-git-send-email-illia.smyrnov@ti.com> <20130605115734.GY31367@sirena.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: linux-doc-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Tony Lindgren , Kroah-Hartman , devicetree-discuss-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Rob Herring , Daniel Mack , Illia Smyrnov , Greg, Matthias Brugger , Rob Landley , Grant Likely , spi-devel-general-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org To: Mark Brown Return-path: In-Reply-To: <20130605115734.GY31367-GFdadSzt00ze9xe1eoZjHA@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 On 06/05/2013 02:57 PM, Mark Brown wrote: > On Wed, Jun 05, 2013 at 02:39:57PM +0300, Illia Smyrnov wrote: > >> +SPI Controller specific data in SPI slave nodes: >> +- The spi slave nodes can provide the following information which is used >> + by the spi controller: >> + - ti,spi-turbo-mode: Set turbo mode for this device. >> + > > What is turb mode and According to OMAP TRM [1] MCSPI turbo mode improves the throughput of the SPI interface when a single channel is enabled by allowing transfers until the shift register and the MCSPI_RXx register are full. I tested turbo mode using KS8851 SPI Ethernet controller on Blaze with OMAP4460 and nuttcp tool with -r for RX throughput measuring. Enabling turbo mode was increased throughput form 7.5538 Mbps to 8.3848 Mbps > why would we not want to just enable it all the > time? Turbo mode gives the expected results not for all cases. There are some limitations: - works only if a single channel is enabled (no effect when several channels are enable); - improves the throughput on RX direction only; - effective only when a transfer exceeds two words. For single SPI word transfers OMAP TRM [1] recommends deactivate turbo mode. So it is useful to have the property in DT, that allow us to switch turbo mode off/on for certain slave. > Based on this documentation it's not really possible to tell... > I will add turbo mode description to documentation in the next patch version [1]: http://www.ti.com/lit/ug/swpu235z/swpu235z.pdf ------------------------------------------------------------------------------ How ServiceNow helps IT people transform IT departments: 1. A cloud service to automate IT design, transition and operations 2. Dashboards that offer high-level views of enterprise services 3. A single system of record for all IT processes http://p.sf.net/sfu/servicenow-d2d-j