From mboxrd@z Thu Jan 1 00:00:00 1970 From: Shubhrajyoti Datta Subject: Re: [PATCH] SPI: SSP SPI Controller driver Date: Thu, 22 Nov 2012 12:31:38 +0530 Message-ID: References: <1353464203.20353.6.camel@bichao> <20121121122630.13fc2087@bob.linux.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: jun.d.chen-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org, ken.k.mills-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org, sylvain.centelles-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org, chao bi , spi-devel-general-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org To: Alan Cox Return-path: In-Reply-To: <20121121122630.13fc2087-Z/y2cZnRghHXmaaqVzeoHQ@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 Wed, Nov 21, 2012 at 5:56 PM, Alan Cox wrote: > On Wed, 21 Nov 2012 17:44:21 +0530 > Shubhrajyoti Datta wrote: > > > On Wed, Nov 21, 2012 at 7:46 AM, chao bi wrote: > > > > > + /* Create the PM_QOS request */ > > > + if (drv_context->quirks & QUIRKS_USE_PM_QOS) > > > + pm_qos_add_request(&drv_context->pm_qos_req, > > > + PM_QOS_CPU_DMA_LATENCY, > > > + PM_QOS_DEFAULT_VALUE); > > > > > > > What happens if the flag is not set if it is absolutely necessary for > > the driver it should not be a > > configurable option > > If you read through the code it's set only when the device is > Moorestown/Oaktrail based and only in slave mode. It is not necessary > in other configurations. > Thats what I was trying to understand. If I am not wrong the latency is time related. Why only some platforms / modes need it also the value is not speed dependent. My doubt is that the time taken for the dma will be more in lower speed so the latency constraint could be relaxed. Also the spi core today doesnt have slave mode support thats a different discussion altogether may be we can leave it for now. > > Alan > ------------------------------------------------------------------------------ Monitor your physical, virtual and cloud infrastructure from a single web console. Get in-depth insight into apps, servers, databases, vmware, SAP, cloud infrastructure, etc. Download 30-day Free Trial. Pricing starts from $795 for 25 servers or applications! http://p.sf.net/sfu/zoho_dev2dev_nov