From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757689Ab2CID7p (ORCPT ); Thu, 8 Mar 2012 22:59:45 -0500 Received: from na3sys009aog118.obsmtp.com ([74.125.149.244]:49560 "EHLO na3sys009aog118.obsmtp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757214Ab2CID7n (ORCPT ); Thu, 8 Mar 2012 22:59:43 -0500 Message-ID: <4F598028.5020509@ti.com> Date: Fri, 09 Mar 2012 09:29:36 +0530 From: Aneesh V User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.2.21) Gecko/20110831 Thunderbird/3.1.13 MIME-Version: 1.0 To: Greg KH CC: linux-kernel@vger.kernel.org, linux-omap@vger.kernel.org Subject: Re: [PATCH 0/8] Add TI EMIF SDRAM controller driver References: <1331222065-3579-1-git-send-email-aneesh@ti.com> <20120308205944.GB16644@kroah.com> In-Reply-To: <20120308205944.GB16644@kroah.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Friday 09 March 2012 02:29 AM, Greg KH wrote: > On Thu, Mar 08, 2012 at 09:24:17PM +0530, Aneesh V wrote: >> Add a driver for the EMIF SDRAM controller used in TI SoCs >> >> EMIF is an SDRAM controller that supports, based on its revision, >> one or more of LPDDR2/DDR2/DDR3 protocols.This driver adds support >> for LPDDR2. >> >> The driver supports the following features: >> - Calculates the DDR AC timing parameters to be set in EMIF >> registers using data from the device data-sheets and based >> on the DDR frequency. If data from data-sheets is not available >> default timing values from the JEDEC spec are used. These >> will be safe, but not necessarily optimal >> - API for changing timings during DVFS or at boot-up >> - Temperature alert configuration and handling of temperature >> alerts, if any for LPDDR2 devices >> * temperature alert is based on periodic polling of MR4 mode >> register in DDR devices automatically performed by hardware >> * timings are de-rated and brought back to nominal when >> temperature raises and falls respectively >> - Cache of calculated register values to avoid re-calculating >> them >> >> The driver will need some minor updates when it is eventually >> integrated with Dynamic Voltage and Frequency Scaling (DVFS). >> This can not be done now as DVFS support is not available in >> the mainline yet. > > What will need to be updated in it? The userspace interface or > something else? The driver will need to register notifiers with regulator framework and clock framework respectively for voltage and frequency notifications. Also a hook will be needed for initiating the hardware sequence for updating the AC timings. This process is under the control of Power Reset and Clock Management(PRCM) module of OMAP. > > Why not wait until that code is accepted, it should be going into 3.4, > right? As Paul mentioned Core DVFS may take longer time. Besides, EMIF driver is a pre-requisite for correct functioning of Core DVFS. thanks, Aneesh