Messages in this thread |  | | | Date | Fri, 09 Mar 2012 09:29:36 +0530 | | From | Aneesh V <> | | Subject | Re: [PATCH 0/8] Add TI EMIF SDRAM controller driver |
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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
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