.. SPDX-License-Identifier: GPL-2.0

  
  ===============================
  TI EMIF SDRAM Controller Driver
  ===============================

  
  Author

  ======

  Aneesh V <aneesh@ti.com>
  
  Location

  ========

  driver/memory/emif.c
  
  Supported SoCs:

  ===============

  TI OMAP44xx
  TI OMAP54xx
  
  Menuconfig option:

  ==================

  Device Drivers
  	Memory devices
  		Texas Instruments EMIF driver
  
  Description
  ===========
  This driver is for the EMIF module available in Texas Instruments
  SoCs. EMIF is an SDRAM controller that, based on its revision,
  supports one or more of DDR2, DDR3, and LPDDR2 SDRAM protocols.
  This driver takes care of only LPDDR2 memories presently. The
  functions of the driver includes re-configuring AC timing
  parameters and other settings during frequency, voltage and
  temperature changes

  Platform Data (see include/linux/platform_data/emif_plat.h)
  ===========================================================

  DDR device details and other board dependent and SoC dependent
  information can be passed through platform data (struct emif_platform_data)

  - DDR device details: 'struct ddr_device_info'
  - Device AC timings: 'struct lpddr2_timings' and 'struct lpddr2_min_tck'
  - Custom configurations: customizable policy options through
    'struct emif_custom_configs'
  - IP revision
  - PHY type

  Interface to the external world
  ===============================

  EMIF driver registers notifiers for voltage and frequency changes
  affecting EMIF and takes appropriate actions when these are invoked.

  - freq_pre_notify_handling()
  - freq_post_notify_handling()
  - volt_notify_handling()
  
  Debugfs

  =======

  The driver creates two debugfs entries per device.

  - regcache_dump : dump of register values calculated and saved for all
    frequencies used so far.
  - mr4 : last polled value of MR4 register in the LPDDR2 device. MR4
    indicates the current temperature level of the device.