u-boot/doc/SPI
Sourav Poddar 9ea09e2037 doc: SPI: Add qspi test details on AM43xx
This shows the log obtained while testing qspi on AM437x  board.

Signed-off-by: Sourav Poddar <sourav.poddar@ti.com>
Reviewed-by: Jagannadha Sutradharudu Teki <jaganna@xilinx.com>
2014-02-18 22:41:09 +05:30
..
README.dual-flash sf: Add dual memories support - DUAL_PARALLEL 2014-01-12 21:40:22 +05:30
README.ftssp010_spi_test spi: Add Faraday SPI controller support 2014-01-11 12:21:30 +05:30
README.sandbox-spi sandbox: spi: Add new SPI flash driver 2013-12-09 12:22:39 -07:00
README.sh_qspi_test spi: Add support SH Quad SPI driver 2013-12-18 23:23:41 +05:30
README.ti_qspi_am43x_test doc: SPI: Add qspi test details on AM43xx 2014-02-18 22:41:09 +05:30
README.ti_qspi_dra_test README: qspi usecase and testing documentation. 2013-10-07 17:55:52 +05:30
README.ti_qspi_flash README: qspi usecase and testing documentation. 2013-10-07 17:55:52 +05:30
status.txt doc: SPI: Update status.txt 2014-01-12 21:40:23 +05:30

QSPI U-boot support
------------------

Host processor is connected to serial flash device via qpsi
interface. QSPI is a kind of spi module that allows single,
dual and quad read access to external spi devices. The module
has a memory mapped interface which provide direct interface
for accessing data form external spi devices.

The one QSPI in the device is primarily intended for fast booting
from Quad SPI flash devices.

Usecase
-------

MLO/u-boot.img will be flashed from SD/MMC to the flash device
using serial flash erase and write commands. Then, switch settings
will be changed to qspi boot. Then, the ROM code will read MLO
from the predefined location in the flash, where it was flashed and
execute it after storing it in SDRAM. Then, the MLO will read
u-boot.img from flash and execute it from SDRAM.

SPI mode
-------
SPI mode uses mtd spi framework for transfer and reception of data.
Can be used in:
1. Normal mode: use single pin for transfers
2. Dual Mode: use two pins for transfers.
3. Quad mode: use four pin for transfer

Memory mapped read mode
-----------------------
In this, SPI controller is configured using configuration port and then
controler is switched to memory mapped port for data read.

Driver
------
drivers/qspi/ti_qspi.c
    - Newly created file which is responsible for configuring the
	qspi controller and also for providing the low level api which
	is responsible for transferring the datas from host controller
	to flash device and vice versa.

Testing
-------
A seperated file named README.dra_qspi_test has been created which gives all the
details about the commands required to test qspi at u-boot level.