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- 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
- controller 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.
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