1QSPI U-boot support 2------------------ 3 4Host processor is connected to serial flash device via qpsi 5interface. QSPI is a kind of spi module that allows single, 6dual and quad read access to external spi devices. The module 7has a memory mapped interface which provide direct interface 8for accessing data form external spi devices. 9 10The one QSPI in the device is primarily intended for fast booting 11from Quad SPI flash devices. 12 13Usecase 14------- 15 16MLO/u-boot.img will be flashed from SD/MMC to the flash device 17using serial flash erase and write commands. Then, switch settings 18will be changed to qspi boot. Then, the ROM code will read MLO 19from the predefined location in the flash, where it was flashed and 20execute it after storing it in SDRAM. Then, the MLO will read 21u-boot.img from flash and execute it from SDRAM. 22 23SPI mode 24------- 25SPI mode uses mtd spi framework for transfer and reception of data. 26Can be used in: 271. Normal mode: use single pin for transfers 282. Dual Mode: use two pins for transfers. 293. Quad mode: use four pin for transfer 30 31Memory mapped read mode 32----------------------- 33In this, SPI controller is configured using configuration port and then 34controler is switched to memory mapped port for data read. 35 36Driver 37------ 38drivers/qspi/ti_qspi.c 39 - Newly created file which is responsible for configuring the 40 qspi controller and also for providing the low level api which 41 is responsible for transferring the datas from host controller 42 to flash device and vice versa. 43 44Testing 45------- 46A seperated file named README.dra_qspi_test has been created which gives all the 47details about the commands required to test qspi at u-boot level. 48