1 QSPI U-Boot support 2 ------------------ 3 4 Host processor is connected to serial flash device via qpsi 5 interface. QSPI is a kind of spi module that allows single, 6 dual and quad read access to external spi devices. The module 7 has a memory mapped interface which provide direct interface 8 for accessing data form external spi devices. 9 10 The one QSPI in the device is primarily intended for fast booting 11 from Quad SPI flash devices. 12 13 Usecase 14 ------- 15 16 MLO/u-boot.img will be flashed from SD/MMC to the flash device 17 using serial flash erase and write commands. Then, switch settings 18 will be changed to qspi boot. Then, the ROM code will read MLO 19 from the predefined location in the flash, where it was flashed and 20 execute it after storing it in SDRAM. Then, the MLO will read 21 u-boot.img from flash and execute it from SDRAM. 22 23 SPI mode 24 ------- 25 SPI mode uses mtd spi framework for transfer and reception of data. 26 Can be used in: 27 1. Normal mode: use single pin for transfers 28 2. Dual Mode: use two pins for transfers. 29 3. Quad mode: use four pin for transfer 30 31 Memory mapped read mode 32 ----------------------- 33 In this, SPI controller is configured using configuration port and then 34 controller is switched to memory mapped port for data read. 35 36 Driver 37 ------ 38 drivers/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 44 Testing 45 ------- 46 A seperated file named README.dra_qspi_test has been created which gives all the 47 details about the commands required to test qspi at U-Boot level. 48
