README.ti_qspi_flash 1.6 KB

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