mirror of
https://github.com/AsahiLinux/u-boot
synced 2024-11-18 18:59:44 +00:00
48 lines
1.6 KiB
Text
48 lines
1.6 KiB
Text
|
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.
|