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1. Introduction
---------------
**SpiDxe** driver implements MARVELL_SPI_MASTER_PROTOCOL in order to manage SPI
controller on Marvell A8k boards. It exposes below functionalities:
- create and setup SPI slaves
- raw transfer over SPI bus
2. SpiDxe driver design
-----------------------
2.1 MARVELL_SPI_MASTER_PROTOCOL
-----------------------
First member of SPI_MASTER protocol is Init function, implemented for SPI
master controller initialization.
->Init()
//
//Initializes the host controller to execute SPI commands.
//
param[IN] This Pointer to the MARVELL_SPI_MASTER_PROTOCOL instance
return EFI_SUCCESS Opcode initialization on the SPI host
controller completed.
return EFI_ACCESS_DENIED The SPI configuration interface is
locked.
return EFI_OUT_OF_RESOURCES Not enough resource available to
initialize the device.
return EFI_DEVICE_ERROR Device error, operation failed.
********
SPI devices (slaves) do not support any kind of automatic discovery or
enumaration, so every device needs manual configuration, which may be done
with SetupDevice function.
->SetupDevice()
//
//Allocate and zero all fields in the SPI_DEVICE struct. Set the chip
//select, max frequency and transfer mode supported by slave device.
//
param[IN] Cs Chip select ID of the slave chip.
param[IN] MaxFreq Maximum SCK rate in Hz.
param[IN] Mode Clock polarity and clock phase.
return *SPI_DEVICE Pointer to new allocated struct SPI_DEVICE.
return NULL NULL pointer if any eroor occured.
********
Developers have to destroy all created SPI device structs (with FreeDevice
function) in order to prevent from memory leak.
->FreeDevice()
//
//Free any memory associated with a SPI device.
//
param[in] SpiDev Pointer to the SPI_DEVICE struct.
return EFI_SUCCESS Memory fried succesfully.
return EFI_DEVICE_ERROR Device error, operation failed.
********
Transfer function allows write/read raw bytes over SPI bus.
->Transfer()
//
//Perform transfer over SPI bus
//
param[in] This Pointer to the MARVELL_SPI_MASTER_PROTOCOL
instance.
param[in] Slave Pointer to the SPI_DEVICE struct.
param[in] DataByteCount Number of bytes in the data portion of
the SPI cycle.
param[in] DataOut Pointer to caller-allocated buffer
containing the data to send.
param[out] DataIn Pointer to caller-allocated buffer
where received data will be placed.
param[in] Flag Flags which indicate state of CS line
during/after transfer (see file
Drivers/Spi/Devices/A8kSpiFlash.h)
return EFI_SUCCESS Memory fried succesfully.
return EFI_DEVICE_ERROR Device error, operation failed.
*********
When working with SPI devices it is often necessary to perform "command and
address" transactions. It may be done via ReadWrite function.
->ReadWrite()
//
//Perform two steps transactions. First write Command, then read/write
//buffer
//
param[in] This Pointer to the MARVELL_SPI_MASTER_PROTOCOL
instance.
param[in] Slave Pointer to the SPI_DEVICE struct.
param[in] Cmd Pointer to caller-allocated buffer
containing the command to send.
param[in] CmdSize Size of command (in bytes).
param[in] DataOut Pointer to caller-allocated buffer
containing the data to send.
param[out] DataIn Pointer to caller-allocated buffer
where received data will be placed.
param[in] DataSize Number of bytes in the data portion of
the SPI cycle.
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