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