OSPI Linux driver

Introduction

The Octal-SPI Flash Controller can be used to provide access to Serial Flash devices. Standard Serial Peripheral Interface (SPI) is supported along with high performance Octal SPI variants. The Octal-SPI Flash Controller transfer the data either in a memory mapped direct fashion or in an indirect fashion where the controller is set up via configuration registers to silently perform some requested operation, signalling its completion via interrupts or status registers. For indirect operations, data is transferred between system memory and external FLASH memory via an internal SRAM. OSPI has it’s own internal DMA which is used to read the data from the flash, SRAM is accessible only in case of DMA mode of operation (indirect mode).

In INDAC (Indirect Access Controller) mode DMA writes are not supported, Non-DMA, DAC or STIG modes are used for flash writes. In INDAC(DMA) mode only flash reads are supported.

Features Supported in HW

  1. Direct mode of memory mapped operation.
  2. Software triggered IO mode (STIG) up to 8-bytes of data transfers.
  3. Indirect DMA reads.
  4. NON-DMA read and write support
  5. Local SRAM to reduce AHB overhead.
  6. Supports SDR and DDR protocols.
  7. Programmable master mode clock frequencies.
  8. Serial clock with programmable polarity.
  9. Programmable peripheral selects (chip select).
  10. Support for Single and Octal instructions.
  11. Interrupts and polled based operations.

Features supported in driver

  1. Software triggered IO mode (STIG) up to 8-bytes of data transfers.
  2. INDAC DMA reads.
  3. SDR and DDR mode support.
  4. Support for Octal mode.
  5. Interrupt based transfers.
  6. RX Tuning support for PHY modes.
  7. NON-DMA read and write support.

Driver Missing features, Known Issues and Limitations

  • STIG Memory Bank.

Supported Flash parts

  • Micron (512Mb, 1Gb and 2Gb)

Testing

  • Flashcp
  • mtd utilities.
  • mtd_speedtest
  • mtd_stresstest
  • File System testing - UBIFS and JFFS2

Kernel Configuration

Device-tree

Sample Device-tree node for OSPI 

Performance Details

At frequency 133.33 MHz

DDR mode:

Read Speed: 226768 KiB/s

Write Speed: 1696 KiB/s

Mainline Status

Not in Mainline

Change Log

2021.1

  • b832b6b - Added support for OSPI Macronix(mx25um51345g) part .
  • 7216a02 - Added support for reading from unaligned address.
  • 5ca8ce8 - Rx periodic tuning updates for Master DLL mode.

2020.2

  • 6ab15b2 - Added support for stacked mode.
  • 3ff8d4e, 46fe093 - Added support for ISSI and GIGADEVICE parts.
  • 56e44ec - Fix the issues in Rx periodic tuning.

2020.1

  • 508f0df, e0d688d - Added support for UBIFS and JFFS2 file system support.
  • 40ede36 - Added support for NON-DMA read and write support.
  • f73c158 - Added support for RX periodic tuning (periodicity of 5 minutes). 

2019.2

  • New driver