Zynq SD Standalone driver

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Last updated: Nov 14, 2024 by Paul P, Alvin

This page gives an overview of the bare-metal driver support for the Xilinx® LogiCORE™ IP Arasan SD 2.0 host controller.

Table of Contents

Introduction

The SD/SDIO controller communicates with SDIO devices, SD memory cards, and MMC cards with up to four data lines. On the SD interface, one (DAT0) or four (DAT0-DAT3) lines can be used for data transfer. The SDIO interface can be routed through the MIO multiplexer to the MIO pins or through the EMIO to Select IO pin in the PL. The controller can support SD and SDIO applications in a wide range of portable low-power applications such as 802.11 devices, GPS, WiMAX, UWB, and others.
The SD/SDIO controller is compatible with the standard SD Host Controller Specification Version 2.0 Part A2 with SDMA (single operation DMA), ADMA1 (4 KB boundary limited DMA), and ADMA2 (ADMA2 allows data of any location and any size to be transferred in a 32-bit system memory-scatter-gather DMA) support. The core also supports up to seven functions in SD1, SD4, but does not support SPI mode. The Zynq-7000 SoC is expected to work with eMMC devices because the protocol is the same as SD, but this has not been extensively verified. Users must be careful to meet all timing requirements as they might or might not comply with eMMC. It does support SD high-speed (SDHS) and SD High Capacity (SDHC) card standards. The user should be familiar with the SD2.0/SDIO 2.0 specifications. The SD/SDIO controller also supports MMC3.31 standard. eMMC flash memories are not primary boot devices for Zynq-7000
family, but can be used as secondary boot devices.
The SD/SDIO controller is accessed by the Arm processor via the AHB bus. The controller also includes a DMA unit with an internal FIFO to meet throughput requirements.
For more information, please refer Chapter 73: SD/SDIO Controller in Zynq TRM, which includes links to the official documentation and resource utilization.

Driver Sources

The source code for the driver is included with the Vitis Unified Software Platform installation, as well as being available in the Xilinx Github repository. 

Driver NamePath to VitisPath in Github
sdps

<Vitis Install Directory>/data/embedded/XilinxProcessorIPLib/drivers/sdps

https://github.com/Xilinx/embeddedsw/tree/master/XilinxProcessorIPLib/drivers/sdps/

Note: To view the sources for a particular release, use the rel-version tag in github.  For example, for the 2020.1 release, the proper version of the code is: https://github.com/Xilinx/embeddedsw/tree/xilinx-v2020.1/XilinxProcessorIPLib/drivers/sdps

The driver source code is organized into different folders.  The table below shows the sdps driver source organization. 

Directory
Description

doc

Provides the API and data structure details

data

Driver .tcl, .mdd and .yaml file

examples

Example applications that show how to use the driver features

src

Driver source files, make and cmakelists file

Note: AMD Xilinx embeddedsw build flow has been changed from 2023.2 release to adapt to the new system device tree based flow. For further information, refer to the wiki link Porting embeddedsw components to system device tree (SDT) based flow

The .yaml(in data folder) and CMakeLists.txt(in src folder) files are needed for the System Device Tree based flow. The Driver .tcl and .mdd files are for the older build flow which will be deprecated in future.

Driver Implementation

For a full list of features supported by this IP, please refer Chapter 73: SD/SDIO Controller in Zynq TRM.

Features

  • 1 or 4 bit bus width
  • Normal or High speed (and configurable clock)
  • ADMA2 transfers
  • Polled mode
  • Switch command
  • All ACMD’s and CMD’s involved in initialization and transfer states
  • Configurable block size
  • Error detection

Known issues and Limitations

  • Driver supports only polled mode.

Example Applications

Refer to the driver examples directory for various example applications that exercise the different features of the driver. Each application is linked in the table below. The following sections describe the usage and expected output of the various applications.  These example applications can be imported into the Vitis IDE from the Board Support Package settings tab. 

Links to Examples

Examples Path:
https://github.com/Xilinx/embeddedsw/tree/master/XilinxProcessorIPLib/drivers/sdps/examples

Test Name

Example Source

Description
SDPS Read and Write example without file system

xsdps_raw_example.c

This examples does basic raw read and write test from SD/eMMC device in Polled mode.
Read and Write example with file system (using XILFFS library)

xilffs_polled_example.c

This examples does basic file system read and write test from SD/eMMC device in Polled mode.

Example Application Usage

SDPS Read and Write example without file system

This examples does basic raw read and write test from SD/eMMC device in Polled mode.

Expected Output

SD Raw Read/ Write Test
Successfully ran SD Raw Read/ Write Test

Read and Write example with file system (using XILFFS library)

This examples does basic file system read and write test from SD/eMMC device in Polled mode.

Expected Output

SD Polled File System Example Test
Successfully ran SD Polled File System Example Test

Example Design Architecture

NA


Performance

SD card : Sandisk Ultra 16GB SDHC card

Zynq:

High speed20.54 MB/sec

Changelog

2024.2

https://github.com/Xilinx/embeddedsw/blob/xlnx_rel_v2024.2/doc/ChangeLog#L625

2024.1

https://github.com/Xilinx/embeddedsw/blob/xlnx_rel_v2024.1/doc/ChangeLog#L528

2023.2

https://github.com/Xilinx/embeddedsw/blob/xlnx_rel_v2023.2/doc/ChangeLog#L601

2023.1

None

2022.2

https://github.com/Xilinx/embeddedsw/blob/xlnx_rel_v2022.2/doc/ChangeLog#L140

2022.1

https://github.com/Xilinx/embeddedsw/blob/xlnx_rel_v2022.1/doc/ChangeLog#L98

2021.2

None

2021.1

None

2020.2

None

2020.1

None

2019.2

https://github.com/Xilinx/embeddedsw/blob/xilinx-v2019.2/doc/ChangeLog#L20

2019.1

None

2018.3

None

2018.2

None

2018.1

None

2017.4

https://github.com/Xilinx/embeddedsw/blob/xilinx-v2017.4/doc/ChangeLog#L18

2017.3

https://github.com/Xilinx/embeddedsw/blob/xilinx-v2017.3/doc/ChangeLog#L329

2017.2

None

2017.1

https://github.com/Xilinx/embeddedsw/blob/xilinx-v2017.1/doc/ChangeLog#L326

2016.4

https://github.com/Xilinx/embeddedsw/blob/xilinx-v2016.4/doc/ChangeLog#L44

2016.3

https://github.com/Xilinx/embeddedsw/blob/xilinx-v2016.3/doc/ChangeLog#L178

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