Zephyr Cadence SPI Driver Support

This page gives an overview of the Cadence SPI Zephyr driver which is available as part of the zephyr-amd repo.

HW Features

  1. Master mode

  2. Slave mode

  3. All SPI flash instructions

  4. Support for 3 slaves - can be extended using a 3 to 8 decoder

  5. Driver uses manual chip select and auto start options

  6. Programmable clock frequency, polarity, and phase

  7. Interrupt support

Design Notes

  • N/A

Implementation

Features Supported

  1. Master mode

  2. All SPI flash instructions

  3. Support for 3 slaves - can be extended using a 3 to 8 decoder

  4. Programmable clock frequency, polarity, and phase

  5. Driver uses manual chip select

  6. Auto start options / Manual start options

  7. Polled and Interrupt mode

  8. Synchronous

Missing Features

  1. Asynchronous

  2. Slave mode

Known Issues

  • N/A

Limitations

Kernel Configuration

CONFIG_FLASH=y
CONFIG_FLASH_PAGE_LAYOUT=y
CONFIG_MAIN_STACK_SIZE=2048

Device Tree

Example SPI Node

spi0: spi@f1970000 {
        compatible = "cdns,spi-r1p6";
        status = "okay";
        reg = <0xf1970000 0x1000>;
        interrupts = <GIC_SPI 24 IRQ_TYPE_LEVEL IRQ_DEFAULT_PRIORITY>;
        #address-cells = <1>;
        #size-cells = <0>;
        cdns,num-ss-bits = <0x3>;
        is-decoded-cs = <0x00>;
        clocks = <&spi_ref_clk>;
        flash@2 {
            compatible = "jedec,spi-nor";
            reg = <0x02>;
            spi-max-frequency = <8000000>;
            jedec-id = [ c2 25 36  ]; /*mx25u3235f*/
            size = <33554432>; /*32Mb*/
            has-dpd;
            t-enter-dpd = <10000>;
            t-exit-dpd = <35000>;
        };
};

spi_ref_clk: spi_ref_clk {
        compatible = "fixed-clock";
        clock-frequency = <199998001>;
        #clock-cells = <0> ;
};

Driver Stack Size

  • TBD

Test Platform

  • Tenzing2_se7 RPU

Test SoC Architecture

  • RPU - R52 Core

Testing Sequence

  • Build zephyr application for R52 core

    • west build -p -b <board> <sample application path>
      Flash Ztets: west build -p always -b tenzing2_se7_rpu tests/drivers/flash/common/ –force
      Flash Samples: west build -p always -b tenzing2_se7_rpu samples/drivers/spi_flash/ –force

  • Run zephyr elf on Tenzing2_se7 RPU

Example Tests

Test Name

Example Source

Description

Flash Ztest

tests/drivers/flash/common/

These tests focus on the correct functionality of the flash drivers, covering cases such as:

  • Reading and writing data to the flash device

  • Erasing the flash device

  • Handling out-of-bounds addresses and sizes

  • Correct error handling

Flash Example test

samples/drivers/spi_flash/

This example application performs basic Erase/Write/ Read on spi-nor flash using SPI driver

Code Coverage

Code coverage with flash z-tests and example tests:

  • Flash example test

    • Lines: 81.5%

    • Functions: 80.2%

    • Branches: 62.9%

  • Flash ztests

    • Lines: 81.5%

    • Functions: 80.2%

    • Branches: 60.6%

Expected Output

Connecting to device com0.  Use Ctrl-\ to escape.
*** Booting Zephyr OS build xilinx_v2024.2 ***
Running TESTSUITE flash_driver
===================================================================
Test will run on device flash@2
START - test_flash_fill
 PASS - test_flash_fill in 0.966 seconds
===================================================================
START - test_flash_flatten
 PASS - test_flash_flatten in 0.916 seconds
===================================================================
START - test_read_unaligned_address
 PASS - test_read_unaligned_address in 0.318 seconds
===================================================================
TESTSUITE flash_driver succeeded

------ TESTSUITE SUMMARY START ------

SUITE PASS - 100.00% [flash_driver]: pass = 3, fail = 0, skip = 0, total = 3 duration = 2.200 seconds

PASS - [flash_driver.test_flash_fill] duration = 0.966 seconds

PASS - [flash_driver.test_flash_flatten] duration = 0.916 seconds

PASS - [flash_driver.test_read_unaligned_address] duration = 0.318 seconds

------ TESTSUITE SUMMARY END ------

===================================================================

Performance Metric

  • TBA

Mainline Status

Not in mainline as of March 19, 2025.

Driver Source Path

  • drivers/spi/spi_cdns.c

Misra C Report

  • TBA