SPI

The Serial Peripheral Interface (SPI) is a synchronous, full-duplex, 4-wire serial bus.

Signals

Signal	Description
MOSI	Controller data output, target data input
MISO	Controller data input, target data output
SCLK	Clock generated by the controller
CS	Chip-select (active low); up to 4 chip-select lines per bus

Transfer Modes by Subsystem

Subsystem	Transfer Modes	Max Speed	Notes
Linux	FIFO, CPU DMA, GSI	50 MHz	4–32 bits per word; up to 4 CS
Boot	FIFO only	50 MHz	Polling mode; GSI not supported
aDSP	Full/half duplex, synchronous	50 MHz	Raw bit-level; no framing or error checking

Interface Components

Device Tree Sources

Platform	File
Dragonwing IQ-9075	`arch/arm64/boot/dts/qcom/lemans.dtsi`

APIs

Subsystem	Header
Linux	`include/uapi/linux/spi/spidev.h`, `include/linux/spi/spi.h`
Boot	`boot_images/boot/QcomPkg/Include/SpiApi.h`
aDSP	`adsp_proc/core/api/buses/spi_api.h`

Software Configuration

Linux Device Tree Example

spi@a98000 {
    compatible = "qcom,geni-spi";
    reg = <0 0x00a98000 0 0x4000>;
    clocks = <&gcc GCC_QUPV3_WRAP1_S6_CLK>;
    clock-names = "se";
    pinctrl-names = "default";
    pinctrl-0 = <&qup_spi14_data_clk>, <&qup_spi14_cs>;
    interrupts = <GIC_SPI 368 IRQ_TYPE_LEVEL_HIGH>;
    #address-cells = <1>;
    #size-cells = <0>;
    power-domains = <&rpmhpd SC7280_CX>;
    interconnects = <&clk_virt MASTER_QUP_CORE_1 0 &clk_virt SLAVE_QUP_CORE_1 0>,
                    <&gem_noc MASTER_APPSS_PROC 0 &cnoc2 SLAVE_QUP_1 0>;
    interconnect-names = "qup-core", "qup-config";
    dmas = <&gpi_dma1 0 6 QCOM_GPI_SPI>,
           <&gpi_dma1 1 6 QCOM_GPI_SPI>;
    dma-names = "tx", "rx";
    status = "disabled";
};

GPIO pinctrl:

qup_spi14_data_clk: qup-spi14-data-clk-state {
    pins = "gpio56", "gpio57", "gpio58";
    function = "qup16";
};

qup_spi14_cs: qup-spi14-cs-state {
    pins = "gpio59";
    function = "qup16";
};

QUPAC Access Control

{ QUPV3_0_SE3, QUPV3_PROTOCOL_SPI, QUPV3_MODE_FIFO, AC_HLOS, TRUE,  TRUE, FALSE }, // CAN SPI
{ QUPV3_1_SE3, QUPV3_PROTOCOL_SPI, QUPV3_MODE_FIFO, AC_HLOS, FALSE, TRUE, TRUE  }, // LS1 SPI
{ QUPV3_1_SE4, QUPV3_PROTOCOL_SPI, QUPV3_MODE_GSI,  AC_TZ,   FALSE, TRUE, TRUE  }, // NFC ESE
{ QUPV3_1_SE6, QUPV3_PROTOCOL_SPI, QUPV3_MODE_GSI,  AC_HLOS, FALSE, TRUE, FALSE }, // FP

Configuration Steps

Enable kernel configurations

Edit kernel_platform/kernel/arch/arm64/configs/qcom_defconfig:

CONFIG_QCOM_GENI_SE=y
CONFIG_SPI_QCOM_GENI=m
CONFIG_SPI_SPIDEV=m
CONFIG_QCOM_GPI_DMA=m

Enable SPI node in device tree

&spi1 {
    status = "okay";
};

Compile and flash

Compile the kernel and device tree changes, then load images to the device.

Verification

Transfer spidev_test to device

scp spidev_test root@<IP address>:/usr
chmod 777 /usr/spidev_test

Run test

./spidev_test -D /dev/spidev1.0
./spidev_test -D /dev/spidev3.0

Expected output:

spi mode: 0x0
bits per word: 8
max speed: 500000 Hz (500 KHz)

Debugging

Enable Debug Logs

sudo su
mount -t debugfs none /sys/kernel/debug

echo -n "file spi-geni-qcom.c +p" > /sys/kernel/debug/dynamic_debug/control
echo -n "file qcom-geni-se.c +p" > /sys/kernel/debug/dynamic_debug/control
echo -n "file spidev.c +p" > /sys/kernel/debug/dynamic_debug/control
echo -n "file gpi.c +p" > /sys/kernel/debug/dynamic_debug/control

To disable:

echo -n "file spi-geni-qcom.c -p" > /sys/kernel/debug/dynamic_debug/control
echo -n "file spidev.c -p" > /sys/kernel/debug/dynamic_debug/control

Troubleshooting

SPI Device Not Detected (/dev/spidev* missing)

# Check kernel config
zcat /proc/config.gz | grep -E 'CONFIG_SPI_SPIDEV|CONFIG_SPI_QCOM_GENI'
# Expect: CONFIG_SPI_QCOM_GENI=m, CONFIG_SPI_SPIDEV=m

# Check kernel logs
dmesg | grep -i spi
dmesg | grep -i geni

Verify SPI node status is "okay" in device tree
Verify QUPAC_Access.c sets QUPV3_PROTOCOL_SPI, AC_HLOS, bLoad=TRUE

SPI Transfer Failures / Data Corruption

# Test at lower speed
./spidev_test -D /dev/spidev1.0 -s 1000000

# Test different clock modes
./spidev_test -D /dev/spidev1.0 -H   # CPHA
./spidev_test -D /dev/spidev1.0 -O   # CPOL

Check GPIO drive strength and pull configuration in pinctrl
Verify clock phase and polarity match the target device
Use oscilloscope to check signal integrity

GSI/DMA Mode Not Working

lsmod | grep gpi
echo -n "file gpi.c +p" > /sys/kernel/debug/dynamic_debug/control

Verify CONFIG_QCOM_GPI_DMA=m is enabled
Check dmas and dma-names properties in device tree
Verify QUPAC_Access.c sets QUPV3_MODE_GSI and bAllowFifo=FALSE

Multiple Chip Select Issues

Verify all CS pins are configured in pinctrl. Check device tree reg property:

spidev@0 { reg = <0>; };  /* CS0 */
spidev@1 { reg = <1>; };  /* CS1 */

Test explicitly:

./spidev_test -D /dev/spidev1.0   # CS0
./spidev_test -D /dev/spidev1.1   # CS1

Boot Subsystem SPI Not Working

Verify QUP wrapper node status is "okay" and serial engine node is "disabled"
Confirm FIFO_MODE = /bits/ 8 <1> (GSI not supported in boot)
Check protocol_supported includes SPI_SUPPORTED
Verify QUPAC_Access.c settings match boot requirements

Quick Diagnostic Commands

ls /dev/spi*                          # Check SPI device nodes
dmesg | grep -i spi                   # Kernel SPI messages
dmesg | grep -i geni                  # GENI driver messages
lsmod | grep spi                      # Loaded SPI modules
lsmod | grep gpi                      # GPI DMA module

IQ-9075 EVK

Signals

Transfer Modes by Subsystem

Interface Components

Device Tree Sources

APIs

Software Configuration

Linux Device Tree Example

QUPAC Access Control

Configuration Steps

Verification

Debugging

Enable Debug Logs

Troubleshooting

Quick Diagnostic Commands

Resources

​Signals

​Transfer Modes by Subsystem

​Interface Components

​Device Tree Sources

​APIs

​Software Configuration

​Linux Device Tree Example

​QUPAC Access Control

​Configuration Steps

​Verification

​Debugging

​Enable Debug Logs

​Troubleshooting

​Quick Diagnostic Commands

​Resources

Signals

Transfer Modes by Subsystem

Interface Components

Device Tree Sources

APIs

Software Configuration

Linux Device Tree Example

QUPAC Access Control

Configuration Steps

Verification

Debugging

Enable Debug Logs

Troubleshooting

Quick Diagnostic Commands

Resources