Direct Memory Access (DMA) Configuration for SiWx91x#

Direct Memory Access (DMA) support is available in Serial Peripheral Interface (SPI) and Inter-IC Sound (I2S) peripheral drivers for SiWx91x devices and can be enabled as needed. All peripheral-to-memory, memory-to-peripheral, and memory-to-memory transfer modes are supported, including scatter–gather operations.

DMA Driver Configuration#

SiWx91x devices provide two DMA controllers, each with a dedicated Zephyr driver:

Driver capabilities:

GPDMA supports transfers up to 4095 bytes per descriptor, compared to 1024 bytes per descriptor for UDMA.
Multiple burst sizes are supported in GPDMA, improving throughput for high-speed peripherals.
Scatter–gather transfers are supported by both UDMA and GPDMA.

The Kconfig option DMA_SILABS_SIWX91X_SG_BUFFER_COUNT configures the maximum number of RSI_UDMA_DESC_T used to represent the struct dma_block_config in a DMA transfer.

The Kconfig option GPDMA_SILABS_SIWX91X_DESCRIPTOR_COUNT configures the maximum number of RSI_GPDMA_DESC_T used to represent the struct dma_block_config in a DMA transfer.

SPI (GSPI)#

The SPI driver for the General Serial Peripheral Interface (GSPI) peripheral, which uses the silabs,gspi binding, can optionally use DMA for both blocking and asynchronous operations.

Configuration#

The Kconfig option SPI_SILABS_SIWX91X_GSPI_DMA_MAX_BLOCKS configures the maximum number of struct dma_block_config used to represent the transfers in a struct spi_buf_set.

Prerequisites#

Enable the GPDMA node in Devicetree:
```
&gpdma {
	status = "okay";
};
```
For GSPI instances that should use DMA, configure two dmas properties named tx and rx to connect to the appropriate GPDMA peripheral request signals.
```
&spi0 {
    dmas = <&gpdma 0 11>, <&gpdma 1 10>;
    dma-names = "tx", "rx";
};
```
For SPI instances that should not use DMA, do not include DMA configurations in their Devicetree node.
Set CONFIG_SPI_SILABS_SIWX91X_GSPI_DMA to y.
- This is selected automatically if CONFIG_SPI_ASYNC is y.
- Set manually if using blocking operations, and DMA support is desired.

I2S#

The driver for the I2S peripheral, using the silabs,siwx91x-i2s binding, uses DMA for write and read operations.

Prerequisites#

Enable the UDMA Devicetree node.
```
&dma0 {
	status = "okay";
};
```
For I2S instances that should use DMA, configure two dmas properties named tx and rx to connect to the appropriate UDMA peripheral channels.
```
&i2s0 {
	dmas =  <&dma0 15>, <&dma0 14>;
	dma-names = "tx", "rx";
};
```
DMA is mandatory for I2S, and only UDMA is supported for I2S transfers.
Configure I2S_SILABS_SIWX91X_DMA_MAX_BLOCKS.