Re: [PATCH SPI for-next 2/3] spi: mchp-pci1xxxx: DMA Read support for copying data into SPI Buf

[Mark Brown]

On Fri, Dec 15, 2023 at 05:17:47PM +0530, Thangaraj Samynathan wrote:

> +	tx_dma_addr = dma_map_single(dev, (void *)xfer->tx_buf, xfer->len, DMA_TO_DEVICE);
> +	if (dma_mapping_error(NULL, tx_dma_addr)) {
> +		tx_dma_addr = 0;
> +		ret = -ENOMEM;
> +		goto error;
> +	}

The core can do all the DMA mapping for you if you provide a can_dma()
operation, this supports switching between DMA and non-DMA modes per
transfer - often you'll get better performance from PIO for smaller
lengths due to the overhead of setting up DMA and taking the interrupt
on completion.

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