Re: [PATCH] spi: omap2-mcspi: handle DMA setup failures

[Mark Brown]

On Tue, Oct 13, 2026 at 07:50:04PM +0530, Sahaj Chaudhari wrote:
> The DMA paths ignore failures from dmaengine_slave_config(), descriptor
> preparation and dmaengine_submit(), and carry FIXME comments about
> falling back to PIO. A failed setup can leave a half-started transfer
> or wait for a completion that never arrives.

> @@ -1227,10 +1300,27 @@ static int omap2_mcspi_transfer_one(struct spi_controller *ctlr,
>  					+ OMAP2_MCSPI_TX0);
>  
>  		if ((mcspi_dma->dma_rx && mcspi_dma->dma_tx) &&
> -		    spi_xfer_is_dma_mapped(ctlr, spi, t))
> -			count = omap2_mcspi_txrx_dma(spi, t);
> -		else
> +		    spi_xfer_is_dma_mapped(ctlr, spi, t)) {
> +			ret = omap2_mcspi_txrx_dma(spi, t, &count,
> +						   &pio_fallback);
> +			if (ret) {
> +				bool is_target = spi_controller_is_target(ctlr);
> +				bool fallback;
> +
> +				fallback = omap2_mcspi_can_pio_fallback(pio_fallback, t,
> +									is_target);
> +				if (!fallback) {
> +					status = ret;
> +					goto out;
> +				}
> +
> +				dev_warn(&spi->dev,
> +					 "DMA setup failed, falling back to PIO\n");
> +				count = omap2_mcspi_txrx_pio(spi, t);

Do we need to turn off the FIFO here before doing PIO?  

> +			}
> +		} else {
>  			count = omap2_mcspi_txrx_pio(spi, t);
> +		}
>  
>  		if (count != t->len) {
>  			status = -EIO;
> @@ -1246,8 +1336,12 @@ static int omap2_mcspi_transfer_one(struct spi_controller *ctlr,
>  out:
>  	/* Restore defaults if they were overriden */
>  	if (par_override) {
> +		int restore_status;
> +
>  		par_override = 0;
> -		status = omap2_mcspi_setup_transfer(spi, NULL);
> +		restore_status = omap2_mcspi_setup_transfer(spi, NULL);
> +		if (!status)
> +			status = restore_status;
>  	}
>  
>  	omap2_mcspi_set_enable(spi, 0);
> -- 
> 2.43.0
>

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