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Commit 85912a88 authored by Geert Uytterhoeven's avatar Geert Uytterhoeven Committed by Mark Brown
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spi: rspi: Handle dmaengine_prep_slave_sg() failures gracefully 



As typically a shmobile SoC has less DMA channels than devices that can use
DMA, we may want to prioritize access to the DMA channels in the future.
This means that dmaengine_prep_slave_sg() may start failing arbitrarily.

Handle dmaengine_prep_slave_sg() failures gracefully by falling back to
PIO.

Signed-off-by: default avatarGeert Uytterhoeven <geert+renesas@glider.be>
Acked-by: default avatarLaurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: default avatarMark Brown <broonie@linaro.org>
parent 533465a8

drivers/spi/spi-rspi.c

+22 −8
Original line number Diff line number Diff line
@@ -477,7 +477,7 @@ static int rspi_dma_transfer(struct rspi_data *rspi, struct sg_table *tx, 
					tx->sgl, tx->nents, DMA_TO_DEVICE,

					DMA_PREP_INTERRUPT | DMA_CTRL_ACK);

		if (!desc_tx)

			return -EIO;

			goto no_dma;



		irq_mask |= SPCR_SPTIE;

	}
@@ -486,7 +486,7 @@ static int rspi_dma_transfer(struct rspi_data *rspi, struct sg_table *tx, 
					rx->sgl, rx->nents, DMA_FROM_DEVICE,

					DMA_PREP_INTERRUPT | DMA_CTRL_ACK);

		if (!desc_rx)

			return -EIO;

			goto no_dma;



		irq_mask |= SPCR_SPRIE;

	}
@@ -540,6 +540,12 @@ static int rspi_dma_transfer(struct rspi_data *rspi, struct sg_table *tx, 
		enable_irq(rspi->rx_irq);



	return ret;



no_dma:

	pr_warn_once("%s %s: DMA not available, falling back to PIO\n",

		     dev_driver_string(&rspi->master->dev),

		     dev_name(&rspi->master->dev));

	return -EAGAIN;

}



static void rspi_receive_init(const struct rspi_data *rspi)
@@ -593,8 +599,10 @@ static int rspi_common_transfer(struct rspi_data *rspi, 


	if (rspi->master->can_dma && __rspi_can_dma(rspi, xfer)) {

		/* rx_buf can be NULL on RSPI on SH in TX-only Mode */

		return rspi_dma_transfer(rspi, &xfer->tx_sg,

		ret = rspi_dma_transfer(rspi, &xfer->tx_sg,

					xfer->rx_buf ? &xfer->rx_sg : NULL);

		if (ret != -EAGAIN)

			return ret;

	}



	ret = rspi_pio_transfer(rspi, xfer->tx_buf, xfer->rx_buf, xfer->len);
@@ -648,8 +656,11 @@ static int qspi_transfer_out(struct rspi_data *rspi, struct spi_transfer *xfer) 
{

	int ret;



	if (rspi->master->can_dma && __rspi_can_dma(rspi, xfer))

		return rspi_dma_transfer(rspi, &xfer->tx_sg, NULL);

	if (rspi->master->can_dma && __rspi_can_dma(rspi, xfer)) {

		ret = rspi_dma_transfer(rspi, &xfer->tx_sg, NULL);

		if (ret != -EAGAIN)

			return ret;

	}



	ret = rspi_pio_transfer(rspi, xfer->tx_buf, NULL, xfer->len);

	if (ret < 0)
@@ -663,8 +674,11 @@ static int qspi_transfer_out(struct rspi_data *rspi, struct spi_transfer *xfer) 


static int qspi_transfer_in(struct rspi_data *rspi, struct spi_transfer *xfer)

{

	if (rspi->master->can_dma && __rspi_can_dma(rspi, xfer))

		return rspi_dma_transfer(rspi, NULL, &xfer->rx_sg);

	if (rspi->master->can_dma && __rspi_can_dma(rspi, xfer)) {

		int ret = rspi_dma_transfer(rspi, NULL, &xfer->rx_sg);

		if (ret != -EAGAIN)

			return ret;

	}



	return rspi_pio_transfer(rspi, NULL, xfer->rx_buf, xfer->len);

}