Commit 279d2378 authored by Geert Uytterhoeven's avatar Geert Uytterhoeven Committed by Mark Brown
Browse files

spi: sh-msiof: Handle dmaengine_prep_slave_single() 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_single() may start failing
arbitrarily.

Handle dmaengine_prep_slave_single() failures gracefully by falling back to
PIO. This requires moving DMA-specific configuration of the MSIOF device
after the call(s) to dmaengine_prep_slave_single().

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 51fd5090

drivers/spi/spi-sh-msiof.c

+15 −8
Original line number Diff line number Diff line
@@ -636,12 +636,6 @@ static int sh_msiof_dma_once(struct sh_msiof_spi_priv *p, const void *tx, 
	dma_cookie_t cookie;

	int ret;



	/* 1 stage FIFO watermarks for DMA */

	sh_msiof_write(p, FCTR, FCTR_TFWM_1 | FCTR_RFWM_1);



	/* setup msiof transfer mode registers (32-bit words) */

	sh_msiof_spi_set_mode_regs(p, tx, rx, 32, len / 4);



	if (tx) {

		ier_bits |= IER_TDREQE | IER_TDMAE;

		dma_sync_single_for_device(&p->pdev->dev, p->tx_dma_addr, len,
@@ -650,7 +644,7 @@ static int sh_msiof_dma_once(struct sh_msiof_spi_priv *p, const void *tx, 
					p->tx_dma_addr, len, DMA_TO_DEVICE,

					DMA_PREP_INTERRUPT | DMA_CTRL_ACK);

		if (!desc_tx)

			return -EIO;

			return -EAGAIN;

	}



	if (rx) {
@@ -659,8 +653,15 @@ static int sh_msiof_dma_once(struct sh_msiof_spi_priv *p, const void *tx, 
					p->rx_dma_addr, len, DMA_FROM_DEVICE,

					DMA_PREP_INTERRUPT | DMA_CTRL_ACK);

		if (!desc_rx)

			return -EIO;

			return -EAGAIN;

	}



	/* 1 stage FIFO watermarks for DMA */

	sh_msiof_write(p, FCTR, FCTR_TFWM_1 | FCTR_RFWM_1);



	/* setup msiof transfer mode registers (32-bit words) */

	sh_msiof_spi_set_mode_regs(p, tx, rx, 32, len / 4);



	sh_msiof_write(p, IER, ier_bits);



	reinit_completion(&p->done);
@@ -822,6 +823,12 @@ static int sh_msiof_transfer_one(struct spi_master *master, 
			copy32(p->tx_dma_page, tx_buf, l / 4);



		ret = sh_msiof_dma_once(p, tx_buf, rx_buf, l);

		if (ret == -EAGAIN) {

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

				     dev_driver_string(&p->pdev->dev),

				     dev_name(&p->pdev->dev));

			break;

		}

		if (ret)

			return ret;

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