[PATCH v2 1/2] spi: rspi: Handle dmaengine_prep_slave_sg() failures gracefully

[PATCH v2 1/2] spi: rspi: Handle dmaengine_prep_slave_sg() failures gracefully

[Geert Uytterhoeven]

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: Geert Uytterhoeven <geert+renesas@glider.be>
Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
---
v2:
  - Add Acked-by
---
 drivers/spi/spi-rspi.c | 30 ++++++++++++++++++++++--------
 1 file changed, 22 insertions(+), 8 deletions(-)

diff --git a/drivers/spi/spi-rspi.c b/drivers/spi/spi-rspi.c
index 38fd938d6360..c850dfdfa9e3 100644
--- a/drivers/spi/spi-rspi.c
+++ b/drivers/spi/spi-rspi.c
@@ -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,
-					 xfer->rx_buf ? &xfer->rx_sg : NULL);
+		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);
 }
-- 
1.9.1

[PATCH v2 2/2] spi: sh-msiof: Handle dmaengine_prep_slave_single() failures gracefully

[Geert Uytterhoeven]

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: Geert Uytterhoeven <geert+renesas@glider.be>
Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
---
v2:
  - Add Acked-by
---
 drivers/spi/spi-sh-msiof.c | 23 +++++++++++++++--------
 1 file changed, 15 insertions(+), 8 deletions(-)

diff --git a/drivers/spi/spi-sh-msiof.c b/drivers/spi/spi-sh-msiof.c
index 6f449b24704a..2a4354dcd661 100644
--- a/drivers/spi/spi-sh-msiof.c
+++ b/drivers/spi/spi-sh-msiof.c
@@ -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->master->dma_tx->device->dev,
@@ -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);
@@ -823,6 +824,12 @@ 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;
 
-- 
1.9.1

Re: [PATCH v2 1/2] spi: rspi: Handle dmaengine_prep_slave_sg() failures gracefully

[Mark Brown]

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On Fri, Jul 11, 2014 at 06:01:16PM +0200, Geert Uytterhoeven wrote:

> Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
> Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> ---
> v2:
>   - Add Acked-by

Please don't ever resend things to add Acked-by - this just adds to
noise and mail volume.

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