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[2/4] spi: spi-fsl-dspi: Fix incorrect DMA setup

Message ID d83f4896d77f577ca92fd70534f6198bb3288d8a.1479384571.git.maitysanchayan@gmail.com (mailing list archive)
State New, archived
Headers show

Commit Message

Sanchayan Nov. 17, 2016, 12:16 p.m. UTC
Currently dmaengine_prep_slave_single was being called with length
set to the complete DMA buffer size. This resulted in unwanted bytes
being transferred to the SPI register leading to clock and MOSI lines
having unwanted data even after chip select got deasserted and the
required bytes having been transferred.

Signed-off-by: Sanchayan Maity <maitysanchayan@gmail.com>
---
 drivers/spi/spi-fsl-dspi.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

Comments

Stefan Agner Nov. 18, 2016, 1:03 a.m. UTC | #1
On 2016-11-17 04:16, Sanchayan Maity wrote:
> Currently dmaengine_prep_slave_single was being called with length
> set to the complete DMA buffer size. This resulted in unwanted bytes
> being transferred to the SPI register leading to clock and MOSI lines
> having unwanted data even after chip select got deasserted and the
> required bytes having been transferred.
> 
> Signed-off-by: Sanchayan Maity <maitysanchayan@gmail.com>
> ---
>  drivers/spi/spi-fsl-dspi.c | 10 ++++++++--
>  1 file changed, 8 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/spi/spi-fsl-dspi.c b/drivers/spi/spi-fsl-dspi.c
> index b1ee1f5..aee8c88 100644
> --- a/drivers/spi/spi-fsl-dspi.c
> +++ b/drivers/spi/spi-fsl-dspi.c
> @@ -265,7 +265,10 @@ static int dspi_next_xfer_dma_submit(struct fsl_dspi *dspi)
>  
>  	dma->tx_desc = dmaengine_prep_slave_single(dma->chan_tx,
>  					dma->tx_dma_phys,
> -					DSPI_DMA_BUFSIZE, DMA_MEM_TO_DEV,
> +					dma->curr_xfer_len *
> +					DMA_SLAVE_BUSWIDTH_4_BYTES /
> +					(tx_word ? 2 : 1),
> +					DMA_MEM_TO_DEV,

Hm, this is getting ridiculous, I think we convert curr_xfer_len from
bytes to DMA transfers in almost every use.

Can we make it be transfer length in actual 4 byte transfers? We then
probably have to convert it to bytes once to subtract from
curr_remaining_bytes, but I think it would simplify code overall...

--
Stefan


>  					DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
>  	if (!dma->tx_desc) {
>  		dev_err(dev, "Not able to get desc for DMA xfer\n");
> @@ -281,7 +284,10 @@ static int dspi_next_xfer_dma_submit(struct fsl_dspi *dspi)
>  
>  	dma->rx_desc = dmaengine_prep_slave_single(dma->chan_rx,
>  					dma->rx_dma_phys,
> -					DSPI_DMA_BUFSIZE, DMA_DEV_TO_MEM,
> +					dma->curr_xfer_len *
> +					DMA_SLAVE_BUSWIDTH_4_BYTES /
> +					(tx_word ? 2 : 1),
> +					DMA_DEV_TO_MEM,
>  					DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
>  	if (!dma->rx_desc) {
>  		dev_err(dev, "Not able to get desc for DMA xfer\n");
diff mbox

Patch

diff --git a/drivers/spi/spi-fsl-dspi.c b/drivers/spi/spi-fsl-dspi.c
index b1ee1f5..aee8c88 100644
--- a/drivers/spi/spi-fsl-dspi.c
+++ b/drivers/spi/spi-fsl-dspi.c
@@ -265,7 +265,10 @@  static int dspi_next_xfer_dma_submit(struct fsl_dspi *dspi)
 
 	dma->tx_desc = dmaengine_prep_slave_single(dma->chan_tx,
 					dma->tx_dma_phys,
-					DSPI_DMA_BUFSIZE, DMA_MEM_TO_DEV,
+					dma->curr_xfer_len *
+					DMA_SLAVE_BUSWIDTH_4_BYTES /
+					(tx_word ? 2 : 1),
+					DMA_MEM_TO_DEV,
 					DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
 	if (!dma->tx_desc) {
 		dev_err(dev, "Not able to get desc for DMA xfer\n");
@@ -281,7 +284,10 @@  static int dspi_next_xfer_dma_submit(struct fsl_dspi *dspi)
 
 	dma->rx_desc = dmaengine_prep_slave_single(dma->chan_rx,
 					dma->rx_dma_phys,
-					DSPI_DMA_BUFSIZE, DMA_DEV_TO_MEM,
+					dma->curr_xfer_len *
+					DMA_SLAVE_BUSWIDTH_4_BYTES /
+					(tx_word ? 2 : 1),
+					DMA_DEV_TO_MEM,
 					DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
 	if (!dma->rx_desc) {
 		dev_err(dev, "Not able to get desc for DMA xfer\n");