Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752253AbcKRINC (ORCPT ); Fri, 18 Nov 2016 03:13:02 -0500 Received: from mail-pf0-f194.google.com ([209.85.192.194]:35612 "EHLO mail-pf0-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751180AbcKRINA (ORCPT ); Fri, 18 Nov 2016 03:13:00 -0500 Date: Fri, 18 Nov 2016 13:34:03 +0530 From: maitysanchayan@gmail.com To: Stefan Agner Cc: broonie@kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-spi@vger.kernel.org Subject: Re: [PATCH 2/4] spi: spi-fsl-dspi: Fix incorrect DMA setup Message-ID: <20161118080403.GB1572@Sanchayan-Arch.localdomain> References: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.7.1 (2016-10-04) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 6425 Lines: 154 On 16-11-17 17:03:19, Stefan Agner wrote: > 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 > > --- > > 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... Will the below be acceptable fix? diff --git a/drivers/spi/spi-fsl-dspi.c b/drivers/spi/spi-fsl-dspi.c index 41422cd..db7f091 100644 --- a/drivers/spi/spi-fsl-dspi.c +++ b/drivers/spi/spi-fsl-dspi.c @@ -217,15 +217,13 @@ static void dspi_rx_dma_callback(void *arg) struct fsl_dspi *dspi = arg; struct fsl_dspi_dma *dma = dspi->dma; int rx_word; - int i, len; + int i; u16 d; rx_word = is_double_byte_mode(dspi); - len = rx_word ? (dma->curr_xfer_len / 2) : dma->curr_xfer_len; - if (!(dspi->dataflags & TRAN_STATE_RX_VOID)) { - for (i = 0; i < len; i++) { + for (i = 0; i < dma->curr_xfer_len; i++) { d = dspi->dma->rx_dma_buf[i]; rx_word ? (*(u16 *)dspi->rx = d) : (*(u8 *)dspi->rx = d); @@ -242,14 +240,12 @@ static int dspi_next_xfer_dma_submit(struct fsl_dspi *dspi) struct device *dev = &dspi->pdev->dev; int time_left; int tx_word; - int i, len; + int i; u16 val; tx_word = is_double_byte_mode(dspi); - len = tx_word ? (dma->curr_xfer_len / 2) : dma->curr_xfer_len; - - for (i = 0; i < len - 1; i++) { + for (i = 0; i < dma->curr_xfer_len - 1; i++) { val = tx_word ? *(u16 *) dspi->tx : *(u8 *) dspi->tx; dspi->dma->tx_dma_buf[i] = SPI_PUSHR_TXDATA(val) | SPI_PUSHR_PCS(dspi->cs) | @@ -267,7 +263,9 @@ 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, + 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"); @@ -283,7 +281,9 @@ 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, + 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"); @@ -330,17 +330,17 @@ static int dspi_dma_xfer(struct fsl_dspi *dspi) struct device *dev = &dspi->pdev->dev; int curr_remaining_bytes; int bytes_per_buffer; - int tx_word; + int tx_word = 1; int ret = 0; - tx_word = is_double_byte_mode(dspi); + if (is_double_byte_mode(dspi)) + tx_word = 2; curr_remaining_bytes = dspi->len; + bytes_per_buffer = DSPI_DMA_BUFSIZE / DSPI_FIFO_SIZE; while (curr_remaining_bytes) { /* Check if current transfer fits the DMA buffer */ - dma->curr_xfer_len = curr_remaining_bytes; - bytes_per_buffer = DSPI_DMA_BUFSIZE / - (DSPI_FIFO_SIZE / (tx_word ? 2 : 1)); - if (curr_remaining_bytes > bytes_per_buffer) + dma->curr_xfer_len = curr_remaining_bytes / tx_word; + if (dma->curr_xfer_len > bytes_per_buffer) dma->curr_xfer_len = bytes_per_buffer; ret = dspi_next_xfer_dma_submit(dspi); @@ -349,7 +349,7 @@ static int dspi_dma_xfer(struct fsl_dspi *dspi) goto exit; } else { - curr_remaining_bytes -= dma->curr_xfer_len; + curr_remaining_bytes -= dma->curr_xfer_len * tx_word; if (curr_remaining_bytes < 0) curr_remaining_bytes = 0; dspi->len = curr_remaining_bytes; Regards, Sanchayan. > > -- > 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");