Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752247AbcKRBJj (ORCPT ); Thu, 17 Nov 2016 20:09:39 -0500 Received: from mail.kmu-office.ch ([178.209.48.109]:40745 "EHLO mail.kmu-office.ch" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750794AbcKRBJh (ORCPT ); Thu, 17 Nov 2016 20:09:37 -0500 MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Date: Thu, 17 Nov 2016 17:03:19 -0800 From: Stefan Agner To: Sanchayan Maity 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 In-Reply-To: References: Message-ID: User-Agent: Roundcube Webmail/1.1.3 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1955 Lines: 52 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... -- 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");