From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753099AbcKTRBI (ORCPT ); Sun, 20 Nov 2016 12:01:08 -0500 Received: from vern.gendns.com ([206.190.152.46]:55141 "EHLO vern.gendns.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751544AbcKTRBF (ORCPT ); Sun, 20 Nov 2016 12:01:05 -0500 Subject: Re: [PATCH] spi: davinci: Allow device tree devices to use DMA To: Sekhar Nori , Mark Brown References: <1479530464-12538-1-git-send-email-david@lechnology.com> <79f186b5-ac71-189f-c19f-977670395043@ti.com> Cc: khilman@kernel.org, linux-spi@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org From: David Lechner Message-ID: <946d60bc-ac14-7934-c1b3-e2de03831459@lechnology.com> Date: Sun, 20 Nov 2016 11:01:02 -0600 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.3.0 MIME-Version: 1.0 In-Reply-To: <79f186b5-ac71-189f-c19f-977670395043@ti.com> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit X-AntiAbuse: This header was added to track abuse, please include it with any abuse report X-AntiAbuse: Primary Hostname - vern.gendns.com X-AntiAbuse: Original Domain - vger.kernel.org X-AntiAbuse: Originator/Caller UID/GID - [47 12] / [47 12] X-AntiAbuse: Sender Address Domain - lechnology.com X-Get-Message-Sender-Via: vern.gendns.com: authenticated_id: davidmain+lechnology.com/only user confirmed/virtual account not confirmed X-Authenticated-Sender: vern.gendns.com: davidmain@lechnology.com X-Source: X-Source-Args: X-Source-Dir: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 11/20/2016 06:59 AM, Sekhar Nori wrote: > On Saturday 19 November 2016 10:11 AM, David Lechner wrote: >> This makes SPI devices specified in a device tree use DMA when the master >> controller has DMA configured. >> >> Since device tree is supposed to only describe the hardware, adding a >> configuration option to device tree to enable DMA per-device would not be >> acceptable. So, this is the best we can do for now to get SPI devices >> working with DMA when using device tree. >> >> Unfortunately, this excludes the possibility of using one SPI device with >> DMA and one without on the same master. >> >> I have tested this on LEGO MINDSTORMS EV3 using the NOR flash. Reading the >> flash memory would fail with -EIO when DMA is not enabled for the device. >> >> Signed-off-by: David Lechner >> --- >> drivers/spi/spi-davinci.c | 4 ++++ >> 1 file changed, 4 insertions(+) >> >> diff --git a/drivers/spi/spi-davinci.c b/drivers/spi/spi-davinci.c >> index d36c11b..c6cf73a 100644 >> --- a/drivers/spi/spi-davinci.c >> +++ b/drivers/spi/spi-davinci.c >> @@ -388,6 +388,7 @@ static int davinci_spi_setup_transfer(struct spi_device *spi, >> static int davinci_spi_of_setup(struct spi_device *spi) >> { >> struct davinci_spi_config *spicfg = spi->controller_data; >> + struct davinci_spi *dspi = spi_master_get_devdata(spi->master); >> struct device_node *np = spi->dev.of_node; >> u32 prop; >> >> @@ -400,6 +401,9 @@ static int davinci_spi_of_setup(struct spi_device *spi) >> if (!of_property_read_u32(np, "ti,spi-wdelay", &prop)) >> spicfg->wdelay = (u8)prop; >> spi->controller_data = spicfg; >> + /* Use DMA for device if master supports it */ >> + if (dspi->dma_rx) > > This should be > > if (!(IS_ERR(dpsi->dma_rx) || IS_ERR(dspi->dma_tx)) There is the following code in davinci_spi_probe(): ret = davinci_spi_request_dma(dspi); if (ret == -EPROBE_DEFER) { goto free_clk; } else if (ret) { dev_info(&pdev->dev, "DMA is not supported (%d)\n", ret); dspi->dma_rx = NULL; dspi->dma_tx = NULL; } So, I does not look like it is possible to get anything other than NULL or a valid pointer for dpsi->dma_rx and that checking dpsi->dma_tx is not necessary. So, I think if (dspi->dma_rx) is sufficient. In fact the same check is used during unwinding if the probe function fails. > >> + spicfg->io_type = SPI_IO_TYPE_DMA; > > Otherwise looks good to me. > > Thanks, > Sekhar >