Messages in this thread | | | Subject | Re: [PATCH] spi: davinci: Allow device tree devices to use DMA | From | David Lechner <> | Date | Sun, 20 Nov 2016 11:01:02 -0600 |
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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 <david@lechnology.com> >> --- >> 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 >
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