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SubjectRe: [PATCH v4 5/7] dmaengine: xilinx_dma: autodetect whether the HW supports scatter-gather
On 02-08-18, 16:10, Andrea Merello wrote:
> The AXIDMA and CDMA HW can be either direct-access or scatter-gather
> version. These are SW incompatible.
>
> The driver can handle both versions: a DT property was used to
> tell the driver whether to assume the HW is in scatter-gather mode.
>
> This patch makes the driver to autodetect this information. The DT
> property is not required anymore.
>
> No changes for VDMA.
>
> Cc: Rob Herring <robh+dt@kernel.org>
> Cc: Mark Rutland <mark.rutland@arm.com>
> Cc: devicetree@vger.kernel.org
> Cc: Radhey Shyam Pandey <radhey.shyam.pandey@xilinx.com>
> Signed-off-by: Andrea Merello <andrea.merello@gmail.com>
> Reviewed-by: Radhey Shyam Pandey <radhey.shyam.pandey@xilinx.com>
> ---
> Changes in v2:
> - autodetect only in !VDMA case
> Changes in v3:
> - cc DT maintainers/ML
> Changes in v4:
> - fix typos in commit message
> ---
> drivers/dma/xilinx/xilinx_dma.c | 14 ++++++++++----

So you are not removing this property from binding document? Or are
there variants which dont have hw mechanism?

> 1 file changed, 10 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/dma/xilinx/xilinx_dma.c b/drivers/dma/xilinx/xilinx_dma.c
> index b17f24e4ec35..78d0f2f8225e 100644
> --- a/drivers/dma/xilinx/xilinx_dma.c
> +++ b/drivers/dma/xilinx/xilinx_dma.c
> @@ -86,6 +86,7 @@
> #define XILINX_DMA_DMASR_DMA_DEC_ERR BIT(6)
> #define XILINX_DMA_DMASR_DMA_SLAVE_ERR BIT(5)
> #define XILINX_DMA_DMASR_DMA_INT_ERR BIT(4)
> +#define XILINX_DMA_DMASR_SG_MASK BIT(3)
> #define XILINX_DMA_DMASR_IDLE BIT(1)
> #define XILINX_DMA_DMASR_HALTED BIT(0)
> #define XILINX_DMA_DMASR_DELAY_MASK GENMASK(31, 24)
> @@ -407,7 +408,6 @@ struct xilinx_dma_config {
> * @dev: Device Structure
> * @common: DMA device structure
> * @chan: Driver specific DMA channel
> - * @has_sg: Specifies whether Scatter-Gather is present or not
> * @mcdma: Specifies whether Multi-Channel is present or not
> * @flush_on_fsync: Flush on frame sync
> * @ext_addr: Indicates 64 bit addressing is supported by dma device
> @@ -427,7 +427,6 @@ struct xilinx_dma_device {
> struct device *dev;
> struct dma_device common;
> struct xilinx_dma_chan *chan[XILINX_DMA_MAX_CHANS_PER_DEVICE];
> - bool has_sg;
> bool mcdma;
> u32 flush_on_fsync;
> bool ext_addr;
> @@ -2400,7 +2399,6 @@ static int xilinx_dma_chan_probe(struct xilinx_dma_device *xdev,
>
> chan->dev = xdev->dev;
> chan->xdev = xdev;
> - chan->has_sg = xdev->has_sg;
> chan->desc_pendingcount = 0x0;
> chan->ext_addr = xdev->ext_addr;
> /* This variable ensures that descriptors are not
> @@ -2493,6 +2491,15 @@ static int xilinx_dma_chan_probe(struct xilinx_dma_device *xdev,
> chan->stop_transfer = xilinx_dma_stop_transfer;
> }
>
> + /* check if SG is enabled (only for AXIDMA and CDMA) */
> + if (xdev->dma_config->dmatype != XDMA_TYPE_VDMA) {
> + if (dma_ctrl_read(chan, XILINX_DMA_REG_DMASR) &
> + XILINX_DMA_DMASR_SG_MASK)
> + chan->has_sg = true;
> + dev_dbg(chan->dev, "ch %d: SG %s\n", chan->id,
> + chan->has_sg ? "enabled" : "disabled");
> + }
> +
> /* Initialize the tasklet */
> tasklet_init(&chan->tasklet, xilinx_dma_do_tasklet,
> (unsigned long)chan);
> @@ -2631,7 +2638,6 @@ static int xilinx_dma_probe(struct platform_device *pdev)
> return PTR_ERR(xdev->regs);
>
> /* Retrieve the DMA engine properties from the device tree */
> - xdev->has_sg = of_property_read_bool(node, "xlnx,include-sg");
> xdev->max_buffer_len = GENMASK(XILINX_DMA_MAX_TRANS_LEN_MAX - 1, 0);
>
> if (xdev->dma_config->dmatype == XDMA_TYPE_AXIDMA) {
> --
> 2.17.1

--
~Vinod

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