linux-kernel - RE: [PATCH 5/6] dmaengine: xilinx_dma: autodetect whether the HW supports scatter-gather

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Date:   Wed, 20 Jun 2018 14:43:36 +0000
From:   Radhey Shyam Pandey <radheys@...inx.com>
To:     Andrea Merello <andrea.merello@...il.com>,
        "vkoul@...nel.org" <vkoul@...nel.org>,
        "dan.j.williams@...el.com" <dan.j.williams@...el.com>,
        Michal Simek <michals@...inx.com>,
        Appana Durga Kedareswara Rao <appanad@...inx.com>,
        "dmaengine@...r.kernel.org" <dmaengine@...r.kernel.org>
CC:     "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH 5/6] dmaengine: xilinx_dma: autodetect whether the HW
 supports scatter-gather

> -----Original Message-----
> From: dmaengine-owner@...r.kernel.org [mailto:dmaengine-
> owner@...r.kernel.org] On Behalf Of Andrea Merello
> Sent: Wednesday, June 20, 2018 2:07 PM
> To: vkoul@...nel.org; dan.j.williams@...el.com; Michal Simek
> <michals@...inx.com>; Appana Durga Kedareswara Rao
> <appanad@...inx.com>; dmaengine@...r.kernel.org
> Cc: linux-arm-kernel@...ts.infradead.org; linux-kernel@...r.kernel.org;
> Andrea Merello <andrea.merello@...il.com>
> Subject: [PATCH 5/6] dmaengine: xilinx_dma: autodetect whether the HW
> supports scatter-gather
> 
> The HW can be either direct-access or scatter-gather version. These are
> SW incompatible.
> 
> The driver can handle both version: a DT property was used to
> tell the driver whether to assume the HW is is scatter-gather mode.
> 
> This patch makes the driver to autodetect this information. The DT
> property is not required anymore.
> 
> Signed-off-by: Andrea Merello <andrea.merello@...il.com>
> ---
>  drivers/dma/xilinx/xilinx_dma.c | 12 ++++++++----
>  1 file changed, 8 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/dma/xilinx/xilinx_dma.c b/drivers/dma/xilinx/xilinx_dma.c
> index bdbc8ba9092a..8c6e818e596f 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
> @@ -426,7 +426,6 @@ 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;
> @@ -2391,7 +2390,6 @@ 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
> @@ -2488,6 +2486,13 @@ static int xilinx_dma_chan_probe(struct
> xilinx_dma_device *xdev,
>  		chan->stop_transfer = xilinx_dma_stop_transfer;
>  	}
> 
> +	/* check if SG is enabled */
> +	if (dma_ctrl_read(chan, XILINX_DMA_REG_DMASR) &
> +		XILINX_DMA_DMASR_SG_MASK)
I think SGIncld mask is only applicable for AXI DMA and CDMA IP.
For VDMA IP this bit is reserved. 
.
> +		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);
> @@ -2626,7 +2631,6 @@ static int xilinx_dma_probe(struct platform_device
> *pdev)
>  		return PTR_ERR(xdev->regs);
> 
>  	/* Retrieve the DMA engine properties from the device tree */
> -
Unrelated change

>  	if (xdev->dma_config->dmatype == XDMA_TYPE_AXIDMA) {
>  		xdev->mcdma = of_property_read_bool(node, "xlnx,mcdma");
>  		err = of_property_read_u32(node, "xlnx,lengthregwidth",
> --
> 2.17.1
> 
> --
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