linux-kernel - Re: [PATCH v5 2/2] dma: Add Xilinx AXI Video Direct Memory Access Engine driver support

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Message-ID: <1394822501.28803.280.camel@smile.fi.intel.com>
Date:	Fri, 14 Mar 2014 20:41:41 +0200
From:	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:	Srikanth Thokala <sthokal@...inx.com>
Cc:	dan.j.williams@...el.com, vinod.koul@...el.com,
	michal.simek@...inx.com, grant.likely@...aro.org,
	robh+dt@...nel.org, levex@...ux.com, lars@...afoo.de,
	jaswinder.singh@...aro.org, dmaengine@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 2/2] dma: Add Xilinx AXI Video Direct Memory Access
 Engine driver support

On Fri, 2014-03-14 at 23:20 +0530, Srikanth Thokala wrote:
> This is the driver for the AXI Video Direct Memory Access (AXI
> VDMA) core, which is a soft Xilinx IP core that provides high-
> bandwidth direct memory access between memory and AXI4-Stream
> type video target peripherals. The core provides efficient two
> dimensional DMA operations with independent asynchronous read
> and write channel operation.
> 
> This module works on Zynq (ARM Based SoC) and Microblaze platforms.

Few comments below.

[]

> +++ b/drivers/dma/xilinx/xilinx_vdma.c

[]

> +/**
> + * xilinx_vdma_prep_slave_sg - prepare a descriptor for a DMA_SLAVE transaction
> + * @dchan: DMA channel
> + * @xt: Interleaved template pointer
> + * @flags: transfer ack flags
> + *
> + * Return: Async transaction descriptor on success and NULL on failure
> + */
> +static struct dma_async_tx_descriptor *
> +xilinx_vdma_dma_prep_interleaved(struct dma_chan *dchan,
> +				 struct dma_interleaved_template *xt,
> +				 unsigned long flags)
> +{
> +	struct xilinx_vdma_chan *chan = to_xilinx_chan(dchan);
> +	struct xilinx_vdma_tx_descriptor *desc;
> +	struct xilinx_vdma_tx_segment *segment, *prev = NULL;
> +	struct xilinx_vdma_desc_hw *hw;
> +
> +	if ((xt->dir != DMA_MEM_TO_DEV) && (xt->dir != DMA_DEV_TO_MEM))
> +		return NULL;

!is_slave_direction()

[]

> +static int xilinx_vdma_chan_probe(struct xilinx_vdma_device *xdev,
> +				  struct device_node *node)
> +{
> +	struct xilinx_vdma_chan *chan;
> +	bool has_dre = false;
> +	u32 value, width;
> +	int err;

[]

> +	width = value >> 3; /* Convert bits to bytes */
> +
> +	/* If data width is greater than 8 bytes, DRE is not in hw */
> +	if (width > 8)
> +		has_dre = false;
> +
> +	if (!has_dre)
> +		xdev->common.copy_align = fls(width - 1);

Is width power of two? For me looks like it should be fls(width) - 1;

So, device can't work with alignment less than defined in this case,
correct?

[]

> +/**
> + * xilinx_vdma_probe - Driver probe function
> + * @pdev: Pointer to the platform_device structure
> + *
> + * Return: '0' on success and failure value on error
> + */
> +static int xilinx_vdma_probe(struct platform_device *pdev)
> +{
> +	struct device_node *node = pdev->dev.of_node;
> +	struct xilinx_vdma_device *xdev;
> +	struct device_node *child;
> +	struct resource *io;
> +	u32 num_frames;
> +	int i, err;
> +
> +	dev_info(&pdev->dev, "Probing xilinx axi vdma engine\n");

dev_dbg? Or move this to the end of function and change text to
something like "Probed ..."


-- 
Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Intel Finland Oy

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