Re: [PATCH v4] dma: Add Xilinx AXI Direct Memory Access Engine driver support

[Mark Rutland <mark.rutland@arm.com>]

Hi,

On Wed, Oct 15, 2014 at 01:00:36PM +0100, Srikanth Thokala wrote:
> This is the driver for the AXI Direct Memory Access (AXI DMA)
> core, which is a soft Xilinx IP core that provides high-
> bandwidth direct memory access between memory and AXI4-Stream
> type target peripherals.
> 
> This module works on Zynq (ARM Based SoC) and Microblaze platforms.
> 
> Signed-off-by: Srikanth Thokala <sthokal@xilinx.com>
> ---
> Changes in v4:
> - Add direction field to VDMA descriptor structure and removed from
>   channel structure to avoid duplication.
> - Check for DMA idle condition before changing the configuration.
> - Residue is being calculated in complete_descriptor() and is reported
>   to slave driver.
> 
> Changes in v3:
> - Rebased on 3.16-rc7
> 
> Changes in v2:
> - Simplified the logic to set SOP and APP words in prep_slave_sg().
> - Corrected function description comments to match the return type.
> - Fixed some minor comments as suggested by Andy, Thanks.
> ---
>  drivers/dma/Kconfig             |   13 +
>  drivers/dma/xilinx/Makefile     |    1 +
>  drivers/dma/xilinx/xilinx_dma.c | 1242 +++++++++++++++++++++++++++++++++++++++
>  include/linux/amba/xilinx_dma.h |   17 +
>  4 files changed, 1273 insertions(+)
>  create mode 100644 drivers/dma/xilinx/xilinx_dma.c

[...]

> +static int xilinx_dma_chan_probe(struct xilinx_dma_device *xdev,
> +                                struct device_node *node)
> +{
> +       struct xilinx_dma_chan *chan;
> +       int err;
> +       bool has_dre;
> +       u32 value, width = 0;
> +
> +       /* Allocate a channel */
> +       chan = devm_kzalloc(xdev->dev, sizeof(*chan), GFP_KERNEL);
> +       if (!chan)
> +               return -ENOMEM;
> +
> +       chan->dev = xdev->dev;
> +       chan->xdev = xdev;
> +       chan->has_sg = xdev->has_sg;
> +
> +       spin_lock_init(&chan->lock);
> +       INIT_LIST_HEAD(&chan->pending_list);
> +       INIT_LIST_HEAD(&chan->done_list);
> +       INIT_LIST_HEAD(&chan->free_seg_list);
> +
> +       /* Get the DT properties */
> +       has_dre = of_property_read_bool(node, "xlnx,include-dre");
> +
> +       err = of_property_read_u32(node, "xlnx,datawidth", &value);
> +       if (err) {
> +               dev_err(xdev->dev, "unable to read datawidth property");
> +               return 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);
> +
> +       if (of_device_is_compatible(node, "xlnx,axi-dma-mm2s-channel")) {
> +               chan->id = 0;
> +               chan->ctrl_offset = XILINX_DMA_MM2S_CTRL_OFFSET;
> +       } else if (of_device_is_compatible(node,
> +                                          "xlnx,axi-dma-s2mm-channel")) {
> +               chan->id = 1;
> +               chan->ctrl_offset = XILINX_DMA_S2MM_CTRL_OFFSET;
> +       } else {
> +               dev_err(xdev->dev, "Invalid channel compatible node\n");
> +               return -EINVAL;
> +       }
> +
> +       /* Find the IRQ line, if it exists in the device tree */
> +       chan->irq = irq_of_parse_and_map(node, 0);
> +       err = request_irq(chan->irq, xilinx_dma_irq_handler,
> +                         IRQF_SHARED,
> +                         "xilinx-dma-controller", chan);
> +       if (err) {
> +               dev_err(xdev->dev, "unable to request IRQ %d\n", chan->irq);
> +               return err;
> +       }
> +
> +       /* Initialize the tasklet */
> +       tasklet_init(&chan->tasklet, xilinx_dma_do_tasklet,
> +                    (unsigned long)chan);
> +
> +       /*
> +        * Initialize the DMA channel and add it to the DMA engine channels
> +        * list.
> +        */
> +       chan->common.device = &xdev->common;
> +
> +       list_add_tail(&chan->common.device_node, &xdev->common.channels);
> +       xdev->chan[chan->id] = chan;
> +
> +       /* Reset the channel */
> +       err = xilinx_dma_reset(chan);
> +       if (err) {
> +               dev_err(xdev->dev, "Reset channel failed\n");
> +               return err;
> +       }
> +
> +       return 0;
> +}
> +
> +/**
> + * of_dma_xilinx_xlate - Translation function
> + * @dma_spec: Pointer to DMA specifier as found in the device tree
> + * @ofdma: Pointer to DMA controller data
> + *
> + * Return: DMA channel pointer on success and NULL on error
> + */
> +static struct dma_chan *of_dma_xilinx_xlate(struct of_phandle_args *dma_spec,
> +                                           struct of_dma *ofdma)
> +{
> +       struct xilinx_dma_device *xdev = ofdma->of_dma_data;
> +       int chan_id = dma_spec->args[0];
> +
> +       if (chan_id >= XILINX_DMA_MAX_CHANS_PER_DEVICE)
> +               return NULL;
> +
> +       return dma_get_slave_channel(&xdev->chan[chan_id]->common);
> +}
> +
> +/**
> + * xilinx_dma_probe - Driver probe function
> + * @pdev: Pointer to the platform_device structure
> + *
> + * Return: '0' on success and failure value on error
> + */
> +static int xilinx_dma_probe(struct platform_device *pdev)
> +{
> +       struct xilinx_dma_device *xdev;
> +       struct device_node *child, *node;
> +       struct resource *res;
> +       int i, ret;
> +
> +       xdev = devm_kzalloc(&pdev->dev, sizeof(*xdev), GFP_KERNEL);
> +       if (!xdev)
> +               return -ENOMEM;
> +
> +       xdev->dev = &(pdev->dev);
> +       INIT_LIST_HEAD(&xdev->common.channels);
> +
> +       node = pdev->dev.of_node;
> +
> +       /* Map the registers */
> +       res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> +       xdev->regs = devm_ioremap_resource(&pdev->dev, res);
> +       if (IS_ERR(xdev->regs))
> +               return PTR_ERR(xdev->regs);
> +
> +       /* Check if SG is enabled */
> +       xdev->has_sg = of_property_read_bool(node, "xlnx,include-sg");
> +
> +       /* Axi DMA only do slave transfers */
> +       dma_cap_set(DMA_SLAVE, xdev->common.cap_mask);
> +       dma_cap_set(DMA_PRIVATE, xdev->common.cap_mask);
> +       xdev->common.device_prep_slave_sg = xilinx_dma_prep_slave_sg;
> +       xdev->common.device_control = xilinx_dma_device_control;
> +       xdev->common.device_issue_pending = xilinx_dma_issue_pending;
> +       xdev->common.device_alloc_chan_resources =
> +               xilinx_dma_alloc_chan_resources;
> +       xdev->common.device_free_chan_resources =
> +               xilinx_dma_free_chan_resources;
> +       xdev->common.device_tx_status = xilinx_dma_tx_status;
> +       xdev->common.device_slave_caps = xilinx_dma_device_slave_caps;
> +       xdev->common.dev = &pdev->dev;
> +
> +       platform_set_drvdata(pdev, xdev);
> +
> +       for_each_child_of_node(node, child) {
> +               ret = xilinx_dma_chan_probe(xdev, child);
> +               if (ret) {
> +                       dev_err(&pdev->dev, "Probing channels failed\n");
> +                       goto free_chan_resources;
> +               }
> +       }
> +
> +       dma_async_device_register(&xdev->common);
> +
> +       ret = of_dma_controller_register(node, of_dma_xilinx_xlate, xdev);
> +       if (ret) {
> +               dev_err(&pdev->dev, "Unable to register DMA to DT\n");
> +               dma_async_device_unregister(&xdev->common);
> +               goto free_chan_resources;
> +       }
> +
> +       dev_info(&pdev->dev, "Xilinx AXI DMA Engine driver Probed!!\n");
> +
> +       return 0;
> +
> +free_chan_resources:
> +       for (i = 0; i < XILINX_DMA_MAX_CHANS_PER_DEVICE; i++)
> +               if (xdev->chan[i])
> +                       xilinx_dma_chan_remove(xdev->chan[i]);
> +
> +       return ret;
> +}
> +
> +/**
> + * xilinx_dma_remove - Driver remove function
> + * @pdev: Pointer to the platform_device structure
> + *
> + * Return: Always '0'
> + */
> +static int xilinx_dma_remove(struct platform_device *pdev)
> +{
> +       struct xilinx_dma_device *xdev = platform_get_drvdata(pdev);
> +       int i;
> +
> +       of_dma_controller_free(pdev->dev.of_node);
> +       dma_async_device_unregister(&xdev->common);
> +
> +       for (i = 0; i < XILINX_DMA_MAX_CHANS_PER_DEVICE; i++)
> +               if (xdev->chan[i])
> +                       xilinx_dma_chan_remove(xdev->chan[i]);
> +
> +       return 0;
> +}
> +
> +static const struct of_device_id xilinx_dma_of_match[] = {
> +       { .compatible = "xlnx,axi-dma-1.00.a",},
> +       {}
> +};
> +MODULE_DEVICE_TABLE(of, xilinx_dma_of_match);

This patch has come without the necessary device tree binding document,
and I was not able to find an existing binding document upstream (I
searched for "xlnx,axi-dma-1.00.a" and "axi-dma").

The driver expects a non-trivial set of properties, so a binding
document is essential for users. Additionally, checkpatch.pl should
scream regarding the undocumented comaptible string.

Please put together a binding document.

Thanks,
Mark.