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SubjectRe: [PATCH V5 XDMA 1/2] dmaengine: xilinx: xdma: Add xilinx xdma driver
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On 10/4/22 01:18, Ilpo Järvinen wrote:
> On Wed, 28 Sep 2022, Lizhi Hou wrote:
>
>> Add driver to enable PCIe board which uses XDMA (the DMA/Bridge Subsystem
>> for PCI Express). For example, Xilinx Alveo PCIe devices.
>> https://www.xilinx.com/products/boards-and-kits/alveo.html
>>
>> The XDMA engine support up to 4 Host to Card (H2C) and 4 Card to Host (C2H)
>> channels. Memory transfers are specified on a per-channel basis in
>> descriptor linked lists, which the DMA fetches from host memory and
>> processes. Events such as descriptor completion and errors are signaled
>> using interrupts. The hardware detail is provided by
>> https://docs.xilinx.com/r/en-US/pg195-pcie-dma/Introduction
>>
>> This driver implements dmaengine APIs.
>> - probe the available DMA channels
>> - use dma_slave_map for channel lookup
>> - use virtual channel to manage dmaengine tx descriptors
>> - implement device_prep_slave_sg callback to handle host scatter gather
>> list
>> - implement device_config to config device address for DMA transfer
>>
>> Signed-off-by: Lizhi Hou <lizhi.hou@amd.com>
>> Signed-off-by: Sonal Santan <sonal.santan@amd.com>
>> Signed-off-by: Max Zhen <max.zhen@amd.com>
>> Signed-off-by: Brian Xu <brian.xu@amd.com>
>> ---
>> +/* bits of the channel control register */
>> +#define CHAN_CTRL_RUN_STOP BIT(0)
>> +#define CHAN_CTRL_IE_DESC_STOPPED BIT(1)
>> +#define CHAN_CTRL_IE_DESC_COMPLETED BIT(2)
>> +#define CHAN_CTRL_IE_DESC_ALIGN_MISMATCH BIT(3)
>> +#define CHAN_CTRL_IE_MAGIC_STOPPED BIT(4)
>> +#define CHAN_CTRL_IE_IDLE_STOPPED BIT(6)
>> +#define CHAN_CTRL_IE_READ_ERROR (0x1FUL << 9)
>> +#define CHAN_CTRL_IE_DESC_ERROR (0x1FUL << 19)
> Looks GENMASK()
Sure. Thanks for pointing it out.
>
>> +/* bits of the SG DMA control register */
>> +#define XDMA_CTRL_RUN_STOP BIT(0)
>> +#define XDMA_CTRL_IE_DESC_STOPPED BIT(1)
>> +#define XDMA_CTRL_IE_DESC_COMPLETED BIT(2)
>> +#define XDMA_CTRL_IE_DESC_ALIGN_MISMATCH BIT(3)
>> +#define XDMA_CTRL_IE_MAGIC_STOPPED BIT(4)
>> +#define XDMA_CTRL_IE_IDLE_STOPPED BIT(6)
>> +#define XDMA_CTRL_IE_READ_ERROR (0x1FUL << 9)
>> +#define XDMA_CTRL_IE_DESC_ERROR (0x1FUL << 19)
> Ditto.
>
>> +/**
>> + * xdma_config_channels - Detect and config DMA channels
>> + * @xdev: DMA device pointer
>> + * @dir: Channel direction
>> + */
>> +static int xdma_config_channels(struct xdma_device *xdev,
>> + enum dma_transfer_direction dir)
>> +{
>> + struct xdma_platdata *pdata = dev_get_platdata(&xdev->pdev->dev);
>> + u32 base, identifier, target;
>> + struct xdma_chan **chans;
>> + u32 *chan_num;
>> + int i, j, ret;
>> +
>> + if (dir == DMA_MEM_TO_DEV) {
>> + base = XDMA_CHAN_H2C_OFFSET;
>> + target = XDMA_CHAN_H2C_TARGET;
>> + chans = &xdev->h2c_chans;
>> + chan_num = &xdev->h2c_chan_num;
>> + } else if (dir == DMA_DEV_TO_MEM) {
>> + base = XDMA_CHAN_C2H_OFFSET;
>> + target = XDMA_CHAN_C2H_TARGET;
>> + chans = &xdev->c2h_chans;
>> + chan_num = &xdev->c2h_chan_num;
>> + } else {
>> + xdma_err(xdev, "invalid direction specified");
>> + return -EINVAL;
>> + }
>> +
>> + /* detect number of available DMA channels */
>> + for (i = 0, *chan_num = 0; i < pdata->max_dma_channels; i++) {
>> + ret = xdma_read_reg(xdev, base + i * XDMA_CHAN_STRIDE,
>> + XDMA_CHAN_IDENTIFIER, &identifier);
>> + if (ret) {
>> + xdma_err(xdev, "failed to read channel id: %d", ret);
>> + return ret;
>> + }
>> +
>> + /* check if it is available DMA channel */
>> + if (XDMA_CHAN_CHECK_TARGET(identifier, target))
>> + (*chan_num)++;
>> + }
>> +
>> + if (!*chan_num) {
>> + xdma_err(xdev, "does not probe any channel");
>> + return -EINVAL;
>> + }
>> +
>> + *chans = devm_kzalloc(&xdev->pdev->dev, sizeof(**chans) * (*chan_num),
>> + GFP_KERNEL);
>> + if (!*chans)
>> + return -ENOMEM;
>> +
>> + for (i = 0, j = 0; i < pdata->max_dma_channels; i++) {
>> + ret = xdma_read_reg(xdev, base + i * XDMA_CHAN_STRIDE,
>> + XDMA_CHAN_IDENTIFIER, &identifier);
>> + if (ret) {
>> + xdma_err(xdev, "failed to read channel id: %d", ret);
>> + return ret;
>> + }
> Is it ok to not rollback the allocation in case of an error occurs?

In this loop, the failures are returned by read/write registers. The
read/write register failure indicates serious hardware issue and the
hardware may not be rollback in this situation.

>
>> +
>> + if (!XDMA_CHAN_CHECK_TARGET(identifier, target))
>> + continue;
>> +
>> + if (j == *chan_num) {
>> + xdma_err(xdev, "invalid channel number");
>> + return -EIO;
>> + }
> Same here?
>
>> +
>> + /* init channel structure and hardware */
>> + (*chans)[j].xdev_hdl = xdev;
>> + (*chans)[j].base = base + i * XDMA_CHAN_STRIDE;
>> + (*chans)[j].dir = dir;
>> +
>> + ret = xdma_channel_init(&(*chans)[j]);
>> + if (ret)
>> + return ret;
> And here.
>
>> + (*chans)[j].vchan.desc_free = xdma_free_desc;
>> + vchan_init(&(*chans)[j].vchan, &xdev->dma_dev);
>> +
>> + j++;
>> + }
>> +
>> + dev_info(&xdev->pdev->dev, "configured %d %s channels", j,
>> + (dir == DMA_MEM_TO_DEV) ? "H2C" : "C2H");
>> +
>> + return 0;
>> +}
>
>> +static int xdma_irq_init(struct xdma_device *xdev)
>> +{
>> + u32 irq = xdev->irq_start;
>> + int i, j, ret;
>> +
>> + /* return failure if there are not enough IRQs */
>> + if (xdev->irq_num < xdev->h2c_chan_num + xdev->c2h_chan_num) {
>> + xdma_err(xdev, "not enough irq");
>> + return -EINVAL;
>> + }
>> +
>> + /* setup H2C interrupt handler */
>> + for (i = 0; i < xdev->h2c_chan_num; i++) {
>> + ret = request_irq(irq, xdma_channel_isr, 0,
>> + "xdma-h2c-channel", &xdev->h2c_chans[i]);
>> + if (ret) {
>> + xdma_err(xdev, "H2C channel%d request irq%d failed: %d",
>> + i, irq, ret);
>> + for (j = 0; j < i; j++) {
>> + free_irq(xdev->h2c_chans[j].irq,
>> + &xdev->h2c_chans[j]);
>> + }
>> + return ret;
> Remove freeing for loop and just do
> goto failed_init_c2h;
> And reverse the iteration order down on the error path (from i to zero) by
> using
> while (i--)
Thanks. This looks much cleaner than before. :)
>
>> + }
>> + xdev->h2c_chans[i].irq = irq;
>> + irq++;
>> + }
>> +
>> + /* setup C2H interrupt handler */
>> + for (i = 0; i < xdev->c2h_chan_num; i++) {
>> + ret = request_irq(irq, xdma_channel_isr, 0,
>> + "xdma-c2h-channel", &xdev->c2h_chans[i]);
>> + if (ret) {
>> + xdma_err(xdev, "H2C channel%d request irq%d failed: %d",
>> + i, irq, ret);
>> + for (j = 0; j < i; j++) {
>> + free_irq(xdev->c2h_chans[j].irq,
>> + &xdev->c2h_chans[j]);
>> + }
>> + goto failed_init_c2h;
> Ditto. But use j for this whole for loop so you can just do while (j--) on
> the error path as the index variable won't clash with the previous loop.
>
>> + }
>> + xdev->c2h_chans[i].irq = irq;
>> + irq++;
>> + }
>> +
>> + /* config hardware IRQ registers */
>> + ret = xdma_set_vector_reg(xdev, XDMA_IRQ_CHAN_VEC_NUM, 0,
>> + xdev->h2c_chan_num + xdev->c2h_chan_num);
>> + if (ret) {
>> + xdma_err(xdev, "failed to set channel vectors: %d", ret);
>> + goto failed;
>> + }
>> +
>> + /* enable interrupt */
>> + ret = xdma_enable_intr(xdev);
>> + if (ret) {
>> + xdma_err(xdev, "failed to enable interrupts: %d", ret);
>> + goto failed;
>> + }
>> +
>> + return 0;
>> +
>> +failed:
>> + for (i = 0; i < xdev->c2h_chan_num; i++)
> As mentioned above:
>
> while (j--)
>
>> + free_irq(xdev->c2h_chans[i].irq, &xdev->c2h_chans[i]);
>> +failed_init_c2h:
>> + for (i = 0; i < xdev->h2c_chan_num; i++)
> while (i--)
>
>> + free_irq(xdev->h2c_chans[i].irq, &xdev->h2c_chans[i]);
>> +
>> + return ret;
>> +}
>> +
>> +static bool xdma_filter_fn(struct dma_chan *chan, void *param)
>> +{
>> + struct xdma_chan *xdma_chan = to_xdma_chan(chan);
>> + struct xdma_chan_info *chan_info = param;
>> +
>> + if (chan_info->dir != xdma_chan->dir)
>> + return false;
>> +
>> + return true;
> return chan_info->dir == xdma_chan->dir;

Sure. I will change this.


Thanks,

Lizhi

>
>

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