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SubjectRe: [RESEND PATCH V12 XDMA 1/2] dmaengine: xilinx: xdma: Add xilinx xdma driver
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On 2/21/23 05:25, Geert Uytterhoeven wrote:
> Hi Lizhi,
>
> On Thu, Feb 9, 2023 at 8:18 PM Lizhi Hou <lizhi.hou@amd.com> 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>
>> Tested-by: Martin Tuma <tumic@gpxsee.org>
> Thanks for your patch, which is now commit 17ce252266c7f016
> ("dmaengine: xilinx: xdma: Add xilinx xdma driver") in dmaengine/next.
>
>> --- a/drivers/dma/Kconfig
>> +++ b/drivers/dma/Kconfig
>> @@ -735,6 +735,20 @@ config XILINX_DMA
>> the scatter gather interface with multiple channels independent
>> configuration support.
>>
>> +config XILINX_XDMA
>> + tristate "Xilinx DMA/Bridge Subsystem DMA Engine"
>> + depends on HAS_IOMEM
>> + select DMA_ENGINE
>> + select DMA_VIRTUAL_CHANNELS
>> + select REGMAP_MMIO
> No platform dependencies at all, while this is a platform driver that
> relies on some other not-yet-existing driver creating an "xdma"
> platform device?
>
>> + help
>> + Enable support for Xilinx DMA/Bridge Subsystem DMA engine. The DMA
>> + provides high performance block data movement between Host memory
>> + and the DMA subsystem. These direct memory transfers can be both in
>> + the Host to Card (H2C) and Card to Host (C2H) transfers.
>> + The core also provides up to 16 user interrupt wires that generate
>> + interrupts to the host.
>> +
>> config XILINX_ZYNQMP_DMA
>> tristate "Xilinx ZynqMP DMA Engine"
>> depends on ARCH_ZYNQ || MICROBLAZE || ARM64 || COMPILE_TEST
>> --- /dev/null
>> +++ b/drivers/dma/xilinx/xdma.c
>> +/**
>> + * xdma_probe - Driver probe function
>> + * @pdev: Pointer to the platform_device structure
>> + */
>> +static int xdma_probe(struct platform_device *pdev)
>> +{
>> + struct xdma_platdata *pdata = dev_get_platdata(&pdev->dev);
> Platform data? No DT?
> Do we still accept plain platform drivers?

The XDMA driver needs to support both the non-DT and DT use cases.

For the non-DT case the parent PCIe device driver will create the xdma
platform device and pass the required information to the xdma driver. An
example is
https://lore.kernel.org/dmaengine/5fbe6029-61d5-bba4-556b-2282153f21dc@gpxsee.org/


For the DT use case, the xdma device will be populated by the FDT. This
part is WIP and will be enabled with future patches.

>
>> +static const struct platform_device_id xdma_id_table[] = {
>> + { "xdma", 0},
>> + { },
>> +};
> This table is not needed, as the single entry matches driver.name below.

Thanks. I will create a patch to fix this.


Lizhi

>
>> +
>> +static struct platform_driver xdma_driver = {
>> + .driver = {
>> + .name = "xdma",
>> + },
>> + .id_table = xdma_id_table,
>> + .probe = xdma_probe,
>> + .remove = xdma_remove,
>> +};
>> +
>> +module_platform_driver(xdma_driver);
> Gr{oetje,eeting}s,
>
> Geert
>

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