Re: [RESEND PATCH V12 XDMA 1/2] dmaengine: xilinx: xdma: Add xilinx xdma driver

[Lizhi Hou]

On 2/21/23 05:25, Geert Uytterhoeven wrote:
> Hi Lizhi,
>
> On Thu, Feb 9, 2023 at 8:18 PM Lizhi Hou <lizhi.hou@xxxxxxx> 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@xxxxxxx>
> > Signed-off-by: Sonal Santan <sonal.santan@xxxxxxx>
> > Signed-off-by: Max Zhen <max.zhen@xxxxxxx>
> > Signed-off-by: Brian Xu <brian.xu@xxxxxxx>
> > Tested-by: Martin Tuma <tumic@xxxxxxxxxx>
> 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@xxxxxxxxxx/ 


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