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

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Message-ID: <CAMuHMdXsUPAW5zKrsaTR9Tgv7kFdkz8s_QUjLXq6zDpoo47fRA@mail.gmail.com>
Date:   Tue, 21 Feb 2023 14:25:59 +0100
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Lizhi Hou <lizhi.hou@....com>
Cc:     vkoul@...nel.org, dmaengine@...r.kernel.org,
        linux-kernel@...r.kernel.org, max.zhen@....com,
        sonal.santan@....com, larry.liu@....com, brian.xu@....com,
        tumic@...see.org
Subject: Re: [RESEND PATCH V12 XDMA 1/2] dmaengine: xilinx: xdma: Add xilinx
 xdma driver

Hi Lizhi,

On Thu, Feb 9, 2023 at 8:18 PM Lizhi Hou <lizhi.hou@....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@....com>
> Signed-off-by: Sonal Santan <sonal.santan@....com>
> Signed-off-by: Max Zhen <max.zhen@....com>
> Signed-off-by: Brian Xu <brian.xu@....com>
> Tested-by: Martin Tuma <tumic@...see.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?

> +static const struct platform_device_id xdma_id_table[] = {
> +       { "xdma", 0},
> +       { },
> +};

This table is not needed, as the single entry matches driver.name below.

> +
> +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

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds