linux-kernel - Re: [PATCH V12 1/1] dmaengine: amd: qdma: Add AMD QDMA driver

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Message-ID: <420b4788-a054-ce74-29c9-eb8f1b7aa173@amd.com>
Date: Fri, 27 Sep 2024 11:18:48 -0700
From: Lizhi Hou <lizhi.hou@....com>
To: Geert Uytterhoeven <geert@...ux-m68k.org>
CC: <nishad.saraf@....com>, <vkoul@...nel.org>, <dmaengine@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, Nishad Saraf <nishads@....com>,
	<sonal.santan@....com>, <max.zhen@....com>
Subject: Re: [PATCH V12 1/1] dmaengine: amd: qdma: Add AMD QDMA driver

Hi Geert,


On 9/27/24 02:01, Geert Uytterhoeven wrote:
> Hi Lizhi,
>
> On Tue, Sep 3, 2024 at 6:50 PM Lizhi Hou <lizhi.hou@....com> wrote:
>> On 9/3/24 02:20, Geert Uytterhoeven wrote:
>>> On Thu, Apr 18, 2024 at 7:51 PM Lizhi Hou <lizhi.hou@....com> wrote:
>>>> From: Nishad Saraf <nishads@....com>
>>>>
>>>> Adds driver to enable PCIe board which uses AMD QDMA (the Queue-based
>>>> Direct Memory Access) subsystem. For example, Xilinx Alveo V70 AI
>>>> Accelerator devices.
>>>>       https://www.xilinx.com/applications/data-center/v70.html
>>>>
>>>> The QDMA subsystem is used in conjunction with the PCI Express IP block
>>>> to provide high performance data transfer between host memory and the
>>>> card's DMA subsystem.
>>>>
>>>>               +-------+       +-------+       +-----------+
>>>>      PCIe     |       |       |       |       |           |
>>>>      Tx/Rx    |       |       |       |  AXI  |           |
>>>>    <=======>  | PCIE  | <===> | QDMA  | <====>| User Logic|
>>>>               |       |       |       |       |           |
>>>>               +-------+       +-------+       +-----------+
>>>>
>>>> The primary mechanism to transfer data using the QDMA is for the QDMA
>>>> engine to operate on instructions (descriptors) provided by the host
>>>> operating system. Using the descriptors, the QDMA can move data in both
>>>> the Host to Card (H2C) direction, or the Card to Host (C2H) direction.
>>>> The QDMA provides a per-queue basis option whether DMA traffic goes
>>>> to an AXI4 memory map (MM) interface or to an AXI4-Stream interface.
>>>>
>>>> The hardware detail is provided by
>>>>       https://docs.xilinx.com/r/en-US/pg302-qdma
>>>>
>>>> Implements dmaengine APIs to support MM DMA transfers.
>>>> - 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
>>>>
>>>> Signed-off-by: Nishad Saraf <nishads@....com>
>>>> Signed-off-by: Lizhi Hou <lizhi.hou@....com>
>>> Thanks for your patch, which is now commit 73d5fc92a11cacb7
>>> ("dmaengine: amd: qdma: Add AMD QDMA driver") in dmaengine/next.
>>>
>>>> --- /dev/null
>>>> +++ b/drivers/dma/amd/Kconfig
>>>> @@ -0,0 +1,14 @@
>>>> +# SPDX-License-Identifier: GPL-2.0-only
>>>> +
>>>> +config AMD_QDMA
>>>> +       tristate "AMD Queue-based DMA"
>>>> +       depends on HAS_IOMEM
>>> Any other subsystem or platform dependencies, to prevent asking the
>>> user about this driver when configuring a kernel for a system which
>>> cannot possibly have this hardware?
>>> E.g. depends on PCI, or can this be used with other transports than PCIe?
>> No, this driver does not have other dependencies. It can be used with
>> other transports.
>>
>> It is similar with dmaengine/xilinx/xdma
> OK.
>
>>>> --- /dev/null
>>>> +++ b/drivers/dma/amd/qdma/qdma-comm-regs.c
>>>> +static struct platform_driver amd_qdma_driver = {
>>>> +       .driver         = {
>>>> +               .name = "amd-qdma",
>>> Which code is responsible for creating "amd-qdma" platform devices?
> I still would like to receive an answer to this question?
> Thanks!

Sorry, I missed this question.

The driver of device which uses qdma IP will create amd-qdma platform 
device. E.g. for our FPGA device:

https://github.com/houlz0507/XRT-1/blob/qdma_v2_usage/src/runtime_src/core/pcie/driver/linux/xocl/subdev/qdma.c#L614


Thanks,

Lizhi

>
>
> 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