Date:   Wed, 12 Oct 2022 15:50:06 +0200
From:   Martin Tůma <tumic@...see.org>
To:     Lizhi Hou <lizhi.hou@....com>, vkoul@...nel.org,
        dmaengine@...r.kernel.org, linux-kernel@...r.kernel.org,
        trix@...hat.com
Cc:     max.zhen@....com, sonal.santan@....com, larry.liu@....com,
        brian.xu@....com
Subject: Re: [PATCH V6 XDMA 0/2] xilinx XDMA driver

On 11. 10. 22 17:27, Lizhi Hou wrote:
> 
> On 10/7/22 06:21, Martin Tůma wrote:
>> On 06. 10. 22 19:42, Lizhi Hou wrote:
>>>
>>> On 10/6/22 09:37, Martin Tůma wrote:
>>>> On 04. 10. 22 23:43, Lizhi Hou wrote:
>>>>> Hello,
>>>>>
>>>>> This V6 of patch series is to provide the platform driver to 
>>>>> support the
>>>>> Xilinx XDMA subsystem. The XDMA 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. It also provides up to 16 user
>>>>> interrupt wires to user logic that generate interrupts to the host.
>>>>>
>>>>>              +-------+       +-------+       +-----------+
>>>>>     PCIe     |       |       |       |       |           |
>>>>>     Tx/Rx    |       |       |       |  AXI  |           |
>>>>>   <=======>  | PCIE  | <===> | XDMA  | <====>| User Logic|
>>>>>              |       |       |       |       |           |
>>>>>              +-------+       +-------+       +-----------+
>>>>>
>>>>> The XDMA has been used for Xilinx Alveo PCIe devices.
>>>>> And it is also integrated into Versal ACAP DMA and Bridge Subsystem.
>>>>> https://www.xilinx.com/products/boards-and-kits/alveo.html
>>>>> https://docs.xilinx.com/r/en-US/pg344-pcie-dma-versal/Introduction-to-the-DMA-and-Bridge-Subsystems
>>>>>
>>>>> The device driver for any FPGA based PCIe device which leverages 
>>>>> XDMA can
>>>>> call the standard dmaengine APIs to discover and use the XDMA 
>>>>> subsystem
>>>>> without duplicating the XDMA driver code in its own driver.
>>>>>
>>>>> Changes since v5:
>>>>> - Modified user logic interrupt APIs to handle user logic IP which 
>>>>> does not
>>>>>    have its own register to enable/disable interrupt.
>>>>> - Clean up code based on review comments.
>>>>>
>>>>> Changes since v4:
>>>>> - Modified user logic interrupt APIs.
>>>>>
>>>>> Changes since v3:
>>>>> - Added one patch to support user logic interrupt.
>>>>>
>>>>> Changes since v2:
>>>>> - Removed tasklet.
>>>>> - Fixed regression bug introduced to V2.
>>>>> - Test Robot warning.
>>>>>
>>>>> Changes since v1:
>>>>> - Moved filling hardware descriptor to xdma_prep_device_sg().
>>>>> - Changed hardware descriptor enum to "struct xdma_hw_desc".
>>>>> - Minor changes from code review comments.
>>>>>
>>>>> Lizhi Hou (2):
>>>>>    dmaengine: xilinx: xdma: Add xilinx xdma driver
>>>>>    dmaengine: xilinx: xdma: Add user logic interrupt support
>>>>>
>>>>>   MAINTAINERS                            |   11 +
>>>>>   drivers/dma/Kconfig                    |   13 +
>>>>>   drivers/dma/xilinx/Makefile            |    1 +
>>>>>   drivers/dma/xilinx/xdma-regs.h         |  171 ++++
>>>>>   drivers/dma/xilinx/xdma.c              | 1034 
>>>>> ++++++++++++++++++++++++
>>>>>   include/linux/dma/amd_xdma.h           |   16 +
>>>>>   include/linux/platform_data/amd_xdma.h |   34 +
>>>>>   7 files changed, 1280 insertions(+)
>>>>>   create mode 100644 drivers/dma/xilinx/xdma-regs.h
>>>>>   create mode 100644 drivers/dma/xilinx/xdma.c
>>>>>   create mode 100644 include/linux/dma/amd_xdma.h
>>>>>   create mode 100644 include/linux/platform_data/amd_xdma.h
>>>>>
>>>>
>>>> Hi,
>>>> I have rewritten our V4L2 driver to use this new XDMA driver, but it 
>>>> does not work on our HW (where the previous Xilinx XDMA driver 
>>>> derived from the Xilinx sample code worked fine). The driver is 
>>>> sucessfully loaded and 4(2+2) DMA channels are successfully created. 
>>>> But when a DMA transfer is initiated, I get an error from my PC's 
>>>> DMA chip:
>>>>
>>>> AMD-Vi: Event logged [IO_PAGE_FAULT domain=0x000a address=0x36a00000 
>>>> flags=0x0000]
>>>>
>>>> and no error from XDMA.
>>>>
>>>> Does the driver expect some special FPGA IP core configuration? Or 
>>>> is there something else I'm missing? My code is quiet similar to 
>>>> what you use in your XRT repo on GitHub (there is btw. a bug in the 
>>>> XRT code - you do not clear the dma_slave_config struct before 
>>>> using) but in my case the DMA transfer triggers the AMD-Vi error and 
>>>> timeouts.
>>>>
>>>> The code of our driver is attached, the relevant parts are in 
>>>> mgb4_dma.c
>>>> and mgb4_core.c.
>>>>
>>>> M.
>>>
>>> Hi Martin,
>>>
>>> Thanks for trying this and got a lot thing works. I have read your 
>>> driver. Could you call pci_map_sg() before calling prep_sg()? (and 
>>> pci_unmap_sg()) after transfer complete?
>>>
>>> example: 
>>> https://github.com/houlz0507/XRT-1/blob/xdma_v4_usage/src/runtime_src/core/pcie/driver/linux/xocl/subdev/xdma.c#L103
>>>
>>>
>>> Thanks,
>>>
>>> Lizhi
>>>
>>
>> Hi,
>> That's not the problem, the sg is already mapped by V4L2 videobuf-dma-sg
>> (https://elixir.bootlin.com/linux/v6.0/source/drivers/media/v4l2-core/videobuf-dma-sg.c#L285). With the original XDMA driver I was also not mapping the sg and it worked fine. And yes, I have tried it anyway and it didn't help ;-)
>>
>> So there must be some other problem in your XDMA driver.
>>
>> M.
> 
> Hi Martin,
> 
> I got a AMD server and debug this issue. And there is indeed a XDMA 
> driver issue. My DMA test passed on this server after fixing the issue. 
> I will post v7 patches and hopefully that fixes the issue you have seen 
> as well.
> 
> Thanks for trying the driver.
> 
> Lizhi
> 

Hi,
Even the newest version (v7) still does not work with our card. The 
error is the same.

M.

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