将Linux驱动程序DMA传输到以PC为主机的PCIe卡

问题描述

我正在研究DMA例程，以将数据从PC传输到PCIe卡上的FPGA.我阅读了DMA-API.txt和LDD3 ch.详情请参阅15.但是，我不知道如何进行从PC到PCIe卡上一致的iomem的DMA传输. LDD3中用于PCI的父亲示例映射了一个缓冲区，然后告诉卡进行DMA传输，但是我需要PC来执行此操作.

I am working on a DMA routine to transfer data from PC to a FPGA on a PCIe card. I read DMA-API.txt and LDD3 ch. 15 for details. However, I could not figure out how to do a DMA transfer from PC to a consistent block of iomem on the PCIe card. The dad sample for PCI in LDD3 maps a buffer and then tells the card to do the DMA transfer, but I need the PC to do this.

我已经发现的东西:

1. 请求总线主控器

1. Request bus master

pci_set_master(pdev);

设置DMA掩码

Set the DMA mask

if (dma_set_mask(&(pdev->dev), DMA_BIT_MASK(32))) {
    dev_err(&pdev->dev,"No suitable DMA available.\n");
    goto cleanup;
}

请求DMA通道

Request a DMA channel

if (request_dma(dmachannel, DRIVER_NAME)) {
    dev_err(&pdev->dev,"Could not reserve DMA channel %d.\n", dmachannel);
    goto cleanup;
}

映射用于DMA传输的缓冲区

Map a buffer for DMA transfer

dma_handle = pci_map_single(pci_dev, buffer, count, DMA_TO_DEVICE);

问题:

要让 PC 代替卡执行DMA传输，我该怎么办?

What do I have to do in order to let the PC perform the DMA transfer instead of the card?

感谢您的帮助！

首先，感谢您的答复.也许我应该更精确地提出我的问题:

First of all thank you for your replies. Maybe I should put my questions more precisely:

1. 据我了解，PC必须具有DMA控制器.如何访问此DMA控制器以开始向PCIe卡中的内存映射IO区域进行传输?
2. 我们的规范要求PC的DMA控制器启动传输.但是，我只能找到设备可以执行DMA工作的示例(DMA_mapping.txt，LDD3第15章).是否有原因，为什么没人使用PC的DMA控制器(尽管它仍然具有DMA通道)?为我们的项目要求更改规格会更好吗?

感谢您的耐心等候.

推荐答案

查找DMA_mapping.txt.在那里有一长段告诉您如何设置方向("DMA方向"，第408行).

Look up DMA_mapping.txt. There's a long section in there that tells you how to set the direction ('DMA direction', line 408).

编辑

好的，因为您已经编辑了问题...您的说明是错误的.您可以设置系统DMA控制器，但这将毫无意义，因为它太慢了，正如我在评论中所说.阅读此线程.

Ok, since you edited your question... your specification is wrong. You could set up the system DMA controller, but it would be pointless, because it's too slow, as I said in the comments. Read this thread.

您必须更改FPGA以支持总线主控.我这样做是为了谋生-如果您想分包合同，请与我联系.

You must change your FPGA to support bus mastering. I do this for a living - contact me off-thread if you want to sub-contract.

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