How to request irq for ep device?

[william.fang]

In jetson sdk 32.5,
drivers/pci/endpoint/functions/pci-epf-tegra-vnet.c file uses polling for dma write completed as follows:

dma_common_wr8(tvnet->dma_base, DMA_WR_DATA_CH, DMA_WRITE_DOORBELL_OFF);             |                   ((transfer->dst_iova_addr >> 32) & 0xFFFFFFFF),
    desc_cnt->wr_cnt++;                                                                  |                   DMA_DAR_HIGH_OFF_WRCH);
                                                                                         |
    while (true) {                                                                       |    /* ring the door bell with channel number */
        val = dma_common_rd(tvnet->dma_base, DMA_WRITE_INT_STATUS_OFF);                  |    ep_dma_common_wr8(rc_xdma->dma_base, channel, DMA_WRITE_DOORBELL_OFF);
        if (val == BIT(DMA_WR_DATA_CH)) {                                                |
            dma_common_wr(tvnet->dma_base, val,                                          |    now = jiffies;
                      DMA_WRITE_INT_CLEAR_OFF);                                          |    while (true) {
            break;                                                                       |        val = ep_dma_common_rd(rc_xdma->dma_base, DMA_WRITE_INT_STATUS_OFF);
        }                                                                                |        if (BIT(channel) & val) {
        if (time_after(jiffies, timeout)) {                                              |            ep_dma_common_wr(rc_xdma->dma_base, val, DMA_WRITE_INT_CLEAR_OFF);
            dev_err(fdev, "dma took more time, reset dma engine\n");                     |            break;
            dma_common_wr(tvnet->dma_base,                                               |        }
                      DMA_WRITE_ENGINE_EN_OFF_DISABLE,                                   |
                      DMA_WRITE_ENGINE_EN_OFF);                                          |        if (time_after(jiffies, now + timeout)) {
            mdelay(1);                                                                   |            pr_err("DMA write timed out & poll end\n");
            dma_common_wr(tvnet->dma_base,                                               |            ep_dma_common_wr(rc_xdma->dma_base, DMA_WRITE_ENGINE_EN_OFF_DISABLE,
                      DMA_WRITE_ENGINE_EN_OFF_ENABLE,                                    |                      DMA_WRITE_ENGINE_EN_OFF);
                      DMA_WRITE_ENGINE_EN_OFF);                                          |            mdelay(1);
            desc_cnt->wr_cnt--;                                                          |            ep_dma_common_wr(rc_xdma->dma_base, DMA_WRITE_ENGINE_EN_OFF_ENABLE,
            pci_epc_unmap_addr(epc, tvnet->tx_dst_pci_addr);                             |                      DMA_WRITE_ENGINE_EN_OFF);
            dma_unmap_single(cdev, src_iova, len, DMA_TO_DEVICE);                        |            return -ETIMEDOUT;
            return NETDEV_TX_BUSY;                                                       |        }
        }                                                                                |    }
    }```

But I want to use interrupt by request_irq method instead of polling. What I should do to relize it?

[vidyas]

We are using NAPI for better performance, hence you may see the polling logic. But, it is not pure polling, rather a hybrid way of using interrupts and polling.
Any specific reason why you want to use interrupts only? (which gives lesser performance compared to NAPI)

[william.fang]

Hi, vidyas,

I’m sorry to response to you so late.
I don’t understand what you mean. We judge whether the data transmission is completed by polling DMA_WRITE_INT_STATUS_OFF register. Is it related to interruption?

[william.fang]

The problem of polling DMA_WRITE_INT_STATUS_OFF register is that cpu utilization reaches 99%.