Linux/AM3352: GPMC DMA transfer triggered by GPIO

Dachuan Liu

Part Number: AM3352

Tool/software: Linux

CPU：AM335x

Linux Kernel：4.4.10

I'm working on am335x's dma, my goal is to use a gpio interrupt to trigger a EDMA's mem to mem transfer, that copying 8 bytes from GPMC SRAM to ram.

The trigger gpio is GP2[29], which is a indirect mapped dma event.

I add the dma binding code in dts file:

dma_test {
	compatible = "cet,am335x-dma-test";
	status = "okay";
	dmas = <&edma_xbar 32 0 32>;
	dma-names = "dma_test";
};

My test code is listed below, I have tried two methods to request a dma channel, but have different result.

 dma_cap_zero(mask);
    dma_cap_set(DMA_MEMCPY, mask);
/* !!!!!!!!!!!!!!!!!!!!!! */
/* Method 1: dma_request_channel without any param */
    dma_ch = dma_request_channel(mask, 0, NULL);
/* Methed 2: dma_request_chan, which can obtain dma channel info. specified in dts file */
    dma_ch = dma_request_chan(&pdev->dev, "dma_test");/* no place to pass mask */

    if (dma_ch == NULL)
    {
        printk("request_channel failed.\n");
        goto err;
    }
    printk("got dma_ch = 0x%x\n", dma_ch);


    rxconf.src_addr = ADC_ADDR;
    rxconf.dst_addr = dma_buf_phys_addr;
    rxconf.src_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE;
    rxconf.dst_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE;
    rxconf.src_maxburst = 1;
    rxconf.dst_maxburst = 1;
    rxconf.device_fc = 0;
    rxconf.slave_id = 0;

    ret = dmaengine_slave_config(dma_ch, &rxconf);
    if (ret)
        goto err;
    printk("dmaengine_slave_config pass.\n");


    /* debug: print device struct info */
    dma_ch_debug(dma_ch);

    if (dma_ch->device->device_prep_dma_memcpy == NULL)
    {
        printk("device_prep_dma_memcpy = NULL\n");
        goto err;
    }

    tx_desc = dma_ch->device->device_prep_dma_memcpy(dma_ch, dma_buf_phys_addr, ADC_ADDR,
                            8, DMA_CTRL_ACK | DMA_PREP_INTERRUPT);
    if (!tx_desc)
        goto err;
    printk("device_prep_dma_memcpy pass.\n");

    tx_desc->callback = dma_callback_func;
    tx_desc->callback_param = NULL;

    cookie = tx_desc->tx_submit(tx_desc); //submit the desc
    if (dma_submit_error(cookie)){
        printk(KERN_INFO "Failed to do DMA tx_submit");
        goto err;
    }

    printk("tx_submit pass.\n");

    dma_async_issue_pending(dma_ch);

When I use dma_request_channel() API, I get a memcpy only dma channel:

[ 1349.049411] Key get value 1
[ 1349.060336] read 8 bytes:
[ 1349.063125] 00 05 c1 13 0b 60 f0 5b 
[ 1349.074218] got dma_buf = 0xf0ea8000 dma_buf_phys_addr = 0xbd042000
[ 1349.085953] got dma_ch = 0xee9715f0
[ 1349.092285] dmaengine_slave_config pass.
[ 1349.096434] device = 0xee93dcd0
[ 1349.104284] device->chancnt = 2
[ 1349.110178] device->dev_id = 1
[ 1349.113406] device->dev = 0xee90fa10
[ 1349.121617] device->filter = 0x00000000
[ 1349.125670] device->cap_mask = 0x601    //  !!
[ 1349.133862] device->device_config = 0xc02598c4
[ 1349.141089] device->device_prep_dma_memcpy=0xc0259938   //  !!
[ 1349.146424] device->device_prep_slave_sg = 0x00000000          //  !!
[ 1349.156189] device->device_prep_slave_cyclic = 0x00000000    //  !!
[ 1349.164455] tx_submit pass.
[ 1349.170017] 00 05 c1 13 0b 60 f0 5b

It can start a mem_to_mem transfer but without GPIO trigger.
The cap_mask is only DMA_MEMCPY, DMA_ASYNC_TX..

When I use dma_request_chanl() API, I get a hw triggered dma channel but it does not have device_prep_dma_memcpy() function registed.
The cap_mask is 0x1E00, which DMA_MEMCPY bit is not set.

[ 1373.798536] Key get value 1
[ 1373.810160] read 8 bytes:
[ 1373.812952] 00 05 c1 13 0b 60 f0 5b 
[ 1373.824948] got dma_buf = 0xf0eca000 dma_buf_phys_addr = 0xbd042000
[ 1373.834724] got dma_ch = 0xee972310
[ 1373.841227] dmaengine_slave_config pass.
[ 1373.845376] device = 0xee94f044
[ 1373.853261] device->chancnt = 62
[ 1373.859267] device->dev_id = 0
[ 1373.862495] device->dev = 0xee90fa10
[ 1373.866261] device->filter = 0xc025a2bc
[ 1373.876557] device->cap_mask = 0x1e00     //   !! 
[ 1373.883061] device->device_config = 0xc02598c4
[ 1373.890323] device->device_prep_dma_memcpy=0x00000000  //  !!
[ 1373.895657] device->device_prep_slave_sg = 0xc0259f8c           //  !!
[ 1373.905423] device->device_prep_slave_cyclic = 0xc0259b90    // !!
[ 1373.913609] device_prep_dma_memcpy = NULL

Question:

How can I get a event binded DMA_MEMCPY channel using dmaengine API?

over 8 years ago