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Reconfiguring EDMA channel allocation on ARM

_Ralph_
Guru 10685 points

I am trying to move more EDMA/TCC channels to the DSP side so that my channel-hungry algorithm can work.


I tried to follow this guide:

http://processors.wiki.ti.com/index.php/Reconfiguring_EDMA_channel_allocation_on_ARM

however this is for a much older kernel than the one I have at the moment (from DVSDK 3.11.00.19). My question is, which file should I edit to give more EDMA channels to my DSP (DM6467)?

I have found DM646x.c in the kernel source with the DVSDK and this has some information that looks like it might be relevant however the resource allocations in that file do not match what I have in real life. For example, in this C file there is this interesting snippet of code:

static const s8 dm646x_dma_rsv_chans[][2] = {
    /* (offset, length) */
    { 0,  4},
    {13,  3},
    {24,  4},
    {30,  2},
    {54,  3},    /* 16 total length */
    {-1, -1}
};

static const s16 dm646x_dma_rsv_slots[][2] = {
    /* (offset, length) */
    { 0,  4},
    {13,  3},
    {24,  4},
    {30,  2},
    {54,  3},
    {128, 384},    /*400 total length */
    {-1, -1}
};

When I actually see my DMA channels get allocated I see this (the channels are allocated in the order shown below):

{ 0,  4},
{13,  3},
{20, 14},
{46,  8},
{56,  8},  /* 37 total length */

{-1, -1}

This is also at odds with the information provided in the link I gave above.

Any suggestions of how/where I should be allocating my DMA channels in the kernel source?

Just what is dm646x_dma_rsv_slots? Something to do with PaRAMs?

Thanks,
Ralph

  • 0
    TI__Expert 5170 points

    Hi,

    Ralph said:
    static const s8 dm646x_dma_rsv_chans[][2] = {
        /* (offset, length) */
        { 0,  4},
        {13,  3},
        {24,  4},
        {30,  2},
        {54,  3},    /* 16 total length */
        {-1, -1}
    };

    This table says that starting from channel no. 0, 4 channels are reserved for DSP side. So if you want more channels reserved for DSP, then you should modify the above table.

    As you have mentioned dm646x_dma_rsv_slots refers to the reserved PaRAMs for DSP side.

    Regards, Sudhakar

  • 0 in reply to Sudhakar Rajashekhara
    Guru 10685 points

    Okay, thanks for that but why does my kernel source code seem to imply that there are only 16 channels reserved for the DSP when in actual fact I see 37 being allocated (and then the program crashes as it can't allocate any more)?

    Ralph

  • 0 in reply to _Ralph_
    Guru 10685 points

    While I'm here, what also confuses me is why in the cs2dm6467_1_00_00_10 server directory do the EDMA3.maxTccs and EDMA3.maxEdmaChannels variables specify 49 as their value when the dm646x.c file implies only 16 channels available for the DSP. This is surely a bug in one of these files?


    Ralph