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L1 scratchpad for stack and RSI issues: bug in example rsi.c for BF504 (and possibly others)

boxeur
on Mar 23, 2013

Hi,

The example code to work with SD cards is using automatic variables (uint8_t buffer[8];) for DMA buffers. Of course, when the stack is in the scratchpad memory, that can't work.

Since the example code is very likely to be used as a basis for other applications, you might want to consider either making the buffer global or at least putting a big fat warning about the necessity to keep all DMA buffers out of automatic variables. I can also recommend adding a runtime assertion to ensure the address passed is in the right range.

It's likely that other drivers might suffer from similar problems so a more thorough investigation might be necessary.

Best regards.

    •  Analog Employees 
    on Apr 2, 2013 9:26 AM

    Hi,

    Can you confirm that you are referring to the POST example for the BF506F EZ-KIT Lite? If this is the case, I can enter an enhancement request so it can be considered for the future.

    Note that it may be beyond the scope of the examples to reiterate limitations - such as performing DMA from scratchpad - that are documented elsewhere.

    Regards,

    Craig.

  • on Apr 3, 2013 12:45 AM

    for example

     

    static uint32_t sd_mmc_get_sd_scr_register(void)

    {

        uint32_t error = 0;

        uint8_t buffer[8];

        *pRSI_DATA_LGTH = 8;

        *pRSI_DATA_TIMER = 0xFFFFFFFF;

        error = sd_mmc_send_command(SD_MMC_CMD_SEND_STATUS, adi_rsi_card_registers.sd.rca<<16);

        if((*pRSI_RESPONSE0 & SD_CSR_CURRENT_STATE) == SD_CSR_CURRENT_STATE_STANDBY)

        {

            error = sd_mmc_send_command(   SD_MMC_CMD_SELECT_DESELECT_CARD,

                                           adi_rsi_card_registers.sd.rca<<16);

        }

    // DMA call here

        SDBlockRead((void *)&buffer[0], 8);

  • on Apr 3, 2013 10:37 AM

    We declared them global and make static like this

    static uint8_t          dma_buffer[64];

    then remove    

    uint8_t buffer[8];

    or uint8_t buffer[64];


    from functions static uint32_t sd_mmc_get_sd_scr_register(void), static uint32_t sd_mmc_get_sd_ssr_register(void) and so on

    •  Analog Employees 
    on Apr 3, 2013 2:09 PM

    Thanks for the feedback. As I said, I'll log this as an enhancement request.

    Thanks again,

    Craig.