BUG: SD_write() and SD_read() will fail every 49.71026962962962962962 days.

[DOsbo]

Hi All,

I think SD_write() and SD_read() in sd_diskio.c (see below) have the timer tick overflow bug. For 30 seconds prior to osKernelSysTick() overflowing (every ~49 days), the functions will incorrectly return RES_ERROR without entering the while loop.

DRESULT SD_write(BYTE lun, const BYTE *buff, DWORD sector, UINT count)
{
  DRESULT res = RES_ERROR;
  osEvent event;
  uint32_t timer;
 
  if(BSP_SD_WriteBlocks_DMA((uint32_t*)buff,
                            (uint32_t) (sector),
                            count) == MSD_OK)
  {
    /* Get the message from the queue */
    event = osMessageGet(SDQueueID, SD_TIMEOUT);
 
    if (event.status == osEventMessage)
    {
      if (event.value.v == WRITE_CPLT_MSG)
      {
 
       //////////////////////////////////////////
       //    BAD JUJU 
       //////////////////////////////////////////
        timer = osKernelSysTick() + SD_TIMEOUT;
        /* block until SDIO IP is ready or a timeout occur */
        while(timer > osKernelSysTick())
        {
          if (BSP_SD_GetCardState() == SD_TRANSFER_OK)
          {
            res = RES_OK;
            break;
          }
        }
      }
    }
  }
 
  return res;
}
#endif /* _USE_WRITE == 1 */

It can be fixed by doing this:

       //////////////////////////////////////////
       //    GOOD JUJU 
       //////////////////////////////////////////
        timer = osKernelSysTick();
        /* block until SDIO IP is ready or a timeout occur */
        while((osKernelSysTick() - timer) <  SD_TIMEOUT)
        {
 
        }

I've only seen the bug in these 2 functions, so hopefully it's not a common occurrence. However, I think it would be wise to check all the other timeout functions.

Cheers,

David

[Tesla DeLorean]

>>so hopefully it's not a common occurrence.

You might hope, but I've been digging these types of logic errors out of the code for the best part of a decade.

The first HAL_Delay() implementation had this exact problem.