[GitHub] [incubator-nuttx] davids5 commented on pull request #3958: stm32h7:sdmmc: prevent SRAM123 and SRAM4 from using by SDMMC1 IDMA

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davids5 commented on pull request #3958:
URL: https://github.com/apache/incubator-nuttx/pull/3958#issuecomment-874853556


   @a-lunev I am looking into this on HW that supports SDMMC1. The code path where mmcsd_read_csd is for CONFIG_MMCSD_MMCSUPPORT. I have CONFIG_MMCSD_MMCSUPPORT disabled since there was a commit that broke the detection (while still in bitbucket).  Have you a config you can test this code path? 
   
   As I see it way to solve this are to a) use CONFIG_GRAN or b) statically define the buffer using locate_data.  The latter is more wasteful.
   
   My suggestion is to add CONFIG_GRAN and a dma allocattor. (see https://github.com/PX4/PX4-Autopilot/blob/master/platforms/nuttx/src/px4/common/board_dma_alloc.c) Then in mmcsd_read_csd add compile time code to call `board_dma_alloc` to alocate the buffer, then free it after use with board_dma_free.  


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