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

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a-lunev commented on pull request #3958:
URL: https://github.com/apache/incubator-nuttx/pull/3958#issuecomment-864997606


   > @a-lunev - Why is this needed when stm32_dmapreflight already excludes it?
   Hi David,
   stm32_dmapreflight() depends on the CONFIG_STM32H7_SDMMC_IDMA option that as I understand should not do, because IDMA is still in use not depending on the option.
   Also stm32_dmapreflight() is invoked olny if CONFIG_DEBUG_ASSERTIONS option is enabled.
   If my understanding is correct, concerning namely SDMMC1 IDMA, stm32_dmapreflight() is useful for debug purposes to check if IDMA is trying to access not allowed memory regions like SRAM123 and SRAM4. This can be caught only if CONFIG_DEBUG_ASSERTIONS option is enabled.
   In a normal build CONFIG_DEBUG_ASSERTIONS option is not enabled. How then the system should be prevented from the IDMA access failure?
   On another hand, if CONFIG_DEBUG_ASSERTIONS option is enabled and the assert triggered, what the further developer actions should be in this particular case with SDMMC1 IDMA? As I understand, normally there are two possible options:
   - either to exclude SRAM123 and/or SRAM4 from the heap allocation;
   - or to use SDMMC2 instead of SDMMC1 as SDMMC2 does not have the access limitation.
   
   Please let me know what do you think.


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