Add support for using noinit variables in SPIRAM (IDFGH-2654) #4728
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Add Kconfig option SPIRAM_ALLOW_NOINIT_EXTERNAL_MEMORY When enabled, a new linker script rule (from esp32.extram.noinit.ld) places any variables in the .ext_ram.noinit section in SPIRAM. This section is exempted from the startup SPIRAM memory test and is not zero-initialized or added to the malloc pool, making it usable for noinit variables that persist across reset. The EXT_RAM_NOINIT_ATTR macro places variables in this section.
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Thanks for your contribution, changes have been merged with 0dad763. |
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Resolution: Done
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As per #4700, this pull request add support for placing non-initialized variables in SPIRAM.
This includes the following changes:
SPIRAM_ALLOW_NOINIT_EXTERNAL_MEMORYwhich enables the feature.EXT_RAM_NOINIT_ATTRcan be used to place variables into a new non-initialized section in SPIRAM. IfSPIRAM_ALLOW_NOINIT_EXTERNAL_MEMORYis disabled, it attempts to place it in regular internal RAM instead.I've tested this internally and I've found it works pretty well (with the caveat that it's important to flush the SPIRAM write-back cache before restarting to ensure everything has been written back) and I've added a simple unit test for it.
Caveats: