c47d7151d7
The EIC7700X is not cache coherent. No device that moves data on its own snoops the harts' caches or is snooped by them, so a buffer handed to a device needs the cache maintained around the transfer. The harts are coherent with each other; it is DMA that is not. The RISC-V standard offers no way to do that here: the Zicbom extension this core does not implement is the portable answer, and there is no other. Maintenance is instead a store to the L3 controller carrying the physical address of a cache block. That store is the only operation the hardware offers: it writes back and invalidates together, so a block cannot be dropped without being written out first. Everything built on top is shaped by that, which is why a range being invalidated has to own whole blocks. The L3 is inclusive of the L1 data cache and back invalidates it, so one store per block maintains the whole hierarchy, with nothing to do per hart. The block size is 64 bytes, which is what makes the descriptor rules in the storage and network drivers what they are. Assisted-by: Claude:claude-opus-5 Signed-off-by: Justin Hammond <justin@dynam.ac> |
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| binfmt | ||
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| cmake | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| dummy | ||
| fs | ||
| graphics | ||
| include | ||
| libs | ||
| mm | ||
| net | ||
| openamp | ||
| pass1 | ||
| sched | ||
| syscall | ||
| tools | ||
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| wireless | ||
| .asf.yaml | ||
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| .pre-commit-config.yaml | ||
| .yamllint | ||
| AUTHORS | ||
| CMakeLists.txt | ||
| CONTRIBUTING.md | ||
| INVIOLABLES.md | ||
| Kconfig | ||
| LICENSE | ||
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| README.md | ||
| ReleaseNotes | ||
Apache NuttX is a real-time operating system (RTOS) with an emphasis on standards compliance and small footprint. Scalable from 8-bit to 64-bit microcontroller environments, the primary governing standards in NuttX are POSIX and ANSI standards. Additional standard APIs from Unix and other common RTOSs (such as VxWorks) are adopted for functionality not available under these standards, or for functionality that is not appropriate for deeply-embedded environments (such as fork()).
For brevity, many parts of the documentation will refer to Apache NuttX as simply NuttX.
Getting Started
First time on NuttX? Read the Getting Started guide! If you don't have a board available, NuttX has its own simulator that you can run on terminal.
Documentation
You can find the current NuttX documentation on the Documentation Page.
Alternatively, you can build the documentation yourself by following the Documentation Build Instructions.
The old NuttX documentation is still available in the Apache wiki.
Supported Boards
NuttX supports a wide variety of platforms. See the full list on the Supported Platforms page.
Contributing
If you wish to contribute to the NuttX project, read the Contributing guidelines for information on Git usage, coding standard, workflow and the NuttX principles.
License
The code in this repository is under either the Apache 2 license, or a license compatible with the Apache 2 license. See the License Page for more information.