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Posted to commits@nuttx.apache.org by GitBox <gi...@apache.org> on 2021/11/25 12:44:22 UTC

[GitHub] [incubator-nuttx] davids5 commented on pull request #4878: cache_invalidate: fix unalign cacheline invalidate & add cache coherence config for semihosting option

davids5 commented on pull request #4878:
URL: https://github.com/apache/incubator-nuttx/pull/4878#issuecomment-979182621


   @xiaoxiang781216 Would you please explain (with an example) what problem this is solving? 
   
   It is fundamentally incorrect (and was prior to the change). Backing the start pointer up should never happen, because it will invalidate the cache BEFOR the callers data structure. In a system configure as writeback (This should be all M7 with the errata*) it will corrupt a dirty cache line.
     
   
   
   
   
   ```
   *Errata 1259864
   Data corruption in a sequence of Write-Through stores and loads
   Status
   Affects: Cortex-M7, Cortex-M7 with FPU Fault Type: Programmer Category A
   Fault Status: Present in r0p1, r0p2, r1p0 and r1p1. Fixed in r1p2.
   ```


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