Cache

Table of Contents

• Features Supported
• Features NOT Supported
• Important Usage Guidelines
• Example Usage
• API

Features Supported

• APIs to perform below cache operations
  • region based writeback
  • region based invalidate
  • region based writeback invalidate
  • enable and disable APIs for I cache and D cache
  • full cache writeback, write invalidte

Features NOT Supported

NA

Important Usage Guidelines

• The region based cache APIs, CacheP_wb, CacheP_wbInv, CacheP_inv, operate on a CPU cache line, hence its strongly recommended to make sure 'addr' is cache line aliged and 'size` is a multiple of cache line size
  • Start address is calculated as follows, start_addr = floor(addr, CPU_CACHE_LINE)
  • End address is calculated as follows, end_addr = ceil(addr + size, CPU_CACHE_LINE)
  • No error is returned, for unaligned addr and size
• On R5F,
  • Valid values for CacheP_Type for CacheP_enable and CacheP_disable are CacheP_TYPE_L1D, CacheP_TYPE_L1P, CacheP_TYPE_ALL
  • Valid values for CacheP_Type for CacheP_wb, CacheP_wbInv, CacheP_inv, CacheP_wbAll, CacheP_wbInvAll are CacheP_TYPE_L1D, CacheP_TYPE_ALL
• CPU cache lines sizes for reference
  • R5F: 32B
  • A53: 64B
• On R5F, It is recommended to enable both program and data cache in R5F in all applications. In R5F for cache to be enabled MPU needs to be enabled.
• On M4F, the CPU does not support cache so these APIs when used with M4F, will be blank and will have no effect

Example Usage

Include the below file to access the APIs,

#include <kernel/dpl/CacheP.h>

Example usage for cache write back invalidate,

    char buf[1024];
 
    void * addr = buf;
    uint32_t size = sizeof(buf);
 
    // addr = cache line aligned buffer address
    // size = multiple of cache line aligned size in bytes
    // flush contents of cache to memory so that a DMA or HW peripheral can see the data
    CacheP_wbInv(addr, size, CacheP_TYPE_ALL);
 
    // send data to DMA or HW peripheral

Example usage for cache invalidate,

    // ...
    // recieve data from DMA or HW peripheral
    // addr = cache line aligned buffer address
    // size = multiple of cache line aligned size in bytes
    // invalidate contents of cache so that a CPU can see the data written by DMA or HW peripheral
 
    CacheP_inv(addr, size, CacheP_TYPE_ALL);

API

APIs for Cache,