AM2634: CacheP operation of EDMA buffer

Lync

Part Number: AM2634

Hello,

I want to know how can I read the buffer values in interrupt of EDMA? I am a little confused by the cache operation. It seems the destination buffer is not updated if the CacheP_inv is not called before accessing to it.

Should I call CacheP_inv at beginning of the ISR to update the destination buffer then read from it, and then call CacheP_wb again before leaving the same ISR function?

And if so how about the time cost of the CacheP_inv and CacheP_wb API? This information it useful because the ISR is running at very high frequency.

Thanks.

Regards,

Lync

over 2 years ago

0 Sri Vidya Gunturi over 2 years ago

TI__Expert 7586 points

Hi Lync

We are looking into this. We will get back to you soon

Regards

Sri Vidya

+1 Sri Vidya Gunturi over 2 years ago in reply to Sri Vidya Gunturi

TI__Expert 7586 points

Hi Lync

EDMA doesn't copy from cache. It always copies from and to the actual physical memory.

So, if we are copying from a buffer to MMR, we do cache writeback so that the if the buffer is in cache, it gets moved to memory. Otherwise, DMA would copy the junk data in memory (when actual data is in cache).

Similarly, when copying from MMR to buffer, we do a cache invalidate.

To find the time cost of these APIs you can use the CPU cycle counter as shown below:

https://software-dl.ti.com/mcu-plus-sdk/esd/AM263X/latest/exports/docs/api_guide_am263x/KERNEL_DPL_CYCLE_COUNTER_PAGE.html

https://software-dl.ti.com/mcu-plus-sdk/esd/AM263X/latest/exports/docs/api_guide_am263x/group__KERNEL__DPL__CYCLE__COUNTER.html

Regards

Sri Vidya

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AM2634: CacheP operation of EDMA buffer