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AM18X DMA for SDIO?

Shine Kao
Intellectual 405 points
Other Parts Discussed in Thread: AM1808

Hi,

We are testing Wi-Fi throughput and CPU loading on AM1808, and we runing Wi-Fi 11g mode(throughput is arround 21Mbps actually), the SW irq occupied 28% CPU time.

        Mem: 7956K used, 52968K free, 0K shrd, 1268K buff, 2276K cached

      CPU:   0% usr  44% sys    0% nic  14% idle   0% io  11% irq  28% sirq

In addition, we also check SDIO host driver, the DMA seems already enabled.

Do we have another way to ensure the SDIO DMA setting is corrected in our case? (through the register or ....)

Shine Kao

  • 0
    TI__Guru 62975 points

    Shine,

    Which OS driver are you using for this?

    -Tommy

  • 0 in reply to tlee
    Intellectual 405 points

    Tommy,

    We used Linux on this project.

    Thanks a lot.

    -Shine

  • 0 in reply to Shine Kao
    TI__Expert 4170 points

    Dear all,

     

    Following by the question start in this topic, the problem right now is the CPU loading of SDIO host controller will be too high while working with WiFi in high throughput.

    Our system needs to enable two SDIO devices working simutanously in high throughput. In the case, the CPU loading will be a bottleneck of this application which is a LTE  (SDIO interface 40Mbps is expected) to WiFi 802.11n (SDIO interface 40 Mbps is expected) router application.   

    Two questions we have:

    1. Is current SDIO driver (not SD memory) using DMA transfer already? The PSP benchmark number only shows memory transfer performance. 

    2. Is there any way to reduce CPU loading to keep two devices running smoothly? Any hints for system or driver?

     

    Best Regard,

    Rich

  • 0 in reply to Rich Chen
    Intellectual 670 points

    Rich,

          We have come across this issue and found that it was due to the busy wait loop in the file davinci_mmc.c. After making minor changes,  CPU load down was brought down considerably. I am not sure if this is the only reason for the CPU loading in your case. Anyway give a  try with this patch.

    Regards,

    N.Sugumar

  • 0 in reply to Sugumar Natarajan
    TI__Expert 4170 points

    Sugumar,

     

    Thanks for your patch. It does increase the idle time (it is supposed reduce CPU loading). However, the throughtput test result reduce dramastically.

    Downlink drops to half and uplink drops slightly. Do you have other idea or how to keep even increase throughtput without increase CPU loading.

     

    Best Regard,

    Rich