Increasing priority of a DMAC1 hardware request ID on RK3568?

Pavel Hofman pavel.hofman at ivitera.com
Wed Sep 6 10:37:38 PDT 2023


Dne 06. 09. 23 v 17:00 Pavel Hofman napsal(a):
> 
> Dne 06. 09. 23 v 10:42 Pavel Hofman napsal(a):
>> Please is it possible to increase a priority of a DMAC1 hardware 
>> request (I2S1_8ch_tx specifically) on RK3568? I could not find any 
>> DMAC priority mentioned in the RK3568 TRMs.
>>
> 
> 
> Unfortunately I could not find where this particular clock gets switched 
> to the non-default parent in the kernel code. Other clocks using the 
> same parents gpll200_gpll150_gpll100_xin24m_p (e.g. aclk_gic_audio) do 
> run at the default gpll_200m.
> 

Just an update - in the end I found the place - u-boot was setting that 
specific clock before booting linux 
https://github.com/radxa/u-boot/commit/65bd598f415b92d2165e52a757e70f85352eba25

I added clk_set_rate for "aclk_bus" back to 200MHz to clk-rk3568.c. 
However, the improvement of DMAC not keeping up with I2S transfers at 
768kHz samplerate was only marginal, still getting TXT FIFO underruns. 
Off to some different SoC :-(

Thanks a lot for your patience :-)

Pavel.



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