About bittiming calculation result

Hi,

I have a question for bittiming-value calculated by Can-core.

In case setting like below,
 - ip link set can0 type can bitrate 800000
 - clock=50MHz
 - Use pch_can

Can-core calculates like below
brp=21
seg1=1
seg2=1
sjw=1
prop_seg=0

Is "prop_seg=0" true ?
seg1/seg2/sjw/prop_seg must be more than 1 ?

Also I can see the following kernel error log.
bitrate error 0.7%

Thanks,
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Tomoya MORINAGA
OKI SEMICONDUCTOR CO., LTD.