CDO

I'm trying to calculate ECAR90P - Wet days wrt 90th percentile of reference period - eca_r90p ifile1 ifile2 ofile
"Let ifile1 be a time series of daily precipitation amounts RR, and ifile2 be the 90th percentile RRn90 of daily precipitation amounts at wet days for any period used as reference. Then calculated is the percentage of wet days with RR > RRn90. RRn90 is calculated as the 90th percentile of all wet days of a given climate reference period."

At the moment I've calculate RRn90 with timpctl,90. Thus it is not the 90th percentile of all wet days but of all days (am I right here?). However, this gives me the following error:

cdo eca_r90p (Abort): Input streams have different number of time steps!

I'd also like to calculate RRn90 as the 90th percentile of all wet days. Is there a function for this within CDO?
And how do I solve the current problem?

Thanks in advance, Emma