SSIFSR
fifo_samples = (rz_ssi_reg_readl(ssi, SSIFSR) >>
rz_ssi_reg_mask_setl(ssi, SSIFSR, SSIFSR_RDF, 0);
ssifsr = rz_ssi_reg_readl(ssi, SSIFSR);
rz_ssi_reg_mask_setl(ssi, SSIFSR, SSIFSR_TDE, 0);
rz_ssi_reg_mask_setl(ssi, SSIFSR, SSIFSR_RDF, 0);
rz_ssi_reg_mask_setl(ssi, SSIFSR, SSIFSR_RDF, 0);