"[PATCH] NUC900: patch for implement clk_get_rate" https://lkml.org/lkml/2010/6/15/147 This patch would have fixed the apbfreq not being a real struct member and would also explain why clk_get_rate is called without using it's return value in the line above what you have. >From 2010, so it got dropped somewhere and ignored/abandoned