By handling latency variable efficiently we also get rid of this warning :
CC [M] drivers/gpu/drm/i915/intel_display.o
drivers/gpu/drm/i915/intel_display.c: In function ‘igd_enable_cxsr’:
drivers/gpu/drm/i915/intel_display.c:1918: warning: ‘latency’ may be used uninitialized in this function