According to eDP spec, sink can required specific selective update granularity that source must comply. Here caching the value if required and checking if source supports it. v3: - Returning the default granularity in case DPCD read fails(Dhinakaran) - Changed DPCD error message level(Dhinakaran) v4: - Setting granularity to defaul when granularity read is equal to 0(Dhinakaran) Cc: Rodrigo Vivi <rodrigo.vivi@intel.com> Cc: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com> Signed-off-by: José Roberto de Souza <jose.souza@intel.com> Reviewed-by: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com> Link: https://patchwork.freedesktop.org/patch/msgid/20181204003403.23361-9-jose.souza@intel.com