tRRD is specified in _TechnologyTimings, so we cannot specify different values for different speed grades. In the datasheet it depends on the speed grade, the highest possible value is used in the module definition. Should we move tRRD to _SpeedgradeTimings and define a specific value for each speedgrade?
From https://github.com/enjoy-digital/litedram/pull/181:
tRRDis specified in_TechnologyTimings, so we cannot specify different values for different speed grades. In the datasheet it depends on the speed grade, the highest possible value is used in the module definition. Should we movetRRDto_SpeedgradeTimingsand define a specific value for each speedgrade?