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authorNicola Corna <nicola@corna.info>2016-11-16 08:57:15 +0100
committerMartin Roth <martinroth@google.com>2016-12-27 18:18:04 +0100
commit76f8dbc4f70469e0b5913796d6130e85df1cdd77 (patch)
treee28af65fa0a0c8134840d2de087b96dfa0794fae /src/mainboard
parentaa5c8f78f98614130cfb4802faa30b6a6b92e815 (diff)
device/dram/ddr3: add FTB timings
SPD revision 1.1 introduced FTB timings, an extra set of SPD values that specify a more precise tCKmin, tAAmin, tRCDmin, tRPmin and tRCmin. For backwards compatibility, the MTB is usually rounded up and the FTB part is negative. For this reason some memories were not set up optimally, as the FTB part was ignored and the resulting timing wasn't set to the minimum value. The tests were performed on a Lenovo X220 with two Micron 8KTF51264HZ-1G9E (1866 MHz): reading only the MTB part, coreboot reports a tCKmin of 1.125 ns, corresponding to a working frequency of 800 MHz; with the additional tCKmin FTB part (-0.054 ns) the new (rounded) value is 1.070 ns, valid for a 933 MHz operation. Tested also with Ballistix DDR3-1866 SODIMM on Lenovo T420: the memory is now detected as DDR3-1866 instead of DDR3-1600. Some manufacturers (like Micron) seems to expect a small rounding on the timings, so a nearest-value rounding is performed. If this assumption isn't correct, an error up to ~2 ps can be committed, which is low enough to be safely ignored. Change-Id: Ib98f2e70820f207429d04ca6421680109a81f457 Signed-off-by: Nicola Corna <nicola@corna.info> Reviewed-on: https://review.coreboot.org/17476 Tested-by: build bot (Jenkins) Reviewed-by: Patrick Rudolph <siro@das-labor.org> Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
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