mirror of
https://xff.cz/git/u-boot/
synced 2026-04-12 00:20:01 +02:00
075d0b81e8
Alternate SDRAM DDR autocalibration routine that can be generically used for any PPC4xx chips that have the IBM SDRAM Controller core allowing for support of more DIMM/memory chip vendors and gets the DDR autocalibration values which give the best read latency performance (SDRAM0_RDCC.[RDSS]). Two alternate SDRAM DDR autocalibration algoritm are provided in this patch, "Method_A" and "Method_B". DDR autocalibration Method_A scans the full range of possible PPC4xx SDRAM Controller DDR autocalibration values and takes a lot longer to run than Method_B. Method_B executes in the same amount of time as the currently existing DDR autocalibration routine, i.e. 1 second or so. Normally Method_B is used and it is set as the default method. The current U-Boot PPC4xx DDR autocalibration code calibrates the IBM SDRAM Controller registers.[bit-field]: 1) SDRAM0_RQDC.[RQFD] 2) SDRAM0_RFDC.[RFFD] This alternate PPC4xx DDR autocalibration code calibrates the following IBM SDRAM Controller registers.[bit-field]: 1) SDRAM0_WRDTR.[WDTR] 2) SDRAM0_CLKTR.[CKTR] 3) SDRAM0_RQDC.[RQFD] 4) SDRAM0_RFDC.[RFFD] and will also use the calibrated settings of the above four registers that produce the best "Read Sample Cycle Select" value in the SDRAM0_RDCC.[RDSS] register.[bit-field]. Signed-off-by: Adam Graham <agraham@amcc.com> Signed-off-by: Stefan Roese <sr@denx.de>