[U-Boot] DDR2 driver strength and ODT on FSL 85xx

[U-Boot] DDR2 driver strength and ODT on FSL 85xx

[Felix Radensky]

Hi,

I'm working on a custom board based on FSL P1011. The board has 128MB of 
soldered
DDR2 connected to a single chip select. Simulation results indicate that 
better DDR2
behavior would be achieved by using half strength DDR drivers. The 
driver strength
on P1011 is controlled by DDR_SDRAM_CFG[HSE] and various fields in 
DDR_CDR_1.
I also need to configure DDR ODT, which is controlled by  DDR_CDR_2 
register.

The problem is that  DDR setup code for P1020/P1011 does not configure 
DDR_CDR_X
registers. I was tempted to add them to struct fsl_ddr_cfg_regs_s, and 
modify
fsl_ddr_set_memctl_regs() in ddr_gen2.c to deal with them, but noticed 
that on some 85XX
SoC (e.g. MPC8548), there's a single DDR_CDR register, which is not part 
of DDR CCSR
space. Which means that current definition of  struct ccsr_ddr in 
immap_85xx.h is not
correct for these SoCs.

How would you suggest to solve my problem in a generic way ?

Thanks.

Felix.