On Thu, Oct 17, 2013 at 04:35:38PM +0530, SRICHARAN R wrote:
The change from 0x64656465 to 0x64646464 is to remove the weak pull enabled on DQS, nDQS lines. This pulls the differential signals in the same direction which is not intended. So disabling the weak pulls improves signal integrity.
On the uEVM there are 4 DDR3 devices. The VREF for 2 of the devices is powered by the OMAP's VREF_CA_OUT pins. The VREF on the other 2 devices is powered by the OMAP's VREF_DQ_OUT pins. So the net effect here is that only half of the DDR3 devices were being supplied a VREF! This was clearly a mistake. The second change improves the robustness of the interface and was specifically seen to cure corruption observed at high temperatures on some boards.
With the above two changes better memory stability was observed with extended temperature ranges around 100C.
Signed-off-by: Sricharan R r.sricharan@ti.com
Applied to u-boot-ti/master, thanks!