The DRAM controller allows to configure impedance either by using the
calibration against an external high precision 240 ohm resistor, or
by skipping the calibration and loading pre-defined data. The DRAM
controller register guide is available here:
http://linux-sunxi.org/A10_DRAM_Controller_Register_Guide#SDR_ZQCR0
The new code supports both of the impedance configuration modes:
- If the higher bits of the 'zq' parameter in the 'dram_para' struct
are zero, then the lowest 8 bits are used as the ZPROG value, where
two divisors encoded in lower and higher 4 bits. One divisor is
used for calibrating the termination impedance, and another is used
for the output impedance.
- If bits 27:8 in the 'zq' parameters are non-zero, then they are
used as the pre-defined ZDATA value instead of performing the ZQ
calibration.
Two lowest bits in the 'odt_en' parameter enable ODT for the DQ and DQS
lines individually. Enabling ODT for both DQ and DQS means that the
'odt_en' parameter needs to be set to 3.
Signed-off-by: Siarhei Siamashka <siarhei.siamashka@gmail.com>
Acked-by: Ian Campbell <ijc@hellion.org.uk>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
5c18384dea