The hardware DQS gate training is a bit unreliable and does not
always find the best delay settings.
So we introduce a 32-bit 'dqs_gating_delay' variable, where each
byte encodes the DQS gating delay for each byte lane. The delay
granularity is 1/4 cycle.
Also we allow to enable the active DQS gating window mode, which
works better than the passive mode in practice. The DDR3 spec
says that there is a 0.9 cycles preamble and 0.3 cycle postamble.
The DQS window has to be opened during preamble and closed during
postamble. In the passive window mode, the gating window is opened
and closed by just using the gating delay settings. And because
of the 1/4 cycle delay granularity, accurately hitting the 0.3
cycle long postamble is a bit tough. In the active window mode,
the gating window is auto-closing with the help of monitoring
the DQS line, which relaxes the gating delay accuracy requirements.
But the hardware DQS gate training is still performed in the passive
window mode. It is a more strict test, which is reducing the results
variance compared to the training with active window mode.
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>
It is going to be useful in more than one place.
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>
The stale error status should be cleared for all sun4i/sun5i/sun7i
hardware and not just for sun7i. Also there are two types of DQS
gate training errors ("found no result" and "found more than one
possible result"). Both are handled now.
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>
The sun5i hardware (Allwinner A13) introduced configurable MBUS clock
speed. Allwinner A13 uses only 16-bit data bus width to connect the
external DRAM, which is halved compared to the 32-bit data bus of sun4i
(Allwinner A10), so it does not make much sense to clock a wider
internal bus at a very high speed. The Allwinner A13 manual specifies
300 MHz MBUS clock speed limit and 533 MHz DRAM clock speed limit. Newer
sun7i hardware (Allwinner A20) has a full width 32-bit external memory
interface again, but still keeps the MBUS clock speed configurable.
Clocking MBUS too low inhibits memory performance and one has to find
the optimal MBUS/DRAM clock speed ratio, which may depend on many
factors:
http://linux-sunxi.org/A10_DRAM_Controller_Performance
This patch introduces a new 'mbus_clock' parameter for the 'dram_para'
struct and uses it as a desired MBUS clock speed target. If 'mbus_clock'
is not set, 300 MHz is used by default to match the older hardcoded
settings.
PLL5P and PLL6 are both evaluated as possible clock sources. Preferring
the one, which can provide higher clock frequency that is lower or
equal to the 'mbus_clock' target. In the case of a tie, PLL5P has
higher priority.
Attempting to set the MBUS clock speed has no effect on sun4i, but does
no harm either.
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>
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>
This patch adds DRAM initialisation support for the Allwinner A20 (sun7i)
processor. This code will not been compiled until the build is hooked up in a
later patch. It has been split out to keep the patches manageable.
Signed-off-by: Alexandru Gagniuc <mr.nuke.me@gmail.com>
Signed-off-by: Emilio López <emilio@elopez.com.ar>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Henrik Nordstrom <henrik@henriknordstrom.net>
Signed-off-by: Jens Kuske <jenskuske@gmail.com>
Signed-off-by: Luke Leighton <lkcl@lkcl.net>
Signed-off-by: Oliver Schinagl <oliver@schinagl.nl>
Signed-off-by: Siarhei Siamashka <siarhei.siamashka@gmail.com>
Signed-off-by: Stefan Roese <sr@denx.de>
Signed-off-by: Ian Campbell <ijc@hellion.org.uk>
Reviewed-by: Marek Vasut <marex@denx.de>
Cc: Tom Cubie <Mr.hipboi@gmail.com>
Reviewed-by: Tom Rini <trini@ti.com>
