When changing the L3 clock frequency, the CPU is executing from internal RAM
and the SDRC clock is disabled. During this time accesses made to external
DDR are stalled. If the ARM subsystem attempts to access the DDR while the
SDRC clock is disabled this will stall the CPU until the access to the SDRC
timeouts. A timeout on the SDRC should never occur. Once a timeout occurs all
the following accesses will be aborted and the DDR is no longer accessible.
Although the code being executed in the internal RAM does not directly access
the DDR, it was found that the branch prediction logic in the CPU may cause
the CPU to prefetch code from a DDR location while the SDRC clock is disabled.
This was causing an SDRC timeout which resulted in a system hang.
This patch fixes this problem by ensuring the branch prediction logic is
disabled while changing the L3 clock frequency. The branch prediction logic
is disabled by clearing the Z-bit in the ARM CTRL register.
Disabling the branch prediction logic does not have any noticable impact
on the execution time of this code section. The hardware observability
signals were used to monitor the sdrc idle time with and without this
patch when operating at different CPU frequencies (150MHz, 500MHz and
600MHz) and the total sdrc idle time when changing frequenct was in
the range of 9-11us. This was measured on an omap3430 SDP running the
omapzoom p-android-omap-2.6.29 branch.
Signed-off-by: Jon Hunter <jon-hunter@ti.com>
Signed-off-by: Paul Walmsley <paul@pwsan.com>
Cc: Santosh Shilimkar <santosh.shilimkar@ti.com>
Cc: Richard Woodruff <r-woodruff2@ti.com>
Cc: Tony Lindgren <tony@atomide.com>
The code that reprograms the SDRC memory controller during CORE DVFS,
mach-omap2/sram34xx.S:omap3_sram_configure_core_dpll(), does not
ensure that all L3 initiators are prevented from accessing the SDRAM
before modifying the SDRC AC timing and MR registers. This can cause
memory to be corrupted or cause the SDRC to enter an unpredictable
state. This patch places that code behind a Kconfig option,
CONFIG_OMAP3_SDRC_AC_TIMING for now, and adds a note explaining what
is going on. Ideally the code can be added back in once supporting
code is present to ensure that other initiators aren't touching the
SDRAM. At the very least, these registers should be reprogrammable
during kernel init to deal with buggy bootloaders. Users who know
that all other system initiators will not be touching the SDRAM can
also re-enable this Kconfig option.
This is a modification of a patch originally written by Rajendra Nayak
<rnayak@ti.com> (the original is at http://patchwork.kernel.org/patch/51927/).
Rather than removing the code completely, this patch just comments it out.
Thanks to Benoît Cousson <b-cousson@ti.com> and Christophe Sucur
<c-sucur@ti.com> for explaining the technical basis for this and for
explaining what can be done to make this path work in future code.
Thanks to Richard Woodruff <r-woodruff2@ti.com>, Nishanth Menon
<nm@ti.com>, and Olof Johansson <olof@lixom.net> for their comments.
Signed-off-by: Paul Walmsley <paul@pwsan.com>
Cc: Rajendra Nayak <rnayak@ti.com>
Cc: Christophe Sucur <c-sucur@ti.com>
Cc: Benoît Cousson <b-cousson@ti.com>
Cc: Richard Woodruff <r-woodruff2@ti.com>
Cc: Nishanth Menon <nm@ti.com>
Cc: Olof Johansson <olof@lixom.net>
The clock stabilization delay post a M2 divider change is needed
even before a SDRC interface clock re-enable and not only before
jumping back to SDRAM.
Signed-off-by: Rajendra Nayak <rnayak@ti.com>
Signed-off-by: Paul Walmsley <paul@pwsan.com>
This patch fixes a bug in the CORE dpll scaling sequence which was
errouneously clearing some bits in the SDRC DLLA CTRL register and
hence causing a freeze. The issue was observed only on platforms
which scale CORE dpll to < 83Mhz and hence program the DLL in fixed
delay mode.
Issue reported by Limei Wang <E12499@motorola.com>, with debugging
assistance from Richard Woodruff <r-woodruff2@ti.com> and Girish
Ghongdemath <girishsg@ti.com>.
Signed-off-by: Rajendra Nayak <rnayak@ti.com>
Cc: Limei Wang <E12499@motorola.com>
Cc: Richard Woodruff <r-woodruff2@ti.com>
Cc: Girish Ghongdemath <girishsg@ti.com>
Signed-off-by: Paul Walmsley <paul@pwsan.com>
[paul@pwsan.com: updated patch description to include collaboration credits]
Stop setting SDRC_POWER.PWDENA on boot. There is a nasty erratum
(34xx erratum 1.150) that can cause memory corruption if PWDENA is
enabled.
Based originally on a patch from Samu P. Onkalo <samu.p.onkalo@nokia.com>.
Tested on BeagleBoard rev C2.
Signed-off-by: Paul Walmsley <paul@pwsan.com>
Cc: Samu P. Onkalo <samu.p.onkalo@nokia.com>
Some OMAP3 boards (Beagle Cx, Overo, RX51, Pandora) have 2
SDRAM parts connected to the SDRC.
This patch adds the following:
- add a new argument of type omap_sdrc_params struct*
to omap2_init_common_hw and omap2_sdrc_init for the 2nd CS params
- adapted the OMAP boards files to the new prototype of
omap2_init_common_hw
- add the SDRC 2nd CS registers offsets defines
- adapt the sram sleep code to configure the SDRC for the 2nd CS
Note: If the 2nd param to omap2_init_common_hw is NULL, then the
parameters are not programmed into the SDRC CS1 registers
Tested on 3430 SDP and Beagleboard rev C2 and B5, with
suspend/resume and frequency changes (cpufreq).
Signed-off-by: Jean Pihet <jpihet@mvista.com>
Signed-off-by: Paul Walmsley <paul@pwsan.com>
Correspondence with the TI OMAP hardware team indicates that
SDRC_DLLA_CTRL.FIXEDDELAY should be initialized to 0x0f. This number
was apparently derived from process validation. This is only used
when the SDRC DLL is unlocked (e.g., SDRC clock frequency less than
83MHz).
Signed-off-by: Paul Walmsley <paul@pwsan.com>
Program the SDRC_MR_0 register as well during SDRC clock changes.
This register allows selection of the memory CAS latency. Some SDRAM
chips, such as the Qimonda HYB18M512160AF6, have a lower CAS latency
at lower clock rates.
Signed-off-by: Paul Walmsley <paul@pwsan.com>
When changing the SDRAM clock from 166MHz to 83MHz via the CORE DPLL M2
divider, add a short delay before returning to SDRAM to allow the SDRC
time to stabilize. Without this delay, the system is prone to random
panics upon re-entering SDRAM.
This time delay varies based on MPU frequency. At 500MHz MPU frequency at
room temperature, 64 loops seems to work okay; so add another 32 loops for
environmental and process variation.
Signed-off-by: Paul Walmsley <paul@pwsan.com>
The original CDP kernel that this code comes from waited for 0x800
loops after switching the CORE DPLL M2 divider. This does not appear
to be necessary.
Signed-off-by: Paul Walmsley <paul@pwsan.com>
According to the 34xx TRM Rev. K section 11.2.4.4.11.1 "Purpose of the
DLL/CDL Module," the SDRC delay-locked-loop can be locked at any SDRC
clock frequency from 83MHz to 166MHz. CDP code unconditionally
unlocked the DLL whenever shifting to a lower SDRC speed, but this
seems unnecessary and error-prone, as the DLL is no longer able to
compensate for process, voltage, and temperature variations. Instead,
only unlock the DLL when the SDRC clock rate would be less than 83MHz.
Signed-off-by: Paul Walmsley <paul@pwsan.com>
Renumber registers in omap3_sram_configure_core_dpll() assembly code to
make space for additional parameters.
Signed-off-by: Paul Walmsley <paul@pwsan.com>
Clear the SDRC_POWER.PWRENA bit before putting the SDRAM into self-refresh
mode. This prevents the SDRC from attempting to power off the SDRAM,
which can cause the system to hang.
Signed-off-by: Paul Walmsley <paul@pwsan.com>
Add more barriers in the SRAM CORE DPLL M2 divider change code.
- Add a DSB SY after the function's entry point to flush all cached
and buffered writes and wait for the interconnect to claim that they
have completed[1]. The idea here is to force all delayed write
traffic going to the SDRAM to at least post to the L3 interconnect
before continuing. If these writes are allowed to occur after the
SDRC is idled, the writes will not be acknowledged and the ARM will
stall.
Note that in this case, it does not matter if the writes actually
complete to the SDRAM - it is only necessary for the writes to leave
the ARM itself. If the writes are posted by the interconnect when
the SDRC goes into idle, the writes will be delayed until the SDRC
returns from idle[2]. If the SDRC is in the middle of a write when
it is requested to enter idle, the SDRC will not acknowledge the
idle request until the writes complete to the SDRAM.[3]
The old-style DMB in sdram_in_selfrefresh is now superfluous, so,
remove it.
- Add an ISB before the function's exit point to prevent the ARM from
speculatively executing into SDRAM before the SDRAM is enabled[4].
...
1. ARMv7 ARM (DDI 0406A) A3-47, A3-48.
2. Private communication with Richard Woodruff <r-woodruff2@ti.com>.
3. Private communication with Richard Woodruff <r-woodruff2@ti.com>.
4. ARMv7 ARM (DDI 0406A) A3-48.
Signed-off-by: Paul Walmsley <paul@pwsan.com>
Cc: Richard Woodruff <r-woodruff2@ti.com>
Add minimal omap3430 support based on earlier patches from
Syed Mohammed Khasim. Also merge in omap34xx SRAM support
from Karthik Dasu and use consistent naming for sram init
functions.
Also do following changes that make 34xx support usable:
- Remove unused sram.c functions for 34xx
- Rename IRQ_SIR_IRQ to INTCPS_SIR_IRQ and define it locally
in entry-macro.S
- Update mach-omap2/io.c to support 2420, 2430, and 34xx
- Also merge in 34xx GPMC changes to add fields wr_access and
wr_data_mux_bus from Adrian Hunter
- Remove memory initialization call omap2_init_memory() until
until more generic memory initialization patches are posted.
It's OK to rely on bootloader initialization until then.
Signed-off-by: Syed Mohammed, Khasim <khasim@ti.com>
Signed-off-by: Karthik Dasu<karthik-dp@ti.com>
Signed-off-by: Adrian Hunter <ext-adrian.hunter@nokia.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>
