DDR DVFS tuning has found that several power-saving features don't have
good tradeoffs at higher frequencies -- at higher frequencies, we'll see
glitches or other errors. Provide tuning controls so these can be
disabled at higher OPPs, and left active only at the lower ones.
Signed-off-by: Brian Norris <briannorris@chromium.org>
Reviewed-by: Rob Herring <robh@kernel.org>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>
It's inefficient to use the same number of cycles for all OPPs, since
lower frequencies make for longer idle times. Let's specify the idle
time instead, so software can pick the optimal number of cycles on its
own.
NB: these bindings aren't used anywhere yet.
Signed-off-by: Brian Norris <briannorris@chromium.org>
Reviewed-by: Rob Herring <robh@kernel.org>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>
The driver and all downstream device trees [1] are using Hz units, but
the document claims MHz. DRAM frequency for these systems can't possibly
exceed 2^32-1 Hz, so the choice of unit doesn't really matter than much.
Rather than add unnecessary risk in getting the units wrong, let's just
go with the unofficial convention and make the docs match reality.
A sub-1MHz frequency is extremely unlikely, so include a minimum in the
schema, to help catch anybody who might have believed this was MHz.
[1] And notably, also those trying to upstream them:
https://lore.kernel.org/lkml/20210308233858.24741-3-daniel.lezcano@linaro.org/
Signed-off-by: Brian Norris <briannorris@chromium.org>
Reviewed-by: Rob Herring <robh@kernel.org>
Acked-by: Chanwoo Choi <cw00.choi@samsung.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>
These DRAM configuration properties are all handled in ARM Trusted
Firmware (and have been since the early days of this SoC), and there are
no in-tree users of the DMC binding yet. It's better to just defer to
firmware instead of maintaining this large list of properties.
There's also some confusion about units: many of these are specified in
MHz, but the downstream users and driver code are treating them as Hz, I
believe. Rather than straighten all that out, I just drop them.
Signed-off-by: Brian Norris <briannorris@chromium.org>
Reviewed-by: Rob Herring <robh@kernel.org>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>
I want to add, deprecate, and bugfix some properties, as well as add the
first users. This is easier with a proper schema.
The transformation is mostly straightforward, plus a few notable tweaks:
* Renamed rockchip,dram_speed_bin to rockchip,ddr3_speed_bin. The
driver code and the example matched, but the description was
different. I went with the implementation. Note that this property is
also slated for deprecation/deletion in the subsequent patches.
* Drop upthreshold and downdifferential properties from the example.
These were undocumented (so, wouldn't pass validation), but were
representing software properties (governor tweaks). I drop them from
the driver in subsequent patches.
* Rename clock from pclk_ddr_mon to dmc_clk. The driver, DT example,
and all downstream users matched -- the binding definition was the
exception. Anyway, "dmc_clk" is a more appropriately generic name.
* Choose a better filename and location (this is a memory controller).
Signed-off-by: Brian Norris <briannorris@chromium.org>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>
