Rob,
On 09/19/2016 04:14 PM, Rob Herring wrote:
On Wed, Aug 31, 2016 at 09:53:27PM -0500, Dave Gerlach wrote:
Add the device tree bindings document for the TI CPUFreq/OPP driver
on AM33xx, AM43xx, DRA7, and AM57 SoCs. The operating-points-v2 binding
allows us to provide an opp-supported-hw property for each OPP to define
when it is available. This driver is responsible for reading and parsing
registers to determine which OPPs can be selectively enabled based
on the specific SoC in use by matching against the opp-supported-hw
data.
Sorry, for the delay. Missed this somehow.
Signed-off-by: Dave Gerlach <d-gerlach@xxxxxx>
---
v1->v2:
- Dropped all driver/linux specific documentation
- Fixed some typos
- Add new compatibles for each SoC family to match against
- Switched to use am335x example to better demonstrate field one of
opp-supported-hw.
.../devicetree/bindings/cpufreq/ti-cpufreq.txt | 130 +++++++++++++++++++++
1 file changed, 130 insertions(+)
create mode 100644 Documentation/devicetree/bindings/cpufreq/ti-cpufreq.txt
diff --git a/Documentation/devicetree/bindings/cpufreq/ti-cpufreq.txt b/Documentation/devicetree/bindings/cpufreq/ti-cpufreq.txt
new file mode 100644
index 000000000000..6276ae494121
--- /dev/null
+++ b/Documentation/devicetree/bindings/cpufreq/ti-cpufreq.txt
@@ -0,0 +1,130 @@
+TI CPUFreq and OPP bindings
+================================
+
+Certain TI SoCs, like those in the am335x, am437x, am57xx, and dra7xx
+families support different OPPs depending on the silicon variant in use.
+The ti_cpufreq driver can use revision and an efuse value from the SoC to
+provide the OPP framework with supported hardware information. This is
+used to determine which OPPs from the operating-points-v2 table get enabled
+when it is parsed by the OPP framework.
+
+Required properties:
+--------------------
+In 'cpus' nodes:
+- operating-points-v2: Phandle to the operating-points-v2 table to use.
+- ti,syscon-efuse: Syscon phandle, offset to efuse register, efuse register
+ mask, and efuse register shift to get the relevant bits
+ that describe OPP availability.
+- ti,syscon-rev: Syscon and offset used to look up revision value on SoC.
These have nothing to do with a cpu, so they don't belong here. Maybe
the first is a property of an OPP table, but the second certainly is
not.
Yes, I have no issue with this and will move the ti properties into the
operating points table for v3 of the series.
+
+In 'operating-points-v2' table:
+- compatible: Should be
+ - 'operating-points-v2-ti-am3352-cpu' for am335x SoCs
+ - 'operating-points-v2-ti-am4372-cpu' for am43xx SoCs
+ - 'operating-points-v2-ti-dra7-cpu' for dra7xx/am57xx SoCs
+
+- opp-supported-hw: Two bitfields indicating:
+ 1. Which revision of the SoC the OPP is supported by
+ 2. Which eFuse bits indicate this OPP is available
I tend to think you should handle this with kernel code (bootloader
really) fixing up the OPP table as necessary rather than putting in DT.
The operating-points-v2 binding here [1] was designed with doing this in
mind, and others are using it and the corresponding functionality
offered by the OPP core to selectively enable OPPs. Why hide this in
u-boot when we already have kernel framework support to do it?
Thanks for your comments, will send v3 moving the appropriate properties
into the OPP table.
Regards,
Dave
[1] Documentation/devicetree/bindings/opp/opp.txt
Rob
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