Re: [PATCH v2 1/2] Documentation: dt: add bindings for ti-cpufreq

Rob Herring
2016-09-19T21:14:00Z

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-l0cyMroinI0@public.gmane.org>
> ---
> 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.

> +
> +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.

Rob