Hi Saravana,
On 08/02/2018 03:57 AM, Saravana Kannan wrote:
> This driver registers itself as a devfreq device that allows devfreq
> governors to make bandwidth votes for an interconnect path. This allows
> applying various policies for different interconnect paths using devfreq
> governors.
>
> Example uses:
> * Use the devfreq performance governor to set the CPU to DDR interconnect
> path for maximum performance.
> * Use the devfreq performance governor to set the GPU to DDR interconnect
> path for maximum performance.
> * Use the CPU frequency to device frequency mapping governor to scale the
> DDR frequency based on the needs of the CPUs' current frequency.
Usually CPUs and GPUs have dedicated cpufreq/devfreq drivers and i was
wondering if the interconnect support could be put into these drivers
directly?
>
> Signed-off-by: Saravana Kannan <skannan@xxxxxxxxxxxxxx>
> ---
> Documentation/devicetree/bindings/devfreq/icbw.txt | 21 ++++
> drivers/devfreq/Kconfig | 13 +++
> drivers/devfreq/Makefile | 1 +
> drivers/devfreq/devfreq_icbw.c | 116 +++++++++++++++++++++
> 4 files changed, 151 insertions(+)
> create mode 100644 Documentation/devicetree/bindings/devfreq/icbw.txt
> create mode 100644 drivers/devfreq/devfreq_icbw.c
>
> diff --git a/Documentation/devicetree/bindings/devfreq/icbw.txt b/Documentation/devicetree/bindings/devfreq/icbw.txt
> new file mode 100644
> index 0000000..36cf045
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/devfreq/icbw.txt
> @@ -0,0 +1,21 @@
> +Interconnect bandwidth device
> +
> +icbw is a device that represents an interconnect path that connects two
> +devices. This device is typically used to vote for BW requirements between
> +two devices. Eg: CPU to DDR, GPU to DDR, etc
> +
> +Required properties:
> +- compatible: Must be "devfreq-icbw"
> +- interconnects: Pairs of phandles and interconnect provider specifier
> + to denote the edge source and destination ports of
> + the interconnect path. See also:
> + Documentation/devicetree/bindings/interconnect/interconnect.txt
> +- interconnect-names: Must have one entry with the name "path".
> +
> +Example:
> +
> + qcom,cpubw {
> + compatible = "devfreq-icbw";
> + interconnects = <&snoc MASTER_APSS_1 &bimc SLAVE_EBI_CH0>;
> + interconnect-names = "path";
interconnect-names is optional when there is only a single path.
> + };
> diff --git a/drivers/devfreq/Kconfig b/drivers/devfreq/Kconfig
> index 3d9ae68..590370e 100644
> --- a/drivers/devfreq/Kconfig
> +++ b/drivers/devfreq/Kconfig
> @@ -121,6 +121,19 @@ config ARM_RK3399_DMC_DEVFREQ
> It sets the frequency for the memory controller and reads the usage counts
> from hardware.
>
> +config DEVFREQ_ICBW
> + bool "DEVFREQ device for making bandwidth votes on interconnect paths"
Can this be a module?
> + select DEVFREQ_GOV_PERFORMANCE
> + select DEVFREQ_GOV_POWERSAVE
> + select DEVFREQ_GOV_USERSPACE
> + default n
There's no need to specify this default. It is 'n' by default anyway.
Also maybe you want to add something like:
depends on INTERCONNECT=y
Thanks,
Georgi
> + help
> + Different devfreq governors use this devfreq device to make
> + bandwidth votes for interconnect paths between different devices
> + (Eg: CPU to DDR, GPU to DDR, etc). This driver provides a generic
> + interface so that the devfreq governors can be shared across SoCs
> + and architectures.
> +
> source "drivers/devfreq/event/Kconfig"
