Here is a proposal to extend the OPP bindings with bandwidth based on a previous discussion [1]. Every functional block on a SoC can contribute to the system power efficiency by expressing its own bandwidth needs (to memory or other SoC modules). This will allow the system to save power when high throughput is not required (and also provide maximum throughput when needed). There are at least three ways for a device to determine its bandwidth needs: 1. The device can dynamically calculate the needed bandwidth based on some known variable. For example: UART (baud rate), I2C (fast mode, high-speed mode, etc), USB (specification version, data transfer type), SDHC (SD standard, clock rate, bus-width), Video Encoder/Decoder (video format, resolution, frame-rate) 2. There is a hardware specific value. For example: hardware specific constant value (e.g. for PRNG) or use-case specific value that is hard-coded. 3. Predefined SoC/board specific bandwidth values. For example: CPU or GPU bandwidth is related to the current core frequency and both bandwidth and frequency are scaled together. This patchset is trying to address point 3 above by extending the OPP bindings to support predefined SoC/board bandwidth values and adds support in cpufreq-dt to scale the interconnect between the CPU and the DDR together with frequency and voltage. [1] https://patchwork.kernel.org/patch/10577315/ Changes in v2: * Added support for configuring multiple interconnect paths per each device and changed the way we describe it in DT. (Viresh) * Rename the DT property opp-bw-MBps to bandwidth-MBps. (Viresh) * Document MBps in property-units.txt. (Rob) * New patch to add of_icc_get_by_index() helper function. * Add _of_find_paths() to populate OPP tables with interconnect path data from DT. (Viresh) v1: https://lore.kernel.org/lkml/20190313090010.20534-1-georgi.djakov@xxxxxxxxxx/ Georgi Djakov (5): dt-bindings: opp: Introduce bandwidth-MBps bindings interconnect: Add of_icc_get_by_index() helper function OPP: Add support for parsing the interconnect bandwidth OPP: Update the bandwidth on OPP frequency changes cpufreq: dt: Add support for interconnect bandwidth scaling Documentation/devicetree/bindings/opp/opp.txt | 38 +++++++ .../devicetree/bindings/property-units.txt | 4 + drivers/cpufreq/cpufreq-dt.c | 27 ++++- drivers/interconnect/core.c | 45 ++++++-- drivers/opp/core.c | 96 ++++++++++++++++- drivers/opp/of.c | 102 ++++++++++++++++++ drivers/opp/opp.h | 9 ++ include/linux/interconnect.h | 6 ++ include/linux/pm_opp.h | 14 +++ 9 files changed, 327 insertions(+), 14 deletions(-)
