linux-kernel - [PATCH 0/7] MIPS: ralink: add CPU clock detection and clock gate driver for MT7621

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Date:   Wed, 11 Nov 2020 17:30:06 +0100
From:   Sergio Paracuellos <sergio.paracuellos@...il.com>
To:     mturquette@...libre.com
Cc:     sboyd@...nel.org, robh+dt@...nel.org, tsbogend@...ha.franken.de,
        john@...ozen.org, gregkh@...uxfoundation.org, gch981213@...il.com,
        hackpascal@...il.com, jiaxun.yang@...goat.com,
        linux-clk@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-mips@...r.kernel.org,
        devel@...verdev.osuosl.org
Subject: [PATCH 0/7] MIPS: ralink: add CPU clock detection and clock gate driver for MT7621

This patchset ports CPU clock detection for MT7621 from OpenWrt
and adds a complete clock plan for the mt7621 SOC.

The documentation for this SOC only talks about two registers
regarding to the clocks:
* SYSC_REG_CPLL_CLKCFG0 - provides some information about boostrapped
refclock. PLL and dividers used for CPU and some sort of BUS (AHB?).
* SYSC_REG_CPLL_CLKCFG1 - a banch of gates to enable/disable clocks for
all or some ip cores. 

No documentation about a probably existant set of dividers for each ip
core is included in the datasheets. So we cannot make anything better,
AFAICT.

Looking into driver code, there is another frequency which is used in
some drivers (uart, sd...) which for any reason is always hardcoded to
50 MHz. Taking this into account this patchset provides three main fixed
clocks to the SOC in 'mt7621-pll' which are:
  - "cpu": with detected frequency (900 MHz in my board).
  - "ahb": cpu / 4 = 225 Mhz.
  - "apb": 50 Mhz.

PLL controller cannot be manipulatedbecause there is no info about
how to do it. Because of this, there is nothing related with registers
in the included binding.

It also provides a clock gate driver 'mt7621-clk' as a platform driver
to allow to enable and disable some clocks in the different ip cores.
The parent clocks for this clock gates have also set taking into account
existant device tree and driver code resulting in the followings:
  - "hsdma": "ahb"
  - "fe": "ahb"
  - "sp_divtx": "ahb"
  - "timer": "cpu"
  - "int": "cpu"
  - "mc": "ahb"
  - "pcm": "ahb"
  - "pio": "ahb"
  - "gdma": "ahb"
  - "nand": "ahb"
  - "i2c": "ahb"
  - "i2s": "ahb"
  - "spi": "ahb"
  - "uart1": "apb"
  - "uart2": "apb"
  - "uart3": "apb"
  - "eth": "ahb"
  - "pcie0": "ahb"
  - "pcie1": "ahb"
  - "pcie2": "ahb"
  - "crypto": "ahb"
  - "shxc": "ahb"

There was a previous attempt of doing this here[0] but the author
did not wanted to make assumptions of a clock plan for the platform.

I do really want this to be upstreamed so according to the comments
in previous attempt[0] from Oleksij Rempel I have tried to do this
by myself.

All of this patches have been tested in a GNUBee PC1 resulting in a
working platform.

[0]: https://www.lkml.org/lkml/2019/7/23/1044

Sergio Paracuellos (7):
  dt-bindings: clock: add dt binding header for mt7621 clocks
  dt: bindings: add mt7621-pll device tree binding documentation
  dt: bindings: add mt7621-clk device tree binding documentation
  MIPS: ralink: add clock device providing cpu/ahb/apb clock for mt7621
  clk: ralink: add clock gate driver for mt7621 SoC
  staging: mt7621-dts: make use of new 'mt7621-pll' and 'mt7621-clk'
  MAINTAINERS: add MT7621 CLOCK maintainer

 .../bindings/clock/mediatek,mt7621-clk.yaml   |  52 ++++
 .../bindings/clock/mediatek,mt7621-pll.yaml   |  51 ++++
 MAINTAINERS                                   |   8 +
 arch/mips/include/asm/mach-ralink/mt7621.h    |  20 ++
 arch/mips/ralink/mt7621.c                     |  87 ++++++
 drivers/clk/Kconfig                           |   1 +
 drivers/clk/Makefile                          |   1 +
 drivers/clk/ralink/Kconfig                    |  14 +
 drivers/clk/ralink/Makefile                   |   2 +
 drivers/clk/ralink/clk-mt7621.c               | 258 ++++++++++++++++++
 drivers/staging/mt7621-dts/gbpc1.dts          |  11 -
 drivers/staging/mt7621-dts/mt7621.dtsi        |  71 +++--
 include/dt-bindings/clock/mt7621-clk.h        |  39 +++
 13 files changed, 567 insertions(+), 48 deletions(-)
 create mode 100644 Documentation/devicetree/bindings/clock/mediatek,mt7621-clk.yaml
 create mode 100644 Documentation/devicetree/bindings/clock/mediatek,mt7621-pll.yaml
 create mode 100644 drivers/clk/ralink/Kconfig
 create mode 100644 drivers/clk/ralink/Makefile
 create mode 100644 drivers/clk/ralink/clk-mt7621.c
 create mode 100644 include/dt-bindings/clock/mt7621-clk.h

-- 
2.25.1