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Commit 50581cc4 authored by Linus Walleij's avatar Linus Walleij Committed by Stephen Boyd
Browse files

clk: versatile add DT bindings for the ICST CM variants 



The Integrator/AP and Integrator/CP core modules have special
versions of the ICST525 interface hardcoding some bits. Create
special compatible strings to identify these variants, also
explain a bit what is going on.

Cc: devicetree@vger.kernel.org
Cc: Russell King <linux@armlinux.org.uk>
Signed-off-by: default avatarLinus Walleij <linus.walleij@linaro.org>
Acked-by: default avatarRob Herring <robh@kernel.org>
Signed-off-by: default avatarStephen Boyd <sboyd@codeaurora.org>
parent 62d15758

Documentation/devicetree/bindings/clock/arm-syscon-icst.txt

+32 −2
Original line number Diff line number Diff line
@@ -5,20 +5,50 @@ Technology (IDT). ARM integrated these oscillators deeply into their 
reference designs by adding special control registers that manage such

oscillators to their system controllers.



The ARM system controller contains logic to serialize and initialize

The various ARM system controllers contain logic to serialize and initialize

an ICST clock request after a write to the 32 bit register at an offset

into the system controller. Furthermore, to even be able to alter one of

these frequencies, the system controller must first be unlocked by

writing a special token to another offset in the system controller.



Some ARM hardware contain special versions of the serial interface that only

connects the low 8 bits of the VDW (missing one bit), hardwires RDW to

different values and sometimes also hardwire the output divider. They

therefore have special compatible strings as per this table (the OD value is

the value on the pins, not the resulting output divider):



Hardware variant:        RDW     OD          VDW



Integrator/AP            22      1           Bit 8 0, rest variable

integratorap-cm



Integrator/AP            46      3           Bit 8 0, rest variable

integratorap-sys



Integrator/AP            22 or   1           17 or (33 or 25 MHz)

integratorap-pci         14      1           14



Integrator/CP            22      variable    Bit 8 0, rest variable

integratorcp-cm-core



Integrator/CP            22      variable    Bit 8 0, rest variable

integratorcp-cm-mem



The ICST oscillator must be provided inside a system controller node.



Required properties:

- compatible: must be one of

  "arm,syscon-icst525"

  "arm,syscon-icst307"

  "arm,syscon-icst525-integratorap-cm"

  "arm,syscon-icst525-integratorap-sys"

  "arm,syscon-icst525-integratorap-pci"

  "arm,syscon-icst525-integratorcp-cm-core"

  "arm,syscon-icst525-integratorcp-cm-mem"

- lock-offset: the offset address into the system controller where the

  unlocking register is located

- vco-offset: the offset address into the system controller where the

  ICST control register is located (even 32 bit address)

- compatible: must be one of "arm,syscon-icst525" or "arm,syscon-icst307"

- #clock-cells: must be <0>

- clocks: parent clock, since the ICST needs a parent clock to derive its

  frequency from, this attribute is compulsory.