On Tue, 14 Jun 2016 16:47:37 -0500
Rob Herring <robh@xxxxxxxxxx> wrote:
> On Sat, Jun 11, 2016 at 12:03:05AM +0200, Alexandre Belloni wrote:
> > The current binding for the TCB is not flexible enough for some use cases
> > and prevents proper utilization of all the channels.
> >
> > Cc: Daniel Lezcano <daniel.lezcano@xxxxxxxxxx>
> > Cc: Thierry Reding <thierry.reding@xxxxxxxxx>
> > Cc: linux-pwm@xxxxxxxxxxxxxxx
> > Cc: Rob Herring <robh+dt@xxxxxxxxxx>
> > Cc: devicetree@xxxxxxxxxxxxxxx
> > Signed-off-by: Alexandre Belloni <alexandre.belloni@xxxxxxxxxxxxxxxxxx>
> > ---
> > .../devicetree/bindings/arm/atmel-at91.txt | 32 -----------
> > .../devicetree/bindings/mfd/atmel-tcb.txt | 62 ++++++++++++++++++++++
> > .../devicetree/bindings/pwm/atmel-tcb-pwm.txt | 12 +++--
> > 3 files changed, 69 insertions(+), 37 deletions(-)
> > create mode 100644 Documentation/devicetree/bindings/mfd/atmel-tcb.txt
>
> [...]
>
> > diff --git a/Documentation/devicetree/bindings/mfd/atmel-tcb.txt b/Documentation/devicetree/bindings/mfd/atmel-tcb.txt
> > new file mode 100644
> > index 000000000000..48196752c78f
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/mfd/atmel-tcb.txt
> > @@ -0,0 +1,62 @@
> > +* Device tree bindings for Atmel Timer Counter Blocks
> > +- compatible: Should be "atmel,<chip>-tcb", "simple-mfd", "syscon".
> > + <chip> can be "at91rm9200" or "at91sam9x5"
> > +- reg: Should contain registers location and length
> > +- #address-cells: has to be 1
> > +- #size-cells: has to be 0
> > +- interrupts: Should contain all interrupts for the TC block
> > + Note that you can specify several interrupt cells if the TC
> > + block has one interrupt per channel.
> > +- clock-names: tuple listing input clock names.
> > + Required elements: "t0_clk", "slow_clk"
> > + Optional elements: "t1_clk", "t2_clk"
> > +- clocks: phandles to input clocks.
>
> What is the order of clocks?
>
> > +
> > +The TCB can expose multiple subdevices:
> > + * a clocksource and clockevent device
>
> No. These compatible names are linuxisms. Describe features of the
> timers to be able to select which timer to use if you need to pick
> certain timers. For example, interrupt capability could be used to
> select the clkevt.
Would 'atmel,tcb-free-running-timer' (to replace 'atmel,tcb-clksrc') and
'atmel,tcb-programmable-timer' (to replace 'atmel,tcb-clkevt') be
acceptable?
>
> > + - compatible: Should be "atmel,tcb-clksrc"
> > + - reg: Should contain the TCB channels to be used. If the
> > + counter width is 16 bits (at91rm9200-tcb), two consecutive
> > + channels are needed. Else, only one channel will be used.
> > +
> > + * a clockevent device
> > + - compatible: Should be "atmel,tcb-clkevt"
> > + - reg: Should contain the TCB channel to be used
> > +
> > + * a PWM chip: see ../pwm/atmel-tcb-pwm.txt
> > +
> > +Examples:
> > +
> > +One interrupt per TC block:
> > + tcb0: timer@fff7c000 {
> > + compatible = "atmel,at91rm9200-tcb", "simple-mfd", "syscon";
> > + #address-cells = <1>;
> > + #size-cells = <0>;
> > + reg = <0xfff7c000 0x100>;
> > + interrupts = <18 4>;
> > + clocks = <&tcb0_clk>;
> > + clock-names = "t0_clk";
>
> Missing slow_clk
>
> > +
> > + timer@0 {
> > + compatible = "atmel,tcb-clksrc";
> > + reg = <0>, <1>;
> > + };
> > +
> > + timer@2 {
> > + compatible = "atmel,tcb-clkevt";
> > + reg = <2>;
> > + };
> > + };
> > +
> > +One interrupt per TC channel in a TC block:
> > + tcb1: timer@fffdc000 {
> > + compatible = "atmel,at91rm9200-tcb", "simple-mfd", "syscon";
> > + #address-cells = <1>;
> > + #size-cells = <0>;
> > + reg = <0xfffdc000 0x100>;
> > + interrupts = <26 4>, <27 4>, <28 4>;
> > + clocks = <&tcb1_clk>;
> > + clock-names = "t0_clk";
> > + };
> > +
> > +
> > diff --git a/Documentation/devicetree/bindings/pwm/atmel-tcb-pwm.txt b/Documentation/devicetree/bindings/pwm/atmel-tcb-pwm.txt
> > index 8031148bcf85..ab8fbd5ba184 100644
> > --- a/Documentation/devicetree/bindings/pwm/atmel-tcb-pwm.txt
> > +++ b/Documentation/devicetree/bindings/pwm/atmel-tcb-pwm.txt
> > @@ -2,15 +2,17 @@ Atmel TCB PWM controller
> >
> > Required properties:
> > - compatible: should be "atmel,tcb-pwm"
> > +- reg: tcb channel to use. Each channel can export 2 PWMs
>
> Is there a difference in channels? If not, then this compatible should
> go.
This one I don't understand.
The TCB (Timer Counter Block) is an MFD containing 3 Timer Counter
devices. Each of these devices (also called channels) can be assigned a
specific mode:
- timer mode (free-running of programmable)
- waveform generator mode (IOW, a PWM)
- capture mode (an IIO device, but we don't have any driver for that
right now)
So each sub-device of the TCB is represented as a sub-node with its own
compatible. Is there a problem with that?
>
> > - #pwm-cells: should be 3. See pwm.txt in this directory for a description of
> > the cells format. The only third cell flag supported by this binding is
> > PWM_POLARITY_INVERTED.
> > -- tc-block: The Timer Counter block to use as a PWM chip.
> >
> > Example:
> >
> > -pwm {
> > - compatible = "atmel,tcb-pwm";
> > - #pwm-cells = <3>;
> > - tc-block = <1>;
> > +tcb0: timer@f800c000 {
> > + pwm@0 {
> > + compatible = "atmel,tcb-pwm";
> > + reg = <0>;
> > + #pwm-cells = <3>;
> > + };
> > };
> > --
> > 2.8.1
> >
--
Boris Brezillon, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com
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