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Re: [PATCH 02/48] ARM: at91: Document new TCB bindings

Started byRob Herring <robh@kernel.org>
First post2016-06-14 23:50 +0200
Last post2016-06-21 22:50 +0200
Articles 4 — 2 participants

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  Re: [PATCH 02/48] ARM: at91: Document new TCB bindings Rob Herring <robh@kernel.org> - 2016-06-14 23:50 +0200
    Re: [PATCH 02/48] ARM: at91: Document new TCB bindings Boris Brezillon <boris.brezillon@free-electrons.com> - 2016-06-15 09:40 +0200
      Re: [PATCH 02/48] ARM: at91: Document new TCB bindings Rob Herring <robh@kernel.org> - 2016-06-21 22:10 +0200
      Re: [PATCH 02/48] ARM: at91: Document new TCB bindings Rob Herring <robh@kernel.org> - 2016-06-21 22:50 +0200

#1422364 — Re: [PATCH 02/48] ARM: at91: Document new TCB bindings

FromRob Herring <robh@kernel.org>
Date2016-06-14 23:50 +0200
SubjectRe: [PATCH 02/48] ARM: at91: Document new TCB bindings
Message-ID<rK4nD-20k-1@gated-at.bofh.it>
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@linaro.org>
> Cc: Thierry Reding <thierry.reding@gmail.com>
> Cc: linux-pwm@vger.kernel.org
> Cc: Rob Herring <robh+dt@kernel.org>
> Cc: devicetree@vger.kernel.org
> Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
> ---
>  .../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.

> +   - 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.

>  - #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
>

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#1422708

FromBoris Brezillon <boris.brezillon@free-electrons.com>
Date2016-06-15 09:40 +0200
Message-ID<rKdAD-80i-63@gated-at.bofh.it>
In reply to#1422364
On Tue, 14 Jun 2016 16:47:37 -0500
Rob Herring <robh@kernel.org> 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@linaro.org>
> > Cc: Thierry Reding <thierry.reding@gmail.com>
> > Cc: linux-pwm@vger.kernel.org
> > Cc: Rob Herring <robh+dt@kernel.org>
> > Cc: devicetree@vger.kernel.org
> > Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
> > ---
> >  .../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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#1428129

FromRob Herring <robh@kernel.org>
Date2016-06-21 22:10 +0200
Message-ID<rMA9H-22L-13@gated-at.bofh.it>
In reply to#1422708
On Wed, Jun 15, 2016 at 09:29:55AM +0200, Boris Brezillon wrote:
> On Tue, 14 Jun 2016 16:47:37 -0500
> Rob Herring <robh@kernel.org> 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@linaro.org>
> > > Cc: Thierry Reding <thierry.reding@gmail.com>
> > > Cc: linux-pwm@vger.kernel.org
> > > Cc: Rob Herring <robh+dt@kernel.org>
> > > Cc: devicetree@vger.kernel.org
> > > Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
> > > ---
> > >  .../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?

If that somehow matches the documentation or accurately describes the 
h/w capabilities for them, then yes.

Rob

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#1428145

FromRob Herring <robh@kernel.org>
Date2016-06-21 22:50 +0200
Message-ID<rMAMp-2gO-5@gated-at.bofh.it>
In reply to#1422708
On Wed, Jun 15, 2016 at 09:29:55AM +0200, Boris Brezillon wrote:
> On Tue, 14 Jun 2016 16:47:37 -0500
> Rob Herring <robh@kernel.org> 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@linaro.org>
> > > Cc: Thierry Reding <thierry.reding@gmail.com>
> > > Cc: linux-pwm@vger.kernel.org
> > > Cc: Rob Herring <robh+dt@kernel.org>
> > > Cc: devicetree@vger.kernel.org
> > > Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
> > > ---
> > >  .../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/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?

Missed this in my first reply. I guess for purposes of referencing pwm 
from other nodes this is okay.

Rob

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