On Tue, 14 Jun 2016 16:47:37 -0500
Rob Herring [off-list ref] wrote:

On Sat, Jun 11, 2016 at 12:03:05AM +0200, Alexandre Belloni wrote:

quoted

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 <redacted>
Cc: Thierry Reding <redacted>
Cc: linux-pwm@vger.kernel.org
Cc: Rob Herring <robh+dt@kernel.org>
Cc: devicetree@vger.kernel.org
Signed-off-by: Alexandre Belloni <redacted>
---
 .../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  

[...]

quoted

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?

quoted

+
+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?

quoted

+   - 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

quoted

+
+		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?

quoted

 - #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