Re: [PATCH 2/3] clk: shmobile: Add MSTP clock support

[Laurent Pinchart <laurent.pinchart@ideasonboard.com>]

Hi Kumar,

Thank you for the review.

On Tuesday 29 October 2013 18:36:06 Kumar Gala wrote:
> On Oct 29, 2013, at 9:55 AM, Laurent Pinchart wrote:
> > MSTP clocks are gate clocks controlled through a register that handles
> > up to 32 clocks. The register is often sparsely populated.
> > 
> > Those clocks are found on Renesas ARM SoCs.
> > 
> > Signed-off-by: Laurent Pinchart
> > <laurent.pinchart+renesas@ideasonboard.com>
> > ---
> > .../bindings/clock/renesas,cpg-mstp-clocks.txt     |  47 +++++
> > drivers/clk/shmobile/Makefile                      |   1 +
> > drivers/clk/shmobile/clk-mstp.c                    | 229 +++++++++++++++++
> > include/dt-bindings/clock/r8a7790-clock.h          |  56 +++++
> > 4 files changed, 333 insertions(+)
> > create mode 100644
> > Documentation/devicetree/bindings/clock/renesas,cpg-mstp-clocks.txt
> > create mode 100644 drivers/clk/shmobile/clk-mstp.c
> > create mode 100644 include/dt-bindings/clock/r8a7790-clock.h
> > 
> > diff --git
> > a/Documentation/devicetree/bindings/clock/renesas,cpg-mstp-clocks.txt
> > b/Documentation/devicetree/bindings/clock/renesas,cpg-mstp-clocks.txt new
> > file mode 100644
> > index 0000000..b3a1ce0
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/clock/renesas,cpg-mstp-clocks.txt
> > @@ -0,0 +1,47 @@
> > +* Renesas R8A7790 MSTP Clocks
> 
> can we spell out MSTP once in the heading?

Sure thing. It stands for Module Stop.

> > +
> > +The CPG can gate SoC device clocks. The gates are organized in groups of
> > up to
> > +32 gates.
> > +
> > +This device tree binding describes a single 32 gate clocks group per
> > node.
> > +Clocks are referenced by user nodes by the MSTP node phandle and the
> > clock
> > +index in the group, from 0 to 31.
> > +
> > +Required Properties:
> > +
> > +  - compatible: Must be one of the following
> > +    - "renesas,r8a7790-mstp-clocks" for R8A7790 (R-Car H2) MSTP gate
> > clocks
> > +    - "renesas,cpg-mstp-clock" for generic MSTP gate clocks
> > +  - reg: Base address and length of the memory resource used by the MSTP
> > +    clocks
> > +  - clocks: Reference to the parent clocks
> > +  - #clock-cells: Must be 1
> > +  - clock-output-names: The name of the clocks as free-form strings
> > +  - renesas,indices: Index of the gate clocks (0 to 31)
> 
> Index of the gate clock into what?

Into the 32 gates clock group. Groups have 32 entries with a 32-bit register 
that controls 32 gate clocks. The groups (and thus registers) are sparsly 
populated, this property lists the indices for the register bits corresponding 
to the clocks.

Would

  - renesas,indices: Indices of the gate clocks into the group (0 to 31)

be explicit enough ?

> > +
> > +The clocks, clock-output-names and renesas,indices properties contain one
> > +entry per gate. The MSTP groups are sparsely populated. Unimplemented
> > gates
> per gate clock. (?)

I'll change that.

> > +must not be declared.
> > +
> > +
> > +Example
> > +-------
> > +
> > +	#include <dt-bindings/clock/r8a7790-clock.h>
> > +
> > +	mstp3_clks: mstp3_clks {

mstp3_clks@e615013c I suppose.

> > +		compatible = "renesas,r8a7790-mstp-clocks", "renesas,cpg-mstp-
clocks";
> > +		reg = <0 0xe615013c 0 4>, <0 0xe6150048 0 4>;
> > +		clocks = <&cp_clk>, <&mmc1_clk>, <&sd3_clk>, <&sd2_clk>,
> > +			 <&cpg_clocks R8A7790_CLK_SD1>, <&cpg_clocks 
R8A7790_CLK_SD0>,
> > +			 <&mmc0_clk>;
> > +		#clock-cells = <1>;
> > +		clock-output-names > > +			"tpu0", "mmcif1", "sdhi3", "sdhi2",
> > +			 "sdhi1", "sdhi0", "mmcif0";
> > +		renesas,clock-indices = <
> > +			R8A7790_CLK_TPU0 R8A7790_CLK_MMCIF1 R8A7790_CLK_SDHI3
> > +			R8A7790_CLK_SDHI2 R8A7790_CLK_SDHI1 R8A7790_CLK_SDHI0
> > +			R8A7790_CLK_MMCIF0
> > +		>;
> > +	};

-- 
Regards,

Laurent Pinchart