Re: [RFC PATCH 1/3] arm/imx6: describe clocks in device tree source

[Sascha Hauer <s.hauer-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org>]

On Tue, Nov 22, 2011 at 09:48:54AM +0800, Shawn Guo wrote:
> It adds document for imx clock device tree bindings and then describes
> imx6 clocks in dts.
> 
> Signed-off-by: Shawn Guo <shawn.guo-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>
> ---
>  .../devicetree/bindings/clock/clock-imx.txt        |  124 +++
>  arch/arm/boot/dts/imx6q.dtsi                       |  943 +++++++++++++++++++-
>  2 files changed, 1058 insertions(+), 9 deletions(-)
>  create mode 100644 Documentation/devicetree/bindings/clock/clock-imx.txt
> 
> diff --git a/Documentation/devicetree/bindings/clock/clock-imx.txt b/Documentation/devicetree/bindings/clock/clock-imx.txt
> new file mode 100644
> index 0000000..5c597d9
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/clock/clock-imx.txt
> @@ -0,0 +1,124 @@
> +* Device Tree Bindings for Freescale i.MX Clock
> +
> +== Clock Gate ==
> +
> +Required properties:
> +- imx,clock-gate:  It's a two 32-bit integers array.  The first
> +  integer specifies the offset of the gate register, and the second
> +  one specifies the bit mask of the gate for this clock.

On i.MX53 we have two bit gates:

00b disable
01b disable in stop mode, enable in run mode
10b reserved
11b enable

I can't find this description in my i.MX6RM, but I suppose it's the same
here. Do you have plans for these? Currently only disable and enable
seem to be handled.


> +
> +		pll2_pfd_clk: pll2-pfd {
> +			compatible = "fsl,imx6q-pfd";
> +			#clock-cells = <3>;
> +			imx,clock-gate = <0x100 0x80>,
> +					 <0x100 0x8000>,
> +					 <0x100 0x800000>;
> +			imx,clock-divider = <0x100 0 0 0 6>,
> +					    <0x100 0 0 8 6>,
> +					    <0x100 0 0 16 6>;
> +			clock-input = <&pll_bus_clk 0>;
> +			clock-input-name = "pll2-bus";
> +			clock-output-name = "pll2-pfd-352m",
> +					    "pll2-pfd-594m",
> +					    "pll2-pfd-400m";
> +		};

Does this pll simultaneously have three different output frequencies?
I'm not familiar with the i.MX6 yet.

> +
> +		can_root_clk: can-root {
> +			compatible = "fsl,imx6q-clock";
> +			#clock-cells = <1>;
> +			imx,clock-divider = <0x20 0 0 2 6>;
> +			clock-input = <&pll_usb_clk 0 0>;
> +			clock-input-name = "pll3-usb-otg";
> +			clock-output-name = "can-root";
> +		};
> +
> +		can_clk: can {
> +			compatible = "fsl,imx6q-clock";
> +			#clock-cells = <4>;
> +			imx,clock-gate = <0x68 0xc000>,
> +					 <0x68 0x30000>,
> +					 <0x68 0xc0000>,
> +					 <0x68 0x300000>;
> +			clock-input = <&can_root_clk 0>;
> +			clock-input-name = "can-root";
> +			clock-output-name = "can1",
> +					    "can1-serial",
> +					    "can2",
> +					    "can2-serial";
> +		};
> +
> +		ecspi_root_clk: ecspi-root {
> +			compatible = "fsl,imx6q-clock";
> +			#clock-cells = <1>;
> +			imx,clock-divider = <0x38 0 0 19 6>;
> +			clock-input = <&pll3_div_clk 2 0 0>;
> +			clock-input-name = "pll3-60m";
> +			clock-output-name = "ecspi-root";
> +		};

I'm not sure you do yourself a favour if you skip all the muxes and
assume reset default for them. The ecspi-root parent is a mux The mux
seems to be missing in the can clock, uart and probably others.

> +
> +		ecspi_clk: ecspi {
> +			compatible = "fsl,imx6q-clock";
> +			#clock-cells = <5>;
> +			imx,clock-gate = <0x6c 0x3>,
> +					 <0x6c 0xc>,
> +					 <0x6c 0x30>,
> +					 <0x6c 0xc0>,
> +					 <0x6c 0x300>;
> +			clock-input = <&ecspi_root_clk 0>;
> +			clock-input-name = "ecspi-root";
> +			clock-output-name = "ecspi1",
> +					    "ecspi2",
> +					    "ecspi3",
> +					    "ecspi4",
> +					    "ecspi5";
> +		};
> +

[...]

> +
> +		uart_clk: uart {
> +			compatible = "fsl,imx6q-clock";
> +			#clock-cells = <2>;
> +			imx,clock-gate = <0x7c 0x3000000>,
> +					 <0x7c 0xc000000>;
> +			imx,clock-divider = <0x24 0 0 0 6>,
> +					    <0x24 0 0 0 6>;
> +			clock-input = <&pll3_div_clk 1 0 0>;
> +			clock-input-name = "pll3-80m";
> +			clock-output-name = "uart",
> +					    "uart-serial";
> +		};

This seems wrong. The UARTs have two clocks, the register clock and the
baud clock. parent of the baud clock is uart-root (the mux is missing
here) and parent of the register clock is the ipg clock. This node only
has one parent.

> +
> +		usboh3_clk: usboh3 {
> +			compatible = "fsl,imx6q-clock";
> +			#clock-cells = <1>;
> +			imx,clock-gate = <0x80 0x3>;
> +			clock-input = <&ipg_clk 0>;
> +			clock-input-name = "ipg";
> +			clock-output-name = "usboh3";
> +		};
> +
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