[RFC v2: PATCH 1/2] dt-bindings: Document the hi3660 reset bindings

[Philipp Zabel]

Am Freitag, den 25.11.2016, 20:08 +0800 schrieb zhangfei:
> 
> On 2016年11月25日 18:54, Philipp Zabel wrote:
> > Am Freitag, den 25.11.2016, 18:42 +0800 schrieb zhangfei:
> >> On 2016年11月25日 18:25, Philipp Zabel wrote:
> >>> Am Donnerstag, den 24.11.2016, 18:20 +0800 schrieb zhangfei:
> >>>> On 2016年11月24日 17:50, Philipp Zabel wrote:
> >>>>> Am Donnerstag, den 24.11.2016, 17:40 +0800 schrieb zhangfei:
> >>>>>> On 2016年11月24日 17:26, Philipp Zabel wrote:
> >>>>>>> Am Mittwoch, den 23.11.2016, 16:07 +0800 schrieb Zhangfei Gao:
> >>>>>>>> Add DT bindings documentation for hi3660 SoC reset controller.
> >>>>>>>>
> >>>>>>>> Signed-off-by: Zhangfei Gao <zhangfei.gao at linaro.org>
> >>>>>>>> ---
> >>>>>>>>      .../bindings/reset/hisilicon,hi3660-reset.txt      | 51 ++++++++++++++++++++++
> >>>>>>>>      1 file changed, 51 insertions(+)
> >>>>>>>>      create mode 100644 Documentation/devicetree/bindings/reset/hisilicon,hi3660-reset.txt
> >>>>>>>>
> >>>>>>>> diff --git a/Documentation/devicetree/bindings/reset/hisilicon,hi3660-reset.txt b/Documentation/devicetree/bindings/reset/hisilicon,hi3660-reset.txt
> >>>>>>>> new file mode 100644
> >>>>>>>> index 0000000..250daf2
> >>>>>>>> --- /dev/null
> >>>>>>>> +++ b/Documentation/devicetree/bindings/reset/hisilicon,hi3660-reset.txt
> >>>>>>>> @@ -0,0 +1,51 @@
> >>>>>>>> +Hisilicon System Reset Controller
> >>>>>>>> +======================================
> >>>>>>>> +
> >>>>>>>> +Please also refer to reset.txt in this directory for common reset
> >>>>>>>> +controller binding usage.
> >>>>>>>> +
> >>>>>>>> +The reset controller registers are part of the system-ctl block on
> >>>>>>>> +hi3660 SoC.
> >>>>>>>> +
> >>>>>>>> +Required properties:
> >>>>>>>> +- compatible: should be
> >>>>>>>> +		 "hisilicon,hi3660-reset"
> >>>>>>>> +- #reset-cells: 1, see below
> >>>>>>>> +- hisi,rst-syscon: phandle of the reset's syscon.
> >>>>>>>> +- hisi,reset-bits: Contains the reset control register information
> >>>>>>>> +		  Should contain 2 cells for each reset exposed to
> >>>>>>>> +		  consumers, defined as:
> >>>>>>>> +			Cell #1 : offset from the syscon register base
> >>>>>>>> +			Cell #2 : bits position of the control register
> >>>>>>>> +
> >>>>>>>> +Example:
> >>>>>>>> +	iomcu: iomcu at ffd7e000 {
> >>>>>>>> +		compatible = "hisilicon,hi3660-iomcu", "syscon";
> >>>>>>>> +		reg = <0x0 0xffd7e000 0x0 0x1000>;
> >>>>>>>> +	};
> >>>>>>>> +
> >>>>>>>> +	iomcu_rst: iomcu_rst_controller {
> >>>>>>> This should be
> >>>>>>> 	iomcu_rst: reset-controller {
> >>>>>>>
> >>>>>>>> +		compatible = "hisilicon,hi3660-reset";
> >>>>>>>> +		#reset-cells = <1>;
> >>>>>>>> +		hisi,rst-syscon = <&iomcu>;
> >>>>>>>> +		hisi,reset-bits = <0x20 0x8		/* 0: i2c0 */
> >>>>>>>> +				   0x20 0x10		/* 1: i2c1 */
> >>>>>>>> +				   0x20 0x20		/* 2: i2c2 */
> >>>>>>>> +				   0x20 0x8000000>;	/* 3: i2c6 */
> >>>>>>>> +	};
> >>>>>>> The reset lines are controlled through iomcu bits, is there a reason not
> >>>>>>> to put the iomcu_rst node inside the iomcu node? That way the
> >>>>>>> hisi,rst-syscon property could be removed and the syscon could be
> >>>>>>> retrieved via the reset-controller parent node.
> >>>>>> iomcu is common registers, controls clock and reset, etc.
> >>>>>> So we use syscon, without mapping the registers everywhere.
> >>>>>> It is common case in hisilicon, same in hi6220.
> >>>>>>
> >>>>>> Also the #clock-cells and #reset-cells can not be put in the same node,
> >>>>>> if they are both using probe, since reset_probe will not be called.
> >>>>>>
> >>>>>> So we use hisi,rst-syscon as a general solution.
> >>>>> What I meant is this:
> >>>>>
> >>>>> 	iomcu: iomcu at ffd7e000 {
> >>>>> 		compatible = "hisilicon,hi3660-iomcu", "syscon", "simple-mfd";
> >>>>> 		reg = <0x0 0xffd7e000 0x0 0x1000>;
> >>>> #clock-cells = <1>;
> >>>>
> >>>> In my test, if there add #clock-cells = <1>, reset_probe will not be
> >>>> called any more.
> >>>> Since clk_probe is called first.
> >>>> No matter iomcu_rst is child node or not.
> >>> I don't understand this, does the clock driver bind to the iomcu node
> >>> using CLK_OF_DECLARE_DRIVER(..., "hisilicon,hi3660-iomcu", ...)?
> >> This method:CLK_OF_DECLARE_DRIVER is not prefered in clock,
> >> and we have to use probe instead, to make all driver build as modules as
> >> possible.
> >>
> >> For example hi3660.
> >> static struct platform_driver hi3660_clk_driver = {
> >>           .probe          = hi3660_clk_probe,
> >>           .driver         = {
> >>                   .name   = "hi3660-clk",
> >>                   .of_match_table = hi3660_clk_match_table,
> >>           },
> >> };
> > hi3660_clk_match_table contains the "hisilicon,hi3660-iomcu" compatible?
> > If so, you could call
> > 	of_platform_populate(pdev->dev.of_node, NULL, NULL, &pdev->dev);
> > from hi3660_clk_probe instead of using "simple-mfd" to probe the iomcu
> > node's children.
> 
> Not using simple-mfd:
> 
> Like
> static const struct of_device_id hi3660_clk_match_table[] = {
>          { .compatible = "hisilicon,hi3660-iomcu", },
>          { }
> };
> MODULE_DEVICE_TABLE(of, hi3660_clk_match_table);
> 
> static int hi3660_clk_probe(struct platform_device *pdev)
> {
>          struct device *dev = &pdev->dev;
>          struct device_node *np = pdev->dev.of_node;
>          const struct of_device_id *of_id;
>          enum hi3660_clk_type type;
> 
>          of_id = of_match_device(hi3660_clk_match_table, dev);
>          if (!of_id)
>                  return -EINVAL;
> ~
> }
> 
> If put iomcu_rst as child node, and set #clock-cells = <1> to iomcu,
> then hi3660_clk_probe is called, hi3660_reset_probe will not be called.

For hi3660_reset_probe to be called, you'll have to call
of_platform_populate to probe the hi3660-iomcu children in this case.

> So using "hisi,rst-syscon" as pointer does not have the issue.

I understand that, it still sounds to me like you are organizing the
device tree around limitations of the current code. Instead the device
tree should be organized to best describe the hardware, and the code
should be adapted to support that.

Of course, if you use the flat DT layout everywhere else, I won't try to
block the reset driver because of this issue. I'm just saying nested
nodes in the DT would better describe the real control flow.

regards
Philipp