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Message-ID: <01bac126-d057-d189-ca19-37db31057e99@linaro.org>
Date: Mon, 27 Mar 2023 15:55:46 +0200
From: neil.armstrong@...aro.org
To: Dmitry Rokosov <ddrokosov@...rdevices.ru>
Cc: mturquette@...libre.com, sboyd@...nel.org, robh+dt@...nel.org,
krzysztof.kozlowski+dt@...aro.org, khilman@...libre.com,
martin.blumenstingl@...glemail.com, jian.hu@...ogic.com,
kernel@...rdevices.ru, rockosov@...il.com,
linux-amlogic@...ts.infradead.org, linux-clk@...r.kernel.org,
devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v11 3/5] dt-bindings: clock: meson: add A1 PLL and
Peripherals clkcs bindings
On 27/03/2023 15:19, Dmitry Rokosov wrote:
> On Mon, Mar 27, 2023 at 02:03:25PM +0200, neil.armstrong@...aro.org wrote:
>> On 27/03/2023 13:39, Jerome Brunet wrote:
>>>
>>> On Mon 27 Mar 2023 at 13:51, Dmitry Rokosov <ddrokosov@...rdevices.ru> wrote:
>>>
>>>> On Mon, Mar 27, 2023 at 11:51:21AM +0200, Jerome Brunet wrote:
>>>>>
>>>>> On Tue 21 Mar 2023 at 22:30, Dmitry Rokosov <ddrokosov@...rdevices.ru> wrote:
>>>>>
>>>>>> Add the documentation for Amlogic A1 PLL and Amlogic A1 Peripherals
>>>>>> clock drivers.
>>>>>> Introduce Amlogic A1 PLL and Amlogic A1 Peripherals device tree
>>>>>> bindings and include them to MAINTAINERS.
>>>>>>
>>>>>> Signed-off-by: Jian Hu <jian.hu@...ogic.com>
>>>>>> Signed-off-by: Dmitry Rokosov <ddrokosov@...rdevices.ru>
>>>>>> ---
>>>>>> .../bindings/clock/amlogic,a1-clkc.yaml | 73 +++++++++++
>>>>>> .../bindings/clock/amlogic,a1-pll-clkc.yaml | 59 +++++++++
>>>>>> MAINTAINERS | 1 +
>>>>>> include/dt-bindings/clock/amlogic,a1-clkc.h | 113 ++++++++++++++++++
>>>>>> .../dt-bindings/clock/amlogic,a1-pll-clkc.h | 21 ++++
>>>>>> 5 files changed, 267 insertions(+)
>>>>>> create mode 100644 Documentation/devicetree/bindings/clock/amlogic,a1-clkc.yaml
>>>>>> create mode 100644 Documentation/devicetree/bindings/clock/amlogic,a1-pll-clkc.yaml
>>>>>
>>>>> There is two drivers (and 2 independent patches). There should be 2
>>>>> bindings patches as well.
>>>>>
>>>>
>>>> Before, in previous versions I had two versions, but it wasn't bisectable
>>>> approach.
>>>
>>> You are confusing bisectable and Rob's robot. Splitting patches is more
>>> that likely to help bisect (and patches backport) - not the other way around.
>>>
>>>> a1-clkc schema depends on a1-pll-clkc headers and vice versa.
>>>> It means dt schemas checkers will show us failure if we split them into two
>>>> patchsets.
>>>
>>> Only because you are patches are not upstream yet ...
>>>
>>>> I know, that we can use raw digits instead of CLKID names, but IMO it doesn't
>>>> look like production schema and it requires one more patchset above the
>>>> series with proper CLKID definitons usage and proper header including.
>>>>
>>>> BTW, there is an example of Rob's test bot failure found in the previous
>>>> v10 patch series due to chicken or the egg problem.
>>>> https://lore.kernel.org/all/167769997208.7087.5344356236212731922.robh@kernel.org/
>>>>
>>>> Please advise what's the best practice to resolve that..
>>>
>>> Don't use the header in your example would solve the problem and
>>> still be correct DT wise.
>>>
>>> The examples are just examples, they are not required to actually
>>> matches a real HW, as far as I know.
>>
>> Exact, you can use fake lables instead of defined:
>>
>> <&clkc_pll CLKID_FCLK_DIV2>,
>>
>> =>
>> remove "#include <dt-bindings/clock/amlogic,a1-pll-clkc.h>"
>>
>> <&clkc_pll_fclk_div2>,
>>
>> is perfectly ok and will permit have 2 separate patches.
>>
>> The dependency is only if you have a common yaml file for
>> both bindings files, but this is not the case here.
>
> Simple removal of "#include <dt-bindings/clock/amlogic,a1-pll-clkc.h>"
> header doesn't work, dt_binding_check make rule is failed:
I never wrote you to only remove the include, adding fake labels phandles was the logical next step.
Neil
>
> Error: Documentation/devicetree/bindings/clock/amlogic,a1-clkc.example.dts:28.37-38 syntax error
> FATAL ERROR: Unable to parse input tree
>
> It happens, because 'dt_binding_check' generates simple dts example and
> tries to compile it:
>
> cat Documentation/devicetree/bindings/clock/amlogic,a1-clkc.example.dts
> ===
>
> /dts-v1/;
> /plugin/; // silence any missing phandle references
>
>
> /{
> compatible = "foo";
> model = "foo";
> #address-cells = <1>;
> #size-cells = <1>;
>
>
>
> example-0 {
> #address-cells = <1>;
> #size-cells = <1>;
>
>
>
> apb {
> #address-cells = <2>;
> #size-cells = <2>;
>
> clock-controller@800 {
> compatible = "amlogic,a1-clkc";
> reg = <0 0x800 0 0x104>;
> #clock-cells = <1>;
> clocks = <&clkc_pll CLKID_FCLK_DIV2>,
> <&clkc_pll CLKID_FCLK_DIV3>,
> <&clkc_pll CLKID_FCLK_DIV5>,
> <&clkc_pll CLKID_FCLK_DIV7>,
> <&clkc_pll CLKID_HIFI_PLL>,
> <&xtal>;
> clock-names = "fclk_div2", "fclk_div3",
> "fclk_div5", "fclk_div7",
> "hifi_pll", "xtal";
> };
> };
>
> };
> };
> ===
>
> As you can see, header is required.
>
> But looks like, dt binding checker is happy with the fake references hack :)
> Below there is generated example dts:
>
> cat Documentation/devicetree/bindings/clock/amlogic,a1-clkc.example.dts
> ===
>
> /dts-v1/;
> /plugin/; // silence any missing phandle references
>
>
> /{
> compatible = "foo";
> model = "foo";
> #address-cells = <1>;
> #size-cells = <1>;
>
>
>
> example-0 {
> #address-cells = <1>;
> #size-cells = <1>;
>
>
>
> apb {
> #address-cells = <2>;
> #size-cells = <2>;
>
> clock-controller@800 {
> compatible = "amlogic,a1-clkc";
> reg = <0 0x800 0 0x104>;
> #clock-cells = <1>;
> clocks = <&clkc_pll_fclk_div2>,
> <&clkc_pll_fclk_div3>,
> <&clkc_pll_fclk_div5>,
> <&clkc_pll_fclk_div7>,
> <&clkc_pll_hifi_pll>,
> <&xtal>;
> clock-names = "fclk_div2", "fclk_div3",
> "fclk_div5", "fclk_div7",
> "hifi_pll", "xtal";
> };
> };
>
> };
> };
> ===
>
> Yep, we are able to cheat dt checkers, but we don't help dt developers
> with such example.
> May be, it's better to prepare two patches in such hierarchy:
>
> 1) A1 PLL clkc bindings with fake references without clkc headers
> 2) A1 clkc bindings with real CLKID bindings + A1 PLL clkc bindings fix
> with real CLKID A1 clkc bindings + header.
>
> The such approach resolves DT checkers failures and split DT bindings
> into two patchsets.
>
> [...]
>
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