linux-kernel - Re: [PATCH v2 2/7] dt-bindings: clock: meson: a1: pll: introduce new syspll bindings

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Date: Sat, 11 May 2024 14:08:03 +0100
From: Conor Dooley <conor@...nel.org>
To: Dmitry Rokosov <ddrokosov@...utedevices.com>
Cc: neil.armstrong@...aro.org, jbrunet@...libre.com,
	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 v2 2/7] dt-bindings: clock: meson: a1: pll: introduce new
 syspll bindings

On Fri, May 10, 2024 at 12:08:54PM +0300, Dmitry Rokosov wrote:
> The 'syspll' PLL is a general-purpose PLL designed specifically for the
> CPU clock. It is capable of producing output frequencies within the
> range of 768MHz to 1536MHz.
> 
> The clock source sys_pll_div16, being one of the GEN clock parents,
> plays a crucial role and cannot be tagged as "optional". Unfortunately,
> it was not implemented earlier due to the cpu clock ctrl driver's
> pending status on the TODO list.

It's fine to not mark it optional in the binding, but it should be
optional in the driver as otherwise backwards compatibility will be
broken. Given this is an integral clock driver, sounds like it would
quite likely break booting on these devices if the driver doesn't treat
syspll_in as optional.
A lesson perhaps in describing the hardware entirely, even if the
drivers don't make use of all the information yet?

Cheers,
Conor.

> 
> Signed-off-by: Dmitry Rokosov <ddrokosov@...utedevices.com>
> ---
>  .../devicetree/bindings/clock/amlogic,a1-pll-clkc.yaml     | 7 +++++--
>  include/dt-bindings/clock/amlogic,a1-pll-clkc.h            | 2 ++
>  2 files changed, 7 insertions(+), 2 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/clock/amlogic,a1-pll-clkc.yaml b/Documentation/devicetree/bindings/clock/amlogic,a1-pll-clkc.yaml
> index a59b188a8bf5..fbba57031278 100644
> --- a/Documentation/devicetree/bindings/clock/amlogic,a1-pll-clkc.yaml
> +++ b/Documentation/devicetree/bindings/clock/amlogic,a1-pll-clkc.yaml
> @@ -26,11 +26,13 @@ properties:
>      items:
>        - description: input fixpll_in
>        - description: input hifipll_in
> +      - description: input syspll_in
>  
>    clock-names:
>      items:
>        - const: fixpll_in
>        - const: hifipll_in
> +      - const: syspll_in
>  
>  required:
>    - compatible
> @@ -53,7 +55,8 @@ examples:
>              reg = <0 0x7c80 0 0x18c>;
>              #clock-cells = <1>;
>              clocks = <&clkc_periphs CLKID_FIXPLL_IN>,
> -                     <&clkc_periphs CLKID_HIFIPLL_IN>;
> -            clock-names = "fixpll_in", "hifipll_in";
> +                     <&clkc_periphs CLKID_HIFIPLL_IN>,
> +                     <&clkc_periphs CLKID_SYSPLL_IN>;
> +            clock-names = "fixpll_in", "hifipll_in", "syspll_in";
>          };
>      };
> diff --git a/include/dt-bindings/clock/amlogic,a1-pll-clkc.h b/include/dt-bindings/clock/amlogic,a1-pll-clkc.h
> index 2b660c0f2c9f..a702d610589c 100644
> --- a/include/dt-bindings/clock/amlogic,a1-pll-clkc.h
> +++ b/include/dt-bindings/clock/amlogic,a1-pll-clkc.h
> @@ -21,5 +21,7 @@
>  #define CLKID_FCLK_DIV5		8
>  #define CLKID_FCLK_DIV7		9
>  #define CLKID_HIFI_PLL		10
> +#define CLKID_SYS_PLL		11
> +#define CLKID_SYS_PLL_DIV16	12
>  
>  #endif /* __A1_PLL_CLKC_H */
> -- 
> 2.43.0
> 
> 

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