linux-kernel - Re: [PATCH v2 03/15] dt-bindings: devfreq: rk3399

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Date:   Fri, 4 Feb 2022 10:59:22 +0900
From:   Chanwoo Choi <cw00.choi@...sung.com>
To:     Brian Norris <briannorris@...omium.org>,
        MyungJoo Ham <myungjoo.ham@...sung.com>,
        Kyungmin Park <kyungmin.park@...sung.com>,
        Rob Herring <robh+dt@...nel.org>
Cc:     linux-kernel@...r.kernel.org, linux-rockchip@...ts.infradead.org,
        Lin Huang <hl@...k-chips.com>,
        linux-arm-kernel@...ts.infradead.org,
        Derek Basehore <dbasehore@...omium.org>,
        devicetree@...r.kernel.org, linux-pm@...r.kernel.org,
        Heiko Stuebner <heiko@...ech.de>
Subject: Re: [PATCH v2 03/15] dt-bindings: devfreq: rk3399_dmc: Fix Hz units

On 1/28/22 8:07 AM, Brian Norris wrote:
> The driver and all downstream device trees [1] are using Hz units, but
> the document claims MHz. DRAM frequency for these systems can't possibly
> exceed 2^32-1 Hz, so the choice of unit doesn't really matter than much.
> 
> Rather than add unnecessary risk in getting the units wrong, let's just
> go with the unofficial convention and make the docs match reality.
> 
> A sub-1MHz frequency is extremely unlikely, so include a minimum in the
> schema, to help catch anybody who might have believed this was MHz.
> 
> [1] And notably, also those trying to upstream them:
> https://protect2.fireeye.com/v1/url?k=0a7de78e-55e6dec8-0a7c6cc1-0cc47a3003e8-4f0969a9fa7b496e&q=1&e=6129c5df-8bd2-4072-86ef-79b79b36ec89&u=https%3A%2F%2Flore.kernel.org%2Flkml%2F20210308233858.24741-3-daniel.lezcano%40linaro.org%2F
> 
> Signed-off-by: Brian Norris <briannorris@...omium.org>
> ---
> 
> (no changes since v1)
> 
>  .../bindings/devfreq/rk3399_dmc.yaml          | 24 +++++++++----------
>  1 file changed, 12 insertions(+), 12 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/devfreq/rk3399_dmc.yaml b/Documentation/devicetree/bindings/devfreq/rk3399_dmc.yaml
> index fd62a8cd62d5..8bb778df92ae 100644
> --- a/Documentation/devicetree/bindings/devfreq/rk3399_dmc.yaml
> +++ b/Documentation/devicetree/bindings/devfreq/rk3399_dmc.yaml
> @@ -116,11 +116,11 @@ properties:
>  
>    rockchip,ddr3_odt_dis_freq:
>      $ref: /schemas/types.yaml#/definitions/uint32
> +    minimum: 1000000  # In case anyone thought this was MHz.
>      description:
>        When the DRAM type is DDR3, this parameter defines the ODT disable
> -      frequency in MHz (Mega Hz). When the DDR frequency is less then
> -      ddr3_odt_dis_freq, the ODT on the DRAM side and controller side are both
> -      disabled.
> +      frequency in Hz. When the DDR frequency is less then ddr3_odt_dis_freq,
> +      the ODT on the DRAM side and controller side are both disabled.
>  
>    rockchip,ddr3_drv:
>      deprecated: true
> @@ -160,11 +160,11 @@ properties:
>  
>    rockchip,lpddr3_odt_dis_freq:
>      $ref: /schemas/types.yaml#/definitions/uint32
> +    minimum: 1000000  # In case anyone thought this was MHz.
>      description:
>        When the DRAM type is LPDDR3, this parameter defines then ODT disable
> -      frequency in MHz (Mega Hz). When DDR frequency is less then
> -      ddr3_odt_dis_freq, the ODT on the DRAM side and controller side are both
> -      disabled.
> +      frequency in Hz. When DDR frequency is less then ddr3_odt_dis_freq, the
> +      ODT on the DRAM side and controller side are both disabled.
>  
>    rockchip,lpddr3_drv:
>      deprecated: true
> @@ -204,11 +204,11 @@ properties:
>  
>    rockchip,lpddr4_odt_dis_freq:
>      $ref: /schemas/types.yaml#/definitions/uint32
> +    minimum: 1000000  # In case anyone thought this was MHz.
>      description:
>        When the DRAM type is LPDDR4, this parameter defines the ODT disable
> -      frequency in MHz (Mega Hz). When the DDR frequency is less then
> -      ddr3_odt_dis_freq, the ODT on the DRAM side and controller side are both
> -      disabled.
> +      frequency in Hz. When the DDR frequency is less then ddr3_odt_dis_freq,
> +      the ODT on the DRAM side and controller side are both disabled.
>  
>    rockchip,lpddr4_drv:
>      deprecated: true
> @@ -287,7 +287,7 @@ examples:
>        rockchip,sr_mc_gate_idle = <0x3>;
>        rockchip,srpd_lite_idle = <0x4>;
>        rockchip,standby_idle = <0x2000>;
> -      rockchip,ddr3_odt_dis_freq = <333>;
> -      rockchip,lpddr3_odt_dis_freq = <333>;
> -      rockchip,lpddr4_odt_dis_freq = <333>;
> +      rockchip,ddr3_odt_dis_freq = <333000000>;
> +      rockchip,lpddr3_odt_dis_freq = <333000000>;
> +      rockchip,lpddr4_odt_dis_freq = <333000000>;
>      };
> 

Acked-by: Chanwoo Choi <cw00.choi@...sung.com>

-- 
Best Regards,
Chanwoo Choi
Samsung Electronics