linux-kernel - Re: [PATCH v3 09/19] dt-bindings: nvmem: microchip-otpc: Add required clocks

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Message-ID: <f406abde-c7d1-4ed6-b7dd-5336956bc795@tuxon.dev>
Date: Sat, 31 Jan 2026 17:47:05 +0200
From: Claudiu Beznea <claudiu.beznea@...on.dev>
To: Alexander Dahl <ada@...rsis.com>
Cc: Nicolas Ferre <nicolas.ferre@...rochip.com>,
 Alexandre Belloni <alexandre.belloni@...tlin.com>,
 Ryan Wanner <ryan.wanner@...rochip.com>,
 linux-arm-kernel@...ts.infradead.org, devicetree@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-clk@...r.kernel.org,
 Srinivas Kandagatla <srini@...nel.org>, Rob Herring <robh@...nel.org>,
 Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>
Subject: Re: [PATCH v3 09/19] dt-bindings: nvmem: microchip-otpc: Add required
 clocks



On 1/20/26 17:44, Alexander Dahl wrote:
> The OTPC requires both the peripheral clock through PMC and the main RC
> oscillator.  Seemed to work without explicitly enabling those clocks on
> sama7g5 before, but did not on sam9x60.
> 
> Older datasheets were not clear and explicit about this, but recent are,
> e.g. SAMA7G5 series datasheet (DS60001765B),
> section 30.4.1 Power Management:
> 
>> The OTPC is clocked through the Power Management Controller (PMC).
>> The user must power on the main RC oscillator and enable the
>> peripheral clock of the OTPC prior to reading or writing the OTP
>> memory.

As this was not mentioned in the previous datasheet versions, the current driver 
don't handle those clocks, and it probably worked as the clocks were enabled by 
bootloaders, I think the clocks should be marked as required and this patch to 
be propagated as a fix along with fixes on driver and device trees.

I'll let DT binding maintainers for the final decision on this.

> 
> Link: https://lore.kernel.org/linux-clk/ec34efc2-2051-4b8a-b5d8-6e2fd5e08c28@microchip.com/T/#u

Why this link here?

> Signed-off-by: Alexander Dahl <ada@...rsis.com>
> ---
> 
> Notes:
>      v3:
>      - Removed clock-names (led to confusion, and not used by the driver anyways)
>      - Removed redundant example
>      
>      v2:
>      - new patch, not present in v1
> 
>   .../devicetree/bindings/nvmem/microchip,sama7g5-otpc.yaml | 8 ++++++++
>   1 file changed, 8 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/nvmem/microchip,sama7g5-otpc.yaml b/Documentation/devicetree/bindings/nvmem/microchip,sama7g5-otpc.yaml
> index 9a7aaf64eef32..847dfb67c6b72 100644
> --- a/Documentation/devicetree/bindings/nvmem/microchip,sama7g5-otpc.yaml
> +++ b/Documentation/devicetree/bindings/nvmem/microchip,sama7g5-otpc.yaml
> @@ -29,6 +29,11 @@ properties:
>     reg:
>       maxItems: 1
>   
> +  clocks:
> +    items:
> +      - description: main rc oscillator
> +      - description: otpc peripheral clock
> +
>   required:
>     - compatible
>     - reg
> @@ -37,6 +42,8 @@ unevaluatedProperties: false
>   
>   examples:
>     - |
> +    #include <dt-bindings/clock/at91.h>
> +    #include <dt-bindings/clock/microchip,sama7g5-pmc.h>
>       #include <dt-bindings/nvmem/microchip,sama7g5-otpc.h>
>   
>       otpc: efuse@...00000 {
> @@ -44,6 +51,7 @@ examples:
>           reg = <0xe8c00000 0xec>;
>           #address-cells = <1>;
>           #size-cells = <1>;
> +        clocks = <&pmc PMC_TYPE_CORE SAMA7G5_PMC_MAIN_RC>, <&pmc PMC_TYPE_PERIPHERAL 67>;
>   
>           temperature_calib: calib@1 {
>               reg = <OTP_PKT(1) 76>;