Re: [PATCH v2 08/16] dt-bindings: nvmem: microchip-otpc: Add required clocks

Alexander Dahl
2025-02-11T07:05:22Z

Hello Krzysztof,

Am Mon, Feb 10, 2025 at 05:59:52PM +0100 schrieb Krzysztof Kozlowski:
> On 10/02/2025 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.
> >
> > Link: https://lore.kernel.org/linux-clk/ec34efc2-2051-4b8a-b5d8-6e2fd5e08c28@microchip.com/T/#u
> > Signed-off-by: Alexander Dahl <ada@thorsis.com>
> > ---
> >
> > Notes:
> > v2:
> > - new patch, not present in v1
> >
> > .../nvmem/microchip,sama7g5-otpc.yaml | 28 +++++++++++++++++++
> > 1 file changed, 28 insertions(+)
> >
> > diff --git a/Documentation/devicetree/bindings/nvmem/microchip,sama7g5-otpc.yaml b/Documentation/devicetree/bindings/nvmem/microchip,sama7g5-otpc.yaml
> > index 9a7aaf64eef32..1fa40610888f3 100644
> > --- a/Documentation/devicetree/bindings/nvmem/microchip,sama7g5-otpc.yaml
> > +++ b/Documentation/devicetree/bindings/nvmem/microchip,sama7g5-otpc.yaml
> > @@ -29,6 +29,16 @@ properties:
> > reg:
> > maxItems: 1
> >
> > + clocks:
> > + items:
> > + - description: main rc oscillator
> > + - description: otpc peripheral clock
> > +
> > + clock-names:
> > + items:
> > + - const: main_rc_osc
>
> osc

On at91 SoCs main oscillator and main RC oscillator are two different
things, and those are different clocks in Linux as well. This clock
is named "main_rc_osc" in the clock driver. In
drivers/clk/at91/sam9x60.c this clock is added like this:

hw = at91_clk_register_main_rc_osc(regmap, "main_rc_osc", 12000000, 50000000);

The datasheet makes it explicit, it's exactly the main rc oscillator
clock required for the OTPC to work, no other clock.

So why name this "osc" only then? This is confusing at best.

>
> > + - const: otpc_clk
>
> otpc or bus or whatever logically this is

Okay the "_clk" suffix is redundant. Since the peripheral clock for
the OTPC is required here, I would go with "otpc" only then.

>
> > +
> > required:
> > - compatible
> > - reg
> > @@ -37,6 +47,8 @@ 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@e8c00000 {
> > @@ -44,10 +56,26 @@ examples:
> > reg = <0xe8c00000 0xec>;
> > #address-cells = <1>;
> > #size-cells = <1>;
> > + clocks = <&pmc PMC_TYPE_CORE SAMA7G5_PMC_MAIN_RC>, <&pmc PMC_TYPE_PERIPHERAL 67>;
> > + clock-names = "main_rc_osc", "otpc_clk";
> >
> > temperature_calib: calib@1 {
> > reg = <OTP_PKT(1) 76>;
> > };
> > };
> >
> > + - |
> > + #include <dt-bindings/clock/at91.h>
> > + #include <dt-bindings/clock/microchip,sam9x60-pmc.h>
> > + #include <dt-bindings/nvmem/microchip,sama7g5-otpc.h>
> > +
> > + efuse@eff00000 {
> > + compatible = "microchip,sam9x60-otpc", "syscon";
> > + reg = <0xeff00000 0xec>;
>
> No need for new example with difference in what exactly? Even compatible
> was not added here...

Different compatible, different clocks, no sub nodes, different
peripheral clock id … From a human doc readers I'd like another
example, but fine, we can drop it if it adds too much redundancy.

Greets
Alex

>
> > + #address-cells = <1>;
> > + #size-cells = <1>;
> > + clocks = <&pmc PMC_TYPE_CORE SAM9X60_PMC_MAIN_RC>, <&pmc PMC_TYPE_PERIPHERAL 46>;
> > + clock-names = "main_rc_osc", "otpc_clk";
> > + };
> > +
> > ...
>
>
> Best regards,
> Krzysztof