Re: [PATCH v1 09/12] clk: at91: sam9x60: Allow enabling main_rc_osc through DT

Alexander Dahl
2024-09-19T12:39:52Z

Hello Claudiu,

after being busy with other things, I'm back looking at this series.
As Nicolas pointed out [1], we need three clocks for the OTPC to work,
quote:

"for all the products, the main RC oscillator, the OTPC peripheral
clock and the MCKx clocks associated to OTP must be enabled."

I have a problem with making the main_rc_osc accessible for both
SAM9X60 and SAMA7G5 here, see below.

Am Wed, Aug 21, 2024 at 12:59:40PM +0200 schrieb Alexander Dahl:
> SAM9X60 Datasheet (DS60001579G) Section "23.4 Product Dependencies"
> says:
>
> "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."
>
> The code for enabling/disabling that clock is already present, it was
> just not possible to hook into DT anymore, after at91 clk devicetree
> binding rework back in 2018 for kernel v4.19.
>
> Signed-off-by: Alexander Dahl <ada@thorsis.com>
> ---
> drivers/clk/at91/sam9x60.c | 3 ++-
> include/dt-bindings/clock/at91.h | 1 +
> 2 files changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/clk/at91/sam9x60.c b/drivers/clk/at91/sam9x60.c
> index e309cbf3cb9a..4d5ee20b8fc4 100644
> --- a/drivers/clk/at91/sam9x60.c
> +++ b/drivers/clk/at91/sam9x60.c
> @@ -207,7 +207,7 @@ static void __init sam9x60_pmc_setup(struct device_node *np)
> if (IS_ERR(regmap))
> return;
>
> - sam9x60_pmc = pmc_data_allocate(PMC_PLLACK + 1,
> + sam9x60_pmc = pmc_data_allocate(PMC_MAIN_RC + 1,
> nck(sam9x60_systemck),
> nck(sam9x60_periphck),
> nck(sam9x60_gck), 8);
> @@ -218,6 +218,7 @@ static void __init sam9x60_pmc_setup(struct device_node *np)
> 50000000);
> if (IS_ERR(hw))
> goto err_free;
> + sam9x60_pmc->chws[PMC_MAIN_RC] = hw;
>
> hw = at91_clk_register_main_osc(regmap, "main_osc", mainxtal_name, NULL, 0);
> if (IS_ERR(hw))
> diff --git a/include/dt-bindings/clock/at91.h b/include/dt-bindings/clock/at91.h
> index 3e3972a814c1..f957625cb3ac 100644
> --- a/include/dt-bindings/clock/at91.h
> +++ b/include/dt-bindings/clock/at91.h
> @@ -25,6 +25,7 @@
> #define PMC_PLLBCK 8
> #define PMC_AUDIOPLLCK 9
> #define PMC_AUDIOPINCK 10
> +#define PMC_MAIN_RC 11
>
> /* SAMA7G5 */
> #define PMC_CPUPLL (PMC_MAIN + 1)

There are IDs defined in the devicetree bindings here, which are used
both in dts and in driver code as array indexes. In v1 of the patch
series I just added a new last element in the end of the generic list
and used that for SAM9X60.

For SAMA7G5 those IDs are branched of from PMC_MAIN in between, making
SAMA7G5 using a different last element, and different values after
PMC_MAIN.

Now we need a new ID for main rc osc, but not only for SAM9X60, but
also for SAMA7G5. I'm not sure what the implications would be, if the
new ID would be added in between before PMC_MAIN, so all values would
change? Adding it to the end of the lists would probably be safe, but
then you would need a diffently named variant for SAMA7G5's different
IDs. I find the current status somewhat unfortunate for future
extensions. How should this new ID be added here? What would be the
way forward?

Greets
Alex

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

> --
> 2.39.2
>
>