Re: [PATCH v14 1/1] clk: npcm8xx: add clock controller

[Stephen Boyd <sboyd@kernel.org>]

Quoting Tomer Maimon (2023-01-17 09:35:33)
> Hi Stephen,
> 
> Very sorry for the late reply.
> 
> On Fri, 16 Dec 2022 at 20:44, Stephen Boyd <sboyd@kernel.org> wrote:
> >
> > Quoting Tomer Maimon (2022-12-11 12:43:24)
> > > diff --git a/drivers/clk/clk-npcm8xx.c b/drivers/clk/clk-npcm8xx.c
> > > new file mode 100644
> > > index 000000000000..08ee7bea6f3a
> > > --- /dev/null
> > > +++ b/drivers/clk/clk-npcm8xx.c
> > > @@ -0,0 +1,650 @@
> > > +// SPDX-License-Identifier: GPL-2.0
> > > +/*
> > [...]
> > > +#define NPCM8XX_CLK_S_RCP        "rcp"
> > > +
> > > +static const u32 pll_mux_table[] = { 0, 1, 2, 3 };
> > > +static const struct clk_parent_data pll_mux_parents[] = {
> > > +       { .fw_name = NPCM8XX_CLK_S_PLL0, .name = NPCM8XX_CLK_S_PLL0 },
> >
> > As this is a new driver either you should only have .fw_name here. The
> > .name field is a backup to migrate code over to a new binding. When
> > .fw_name is used there should be an associated DT binding update. I
> What do you mean by associated DT binding? does the.fw_name, for
> example, NPCM8XX_CLK_S_PLL0 need to represent in the device tree?

Yes it should match a string in the "clock-names" property for this clk
provider's device node.

> > doubt the usage of .fw_name is correct though, because aren't these clks
> > internal to the controller? The .fw_name field is about describing does the
> yes the PLL clocks are internal.

Ok.

> > parents that are an input to the clk controller node in DT (because the
> > controller is a consumer of these clks that are external to the device).
> >
> > So can you use the .hw field for these internal clks? Check out
> > CLK_HW_INIT_HWS() macro and friends for a possible way to initialize
> > this.
> but still, I have used devm_clk_hw_register_mux_parent_data_table
> function to register the clock mux,
> should I use  devm_clk_hw_register_mux_parent_hws function instead?

Probably, yes.

> Does this modification need to be done in all the mux parent struct?
> could you point me to some example in the Linux kernel how do you
> think that I should represent the mux clock in the NPCM8XX clock
> driver?

I don't know. If the clk is external to the provider, then it should be
in .fw_name or .index and be provided through DT. Otherwise, if the clk
is internal to the clk provider use direct pointers.

> >
> > > +       { .fw_name = NPCM8XX_CLK_S_PLL1, .name = NPCM8XX_CLK_S_PLL1 },
> > > +       { .fw_name = NPCM8XX_CLK_S_REFCLK, .name = NPCM8XX_CLK_S_REFCLK },
> >
> > Maybe this is external? If so, it would be great to have this in the
> > binding as a `clocks` property.
> O.K.
> 

Is it external? If so, then fw_name would be correct. You can look at
the kernel-doc above clk_core_get(), but I really just need to spend a
few hours and write a proper kernel-doc for this stuff.