by Krzysztof Kozlowski

[permalink] [raw]

Subject: Re: [PATCH v5 05/14] clk: Add generic driver for Maxim PMIC clocks

On śro, 2014-07-02 at 12:13 +0200, Javier Martinez Canillas wrote:
> Hello Mike,
>
> On 07/01/2014 07:26 PM, Mike Turquette wrote:
> > Quoting Yadwinder Singh Brar (2014-06-29 21:01:36)
> >> Hi Javier,
> >>
> >> On Thu, Jun 26, 2014 at 11:45 PM, Javier Martinez Canillas
> >> <[email protected]> wrote:
> >> > Maxim Integrated Power Management ICs are very similar with
> >> > regard to their clock outputs. Most of the clock drivers for
> >> > these chips are duplicating code and are simpler enough that
> >> > can be converted to use a generic driver to consolidate code
> >> > and avoid duplication.
> >> >
> >> > Signed-off-by: Javier Martinez Canillas <[email protected]>
> >> > Reviewed-by: Krzysztof Kozlowski <[email protected]>
> >> > ---
> >> >
> >> > Changes since v4:
> >> > - Return recalc 0 if clock isn't enabled in Suggested by Yadwinder Singh Brar.
> >> >
> >>
> >> It seems you didn't implement or posted same patch again :) .
> >>
> >> > Changes since v3:
> >> > - Add current copyright information. Suggested by Krzysztof Kozlowski
> >> > - Do a single allocation for struct max_gen_clk. Suggested by Krzysztof Kozlowski
> >> > - Add EXPORT_SYMBOL() for exported symbols. Suggested by Krzysztof Kozlowski
> >> >
> >> > drivers/clk/Kconfig | 3 +
> >> > drivers/clk/Makefile | 1 +
> >> > drivers/clk/clk-max-gen.c | 195 ++++++++++++++++++++++++++++++++++++++++++++++
> >> > drivers/clk/clk-max-gen.h | 32 ++++++++
> >> > 4 files changed, 231 insertions(+)
> >> > create mode 100644 drivers/clk/clk-max-gen.c
> >> > create mode 100644 drivers/clk/clk-max-gen.h
> >> >
> >>
> >> [ .. ]
> >>
> >> > +
> >> > +static unsigned long max_gen_recalc_rate(struct clk_hw *hw,
> >> > + unsigned long parent_rate)
> >> > +{
> >> > + return 32768;
> >> > +}
> >>
> >> Its still same here.
> >
> > Changing this would be a new behavior. I do not know of any other clock
> > drivers that conditionally returns a rate of 0 based on whether or not
> > the clock is gated.
> >
>
> After Yadwinder feedback I searched for clock drivers that returned 0 when the
> clock was not enabled/prepared and found for example drivers/clk/clk-s2mps11.c:
>
>
> static unsigned long s2mps11_clk_recalc_rate(struct clk_hw *hw,
> unsigned long parent_rate)
> {
> struct s2mps11_clk *s2mps11 = to_s2mps11_clk(hw);
> if (s2mps11->enabled)
> return 32768;
> else
> return 0;
> }
>
> > It is also buggy since calls to clk_enable and clk_disable do not invoke
> > .recalc_rate, so the rate of your clock would not be updated from the
> > framework's perspective until some later point where you call
> > clk_set_rate or something.
> >
>
> s2ps11->enabled is set in the driver's clk_ops .prepare and .unprepare function
> handlers and calls to clk_prepare and clk_unprepare also don't seems to invoke
> .recalc_rate so I guess that driver is wrong as well and should just return the
> clock rate unconditionally?

The s2mps11 may be not a best example for proper clock driver :).
Karol Wrona already sent a patch for s2mps11:
https://lkml.org/lkml/2014/7/1/389

Best regards,
Krzysztof

>
> > If your driver needs to know whether or not the clock is enabled then we
> > could introduce a new bool clk_is_enabled(struct clk *clk); to clk.h,
> > but I'd rather not do that. Instead if a driver needs a clock then it
> > calls clk_enable on it without any knowledge about the internal state of
> > the clock enable_count.
> >
> > Regards,
> > Mike
> >
>
> Thanks a lot for the explanation, I'll revert that change then and return the
> clock rate unconditionally on the next version of the patch-set.
>
> Best regards,
> Javier

2014-07-02 15:21:25

by Mike Turquette

[permalink] [raw]

Subject: Re: [PATCH v5 04/14] clk: max77686: Improve Maxim 77686 PMIC clocks binding

Quoting Javier Martinez Canillas (2014-07-02 03:17:54)
> Hello Mike,
>
> On 07/01/2014 07:29 PM, Mike Turquette wrote:
> > Quoting Javier Martinez Canillas (2014-06-26 11:15:36)
> >> Like most clock drivers, the Maxim 77686 PMIC clock binding
> >> follows the convention that the "#clock-cells" property is
> >> used to specify the number of cells in a clock provider.
> >>
> >> But the binding document is not clear enough that it shall
> >> be set to 1 since the PMIC support multiple clocks outputs.
> >>
> >> Also, explain that the clocks identifiers are defined in a
> >> header file that can be included by Device Tree source with
> >> client nodes to avoid using magic numbers.
> >>
> >> Signed-off-by: Javier Martinez Canillas <[email protected]>
> >> Reviewed-by: Krzysztof Kozlowski <[email protected]>
> >> Reviewed-by: Doug Anderson <[email protected]>
> >
> > Looks good to me.
> >
> > Regards,
> > Mike
> >
>
> Thanks a lot, an Acked-by or Reviewed-by tags for this patch and 03/14 will be
> great as well so I can carry those on the next version of the series.

Sure you can interpret my "looks good to me" as either an Ack or a
Reviewed-by, depending on context. In this case feel free to add:

Reviewed-by: Mike Turquette <[email protected]>

Regards,
Mike

>
> Best regards,
> Javier
>