Re: [PATCH v4 3/8] clk: add support for clocks provided by SCP(System Control Processor)

[Sudeep Holla]

Hi Stephen,


Thanks for the review.

On 02/07/15 18:23, Stephen Boyd wrote:
> On 06/08, Sudeep Holla wrote:
> > diff --git a/drivers/clk/Kconfig b/drivers/clk/Kconfig
> > index 9897f353bf1a..0fe8daefc105 100644
> > --- a/drivers/clk/Kconfig
> > +++ b/drivers/clk/Kconfig
> > @@ -59,6 +59,16 @@ config COMMON_CLK_RK808
> >   	  clocked at 32KHz each. Clkout1 is always on, Clkout2 can off
> >   	  by control register.
> >
> > +config COMMON_CLK_SCPI
> > +        tristate "Clock driver controlled via SCPI interface"
> > +        depends on ARM_SCPI_PROTOCOL || COMPILE_TEST
> > +        ---help---
> > +          This driver provides support for clocks that are controlled
> > +          by firmware that implements the SCPI interface.
> > +
> > +	  This driver uses SCPI Message Protocol to interact with the
> > +	  firmware providing all the clock controls.
>
> The tabbing is weird here. Both paragraphs should have the same
> alignment.

Indeed, sorry for that, fixed now.

> > diff --git a/drivers/clk/clk-scpi.c b/drivers/clk/clk-scpi.c
> > new file mode 100644
> > index 000000000000..707b3430c55f
> > --- /dev/null
> > +++ b/drivers/clk/clk-scpi.c
> > +
> > +#include <linux/clk-provider.h>
> > +#include <linux/device.h>
> > +#include <linux/err.h>
> > +#include <linux/of.h>
> > +#include <linux/module.h>
> > +#include <linux/of_platform.h>
> > +#include <linux/scpi_protocol.h>
>
> Please include <linux/platform_device.h> as well.

Added now, didn't bother as of_platform.h includes it.

> > +
> > +struct scpi_clk {
> > +	u32 id;
> > +	const char *name;
>
> Do you need this? Or can you just use __clk_get_name() in places
> where the name is used?

Not used, so removed it.


[...]

> > +static long scpi_clk_round_rate(struct clk_hw *hw, unsigned long rate,
> > +				unsigned long *parent_rate)
> > +{
>
> Maybe a comment here like:
>
> /*
>   * We can't figure out what rate it will be, so just return the rate
>   * back to the caller. scpi_clk_recalc_rate() will be called
>   * after the rate is set and we'll know what rate the clock is
>   * running at then.
>   */

Done

> > +	return rate;
> > +}
> > +
> > +static int scpi_clk_set_rate(struct clk_hw *hw, unsigned long rate,
> > +			     unsigned long parent_rate)
> > +{
> > +	struct scpi_clk *clk = to_scpi_clk(hw);
> > +
> > +	return clk->scpi_ops->clk_set_val(clk->id, rate);
> > +}
> > +
> > +static void scpi_clk_disable(struct clk_hw *hw)
> > +{
> > +	scpi_clk_set_rate(hw, 0, 0);
>
> Does this mean you have to set a rate to enable the clock? Are
> you relying on drivers to call clk_set_rate() to implicitly
> enable the clock? If so, it would be better to cache the rate of
> the clock in set_rate if the clock isn't enabled in software and
> then send the cached rate during enable.

Agreed, I have asked the firmware/SCPI specification guys about
more details on what to expect from firmware. Once they get back,
will update the code considering your feedback.

[...]

> > +static int __scpi_find_dvfs_index(struct scpi_clk *clk, unsigned long rate)
> > +{
> > +	int idx, max_opp = clk->info->count;
> > +	struct scpi_opp *opp = clk->info->opps;
>
> const?

All the 3 above fixed now.

[...]

> > +
> > +	clk = devm_clk_register(dev, &sclk->hw);
> > +	if (!IS_ERR(clk) && max)
> > +		clk_set_rate_range(clk, min, max);
>
> Hm.. we're planning to make clk_register() return a struct
> clk_hw, so this will block that. We need some sort of clk_hw API
> that allows us to setup min/max limits on the clock from the
> provider side. Care to add that?

Can you provide pointer to the patches or the tree containing those
changes ? Are they targeted for v4.3 ?

Regards,
Sudeep
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