[PATCH 2/3] clk: ux500: Support prcmu ape opp voltage clock

[mturquette@ti.com (Mike Turquette)]

Quoting Ulf Hansson (2012-09-25 00:56:56)
> Hi Mike,
> 
> Thanks for your input!
> 
> On 24 September 2012 17:35, Mike Turquette <mturquette@ti.com> wrote:
> > Quoting Ulf Hansson (2012-09-24 07:43:18)
> >> From: Ulf Hansson <ulf.hansson@linaro.org>
> >>
> >> Some scalable prcmu clocks needs to be handled in conjuction with the
> >> ape opp 100 voltage. A new prcmu clock type clk_prcmu_opp_volt_scalable
> >> is implemented to handle this.
> >>
> >> Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
> >> ---
> >>  drivers/clk/ux500/clk-prcmu.c |   55 +++++++++++++++++++++++++++++++++++++++++
> >>  drivers/clk/ux500/clk.h       |    6 +++++
> >>  2 files changed, 61 insertions(+)
> >>
> >> diff --git a/drivers/clk/ux500/clk-prcmu.c b/drivers/clk/ux500/clk-prcmu.c
> >> index 930cdfe..04577ca 100644
> >> --- a/drivers/clk/ux500/clk-prcmu.c
> >> +++ b/drivers/clk/ux500/clk-prcmu.c
> >> @@ -133,6 +133,40 @@ out_error:
> >>                 hw->init->name);
> >>  }
> >>
> >> +static int clk_prcmu_opp_volt_prepare(struct clk_hw *hw)
> >> +{
> >> +       int err;
> >> +       struct clk_prcmu *clk = to_clk_prcmu(hw);
> >> +
> >> +       err = prcmu_request_ape_opp_100_voltage(true);
> >> +       if (err) {
> >> +               pr_err("clk_prcmu: %s failed to request APE OPP VOLT for %s.\n",
> >> +                       __func__, hw->init->name);
> >> +               return err;
> >> +       }
> >> +
> >> +       err = prcmu_request_clock(clk->cg_sel, true);
> >> +       if (err)
> >> +               prcmu_request_ape_opp_100_voltage(false);
> >> +
> >> +       return err;
> >> +}
> >> +
> >> +static void clk_prcmu_opp_volt_unprepare(struct clk_hw *hw)
> >> +{
> >> +       struct clk_prcmu *clk = to_clk_prcmu(hw);
> >> +
> >> +       if (prcmu_request_clock(clk->cg_sel, false))
> >> +               goto out_error;
> >> +       if (prcmu_request_ape_opp_100_voltage(false))
> >> +               goto out_error;
> >> +       return;
> >> +
> >> +out_error:
> >> +       pr_err("clk_prcmu: %s failed to disable %s.\n", __func__,
> >> +               hw->init->name);
> >> +}
> >
> > Hello Ulf,
> >
> > I was hoping to use the rate-change notifiers for voltage scaling, as in
> > my clk reentrancy/dvfs RFCs.  Using prepare/unprepare to set voltage for
> > non-scalable clocks is probably OK; do you plan to scale voltage when
> > your clocks change rate?  If so then you will need more than just
> > prepare/unprepare.
> 
> I see, you have a good point here. Although right now this clock will
> never change rate except during "init". Prepare/unprepare is thus
> enough.
> 
> For the u8500 platform the sdmmc clock is the parent for all the
> mmc/sd/sdio controllers. So, to no introduce a very complex
> clockhandling mechanism (using rate-change notifiers would help a bit,
> but is not enough), the clock is not supposed to be changed after
> init. Proper dividing of the clock is handled internally by each
> controller instead.
> 

The internal dividers could be modeled as clk nodes, which themselves
could have notifier handlers that scale voltage.  So perhaps the MMC
controller driver for your platform should define the appropriate leaf
clks?

Regards,
Mike

> 
> >
> > Regards,
> > Mike
> >
> >> +
> >>  static struct clk_ops clk_prcmu_scalable_ops = {
> >>         .prepare = clk_prcmu_prepare,
> >>         .unprepare = clk_prcmu_unprepare,
> >> @@ -167,6 +201,17 @@ static struct clk_ops clk_prcmu_opp_gate_ops = {
> >>         .recalc_rate = clk_prcmu_recalc_rate,
> >>  };
> >>
> >> +static struct clk_ops clk_prcmu_opp_volt_scalable_ops = {
> >> +       .prepare = clk_prcmu_opp_volt_prepare,
> >> +       .unprepare = clk_prcmu_opp_volt_unprepare,
> >> +       .enable = clk_prcmu_enable,
> >> +       .disable = clk_prcmu_disable,
> >> +       .is_enabled = clk_prcmu_is_enabled,
> >> +       .recalc_rate = clk_prcmu_recalc_rate,
> >> +       .round_rate = clk_prcmu_round_rate,
> >> +       .set_rate = clk_prcmu_set_rate,
> >> +};
> >> +
> >>  static struct clk *clk_reg_prcmu(const char *name,
> >>                                  const char *parent_name,
> >>                                  u8 cg_sel,
> >> @@ -250,3 +295,13 @@ struct clk *clk_reg_prcmu_opp_gate(const char *name,
> >>         return clk_reg_prcmu(name, parent_name, cg_sel, 0, flags,
> >>                         &clk_prcmu_opp_gate_ops);
> >>  }
> >> +
> >> +struct clk *clk_reg_prcmu_opp_volt_scalable(const char *name,
> >> +                                           const char *parent_name,
> >> +                                           u8 cg_sel,
> >> +                                           unsigned long rate,
> >> +                                           unsigned long flags)
> >> +{
> >> +       return clk_reg_prcmu(name, parent_name, cg_sel, rate, flags,
> >> +                       &clk_prcmu_opp_volt_scalable_ops);
> >> +}
> >> diff --git a/drivers/clk/ux500/clk.h b/drivers/clk/ux500/clk.h
> >> index 836d7d1..f36eeed 100644
> >> --- a/drivers/clk/ux500/clk.h
> >> +++ b/drivers/clk/ux500/clk.h
> >> @@ -45,4 +45,10 @@ struct clk *clk_reg_prcmu_opp_gate(const char *name,
> >>                                    u8 cg_sel,
> >>                                    unsigned long flags);
> >>
> >> +struct clk *clk_reg_prcmu_opp_volt_scalable(const char *name,
> >> +                                           const char *parent_name,
> >> +                                           u8 cg_sel,
> >> +                                           unsigned long rate,
> >> +                                           unsigned long flags);
> >> +
> >>  #endif /* __UX500_CLK_H */
> >> --
> >> 1.7.10
> 
> Kind regards
> Ulf Hansson