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Message-ID: <20140524005640.23136.58952@quantum>
Date: Fri, 23 May 2014 17:56:40 -0700
From: Mike Turquette <mturquette@...aro.org>
To: Alex Elder <elder@...aro.org>, mporter@...aro.org,
bcm@...thebug.org
Cc: linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] clk: bcm/kona: implement determine_rate()
Quoting Alex Elder (2014-05-23 16:24:31)
> On 05/23/2014 06:18 PM, Mike Turquette wrote:
> > Quoting Alex Elder (2014-05-20 06:24:57)
> >> Implement the clk->determine_rate method for Broadcom Kona peripheral
> >> clocks. This allows a peripheral clock to be re-parented in order to
> >> satisfy a rate change request. This takes the place of the previous
> >> kona_peri_clk_round_rate() functionality, though that function remains
> >> because it is used by the new one.
> >>
> >> The parent clock that allows the peripheral clock to produce a rate
> >> closest to the one requested is the one selected, though the current
> >> parent is used by default.
> >>
> >> Signed-off-by: Alex Elder <elder@...aro.org>
> >> ---
> >> This patch is based on Mike Turquette's current "clk-next" branch.
> >> 6ed8eb5 Merge tag 'clk-hisi-for-v3.16' of https://git.kern...
> >>
> >> It is available here:
> >> http://git.linaro.org/landing-teams/working/broadcom/kernel.git
> >> Branch review/bcm-determine-rate
> >>
> >> drivers/clk/bcm/clk-kona.c | 53 +++++++++++++++++++++++++++++++++++++++++++++-
> >> 1 file changed, 52 insertions(+), 1 deletion(-)
> >>
> >> diff --git a/drivers/clk/bcm/clk-kona.c b/drivers/clk/bcm/clk-kona.c
> >> index d603c4e..1a4eccc 100644
> >> --- a/drivers/clk/bcm/clk-kona.c
> >> +++ b/drivers/clk/bcm/clk-kona.c
> >> @@ -1031,6 +1031,57 @@ static long kona_peri_clk_round_rate(struct clk_hw *hw, unsigned long rate,
> >> rate ? rate : 1, *parent_rate, NULL);
> >> }
> >>
> >> +static long kona_peri_clk_determine_rate(struct clk_hw *hw, unsigned long rate,
> >> + unsigned long *best_parent_rate, struct clk **best_parent)
> >> +{
> >> + struct kona_clk *bcm_clk = to_kona_clk(hw);
> >> + struct clk *clk = hw->clk;
> >> + struct clk *current_parent;
> >> + unsigned long parent_rate;
> >> + unsigned long best_delta;
> >> + unsigned long best_rate;
> >> + u32 parent_count;
> >> + u32 which;
> >> +
> >> + /*
> >> + * If there is no other parent to choose, use the current one.
> >> + * Note: We don't honor (or use) CLK_SET_RATE_NO_REPARENT.
> >> + */
> >
> > A WARN_ONCE is appropriate upon detection of CLK_SET_RATE_NO_REPARENT.
> > It will certainly help someone that is debugging why that flag has no
> > effect.
>
> I'll add that.
Thanks!
>
> > Otherwise the patch looks good to me.
>
> Would you like me to send an updated patch as a pull request?
It's up to you. For a single patch I can easily pick it. If you want to
bundle it up with the other pending patches (prereq clocks, etc) then a
pull request would be nice once all that stuff gets sorted.
Regards,
Mike
>
> Thanks.
>
> -Alex
>
> > Regards,
> > Mike
> >
> >> + parent_count = (u32)bcm_clk->init_data.num_parents;
> >> + if (parent_count < 2)
> >> + return kona_peri_clk_round_rate(hw, rate, best_parent_rate);
> >> +
> >> + /* Unless we can do better, stick with current parent */
> >> + current_parent = clk_get_parent(clk);
> >> + parent_rate = __clk_get_rate(current_parent);
> >> + best_rate = kona_peri_clk_round_rate(hw, rate, &parent_rate);
> >> + best_delta = abs(best_rate - rate);
> >> +
> >> + /* Check whether any other parent clock can produce a better result */
> >> + for (which = 0; which < parent_count; which++) {
> >> + struct clk *parent = clk_get_parent_by_index(clk, which);
> >> + unsigned long delta;
> >> + unsigned long other_rate;
> >> +
> >> + BUG_ON(!parent);
> >> + if (parent == current_parent)
> >> + continue;
> >> +
> >> + /* We don't support CLK_SET_RATE_PARENT */
> >> + parent_rate = __clk_get_rate(parent);
> >> + other_rate = kona_peri_clk_round_rate(hw, rate, &parent_rate);
> >> + delta = abs(other_rate - rate);
> >> + if (delta < best_delta) {
> >> + best_delta = delta;
> >> + best_rate = other_rate;
> >> + *best_parent = parent;
> >> + *best_parent_rate = parent_rate;
> >> + }
> >> + }
> >> +
> >> + return best_rate;
> >> +}
> >> +
> >> static int kona_peri_clk_set_parent(struct clk_hw *hw, u8 index)
> >> {
> >> struct kona_clk *bcm_clk = to_kona_clk(hw);
> >> @@ -1135,7 +1186,7 @@ struct clk_ops kona_peri_clk_ops = {
> >> .disable = kona_peri_clk_disable,
> >> .is_enabled = kona_peri_clk_is_enabled,
> >> .recalc_rate = kona_peri_clk_recalc_rate,
> >> - .round_rate = kona_peri_clk_round_rate,
> >> + .determine_rate = kona_peri_clk_determine_rate,
> >> .set_parent = kona_peri_clk_set_parent,
> >> .get_parent = kona_peri_clk_get_parent,
> >> .set_rate = kona_peri_clk_set_rate,
> >> --
> >> 1.9.1
> >>
>
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