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Date: Mon, 3 Jul 2017 15:58:34 +0200 From: Boris Brezillon <boris.brezillon@...e-electrons.com> To: Quentin Schulz <quentin.schulz@...e-electrons.com> Cc: mturquette@...libre.com, sboyd@...eaurora.org, robh+dt@...nel.org, mark.rutland@....com, nicolas.ferre@...rochip.com, alexandre.belloni@...e-electrons.com, linux@...linux.org.uk, lgirdwood@...il.com, broonie@...nel.org, perex@...ex.cz, tiwai@...e.com, linux-clk@...r.kernel.org, devicetree@...r.kernel.org, linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org, alsa-devel@...a-project.org, thomas.petazzoni@...e-electrons.com Subject: Re: [PATCH 1/6] clk: at91: clk-generated: remove useless divisor loop On Fri, 23 Jun 2017 11:00:54 +0200 Quentin Schulz <quentin.schulz@...e-electrons.com> wrote: > The driver requests the current clk rate of each of its parent clocks to > decide whether a clock rate is suitable or not. It does not request > determine_rate from a parent clock which could request a rate change in > parent clock (i.e. there is no parent rate propagation). > > We know the rate we want (passed along req argument of the function) and > the parent clock rate, thus we know the closest rounded divisor, we > don't need to iterate over the available divisors to find the best one > for a given clock. > > Signed-off-by: Quentin Schulz <quentin.schulz@...e-electrons.com> Acked-by: Boris Brezillon <boris.brezillon@...e-electrons.com> > --- > drivers/clk/at91/clk-generated.c | 25 ++++++++++++------------- > 1 file changed, 12 insertions(+), 13 deletions(-) > > diff --git a/drivers/clk/at91/clk-generated.c b/drivers/clk/at91/clk-generated.c > index 07c8f701e51c..dab7002937e6 100644 > --- a/drivers/clk/at91/clk-generated.c > +++ b/drivers/clk/at91/clk-generated.c > @@ -124,19 +124,18 @@ static int clk_generated_determine_rate(struct clk_hw *hw, > (gck->range.max && min_rate > gck->range.max)) > continue; > > - for (div = 1; div < GENERATED_MAX_DIV + 2; div++) { > - tmp_rate = DIV_ROUND_CLOSEST(parent_rate, div); > - tmp_diff = abs(req->rate - tmp_rate); > - > - if (best_diff < 0 || best_diff > tmp_diff) { > - best_rate = tmp_rate; > - best_diff = tmp_diff; > - req->best_parent_rate = parent_rate; > - req->best_parent_hw = parent; > - } > - > - if (!best_diff || tmp_rate < req->rate) > - break; > + div = DIV_ROUND_CLOSEST(parent_rate, req->rate); > + if (!div) > + tmp_rate = parent_rate; > + else > + tmp_rate = parent_rate / div; > + tmp_diff = abs(req->rate - tmp_rate); > + > + if (best_diff < 0 || best_diff > tmp_diff) { > + best_rate = tmp_rate; > + best_diff = tmp_diff; > + req->best_parent_rate = parent_rate; > + req->best_parent_hw = parent; > } > > if (!best_diff)
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