From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933637AbdGCN6l (ORCPT ); Mon, 3 Jul 2017 09:58:41 -0400 Received: from mail.free-electrons.com ([62.4.15.54]:47012 "EHLO mail.free-electrons.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755773AbdGCN6g (ORCPT ); Mon, 3 Jul 2017 09:58:36 -0400 Date: Mon, 3 Jul 2017 15:58:34 +0200 From: Boris Brezillon To: Quentin Schulz Cc: mturquette@baylibre.com, sboyd@codeaurora.org, robh+dt@kernel.org, mark.rutland@arm.com, nicolas.ferre@microchip.com, alexandre.belloni@free-electrons.com, linux@armlinux.org.uk, lgirdwood@gmail.com, broonie@kernel.org, perex@perex.cz, tiwai@suse.com, linux-clk@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, alsa-devel@alsa-project.org, thomas.petazzoni@free-electrons.com Subject: Re: [PATCH 1/6] clk: at91: clk-generated: remove useless divisor loop Message-ID: <20170703155834.4de2a304@bbrezillon> In-Reply-To: <20170623090059.8371-2-quentin.schulz@free-electrons.com> References: <20170623090059.8371-1-quentin.schulz@free-electrons.com> <20170623090059.8371-2-quentin.schulz@free-electrons.com> X-Mailer: Claws Mail 3.13.2 (GTK+ 2.24.30; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 23 Jun 2017 11:00:54 +0200 Quentin Schulz 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 Acked-by: Boris Brezillon > --- > 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)