Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933018AbeAIPyq convert rfc822-to-8bit (ORCPT + 1 other); Tue, 9 Jan 2018 10:54:46 -0500 Received: from mailoutvs3.siol.net ([213.250.19.136]:39373 "EHLO mail.siol.net" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1758665AbeAIPym (ORCPT ); Tue, 9 Jan 2018 10:54:42 -0500 From: Jernej =?utf-8?B?xaBrcmFiZWM=?= To: Chen-Yu Tsai Cc: Maxime Ripard , David Airlie , Rob Herring , Mark Rutland , Archit Taneja , a.hajda@samsung.com, Laurent Pinchart , Mike Turquette , Stephen Boyd , Jose.Abreu@synopsys.com, Neil Armstrong , dri-devel , devicetree , linux-arm-kernel , linux-kernel , linux-clk , linux-sunxi Subject: Re: [linux-sunxi] Re: [PATCH 01/11] clk: sunxi-ng: Don't set k if width is 0 for nkmp plls Date: Tue, 09 Jan 2018 16:54:34 +0100 Message-ID: <1542502.H6M8hg3JYZ@jernej-laptop> In-Reply-To: References: <20171230210203.24115-1-jernej.skrabec@siol.net> <3625461.aU9oqMdpo3@jernej-laptop> MIME-Version: 1.0 Content-Transfer-Encoding: 8BIT Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Return-Path: Hi Chen-Yu, Dne ponedeljek, 08. januar 2018 ob 10:19:47 CET je Chen-Yu Tsai napisal(a): > On Fri, Jan 5, 2018 at 3:28 AM, Jernej Škrabec wrote: > > Hi, > > > > Dne četrtek, 04. januar 2018 ob 15:45:18 CET je Chen-Yu Tsai napisal(a): > >> On Sun, Dec 31, 2017 at 5:01 AM, Jernej Skrabec > > > > wrote: > >> > For example, A83T have nmp plls which are modelled as nkmp plls. Since > >> > k > >> > is not specified, it has offset 0, shift 0 and lowest value 1. This > >> > means that LSB bit is always set to 1, which may change clock rate. > >> > > >> > Fix that by applying k factor only if k width is greater than 0. > >> > > >> > Signed-off-by: Jernej Skrabec > >> > --- > >> > > >> > drivers/clk/sunxi-ng/ccu_nkmp.c | 21 +++++++++++++-------- > >> > 1 file changed, 13 insertions(+), 8 deletions(-) > >> > > >> > diff --git a/drivers/clk/sunxi-ng/ccu_nkmp.c > >> > b/drivers/clk/sunxi-ng/ccu_nkmp.c index e58c95787f94..709f528af2b3 > >> > 100644 > >> > --- a/drivers/clk/sunxi-ng/ccu_nkmp.c > >> > +++ b/drivers/clk/sunxi-ng/ccu_nkmp.c > >> > @@ -81,7 +81,7 @@ static unsigned long ccu_nkmp_recalc_rate(struct > >> > clk_hw > >> > *hw,> > >> > > >> > unsigned long parent_rate) > >> > > >> > { > >> > > >> > struct ccu_nkmp *nkmp = hw_to_ccu_nkmp(hw); > >> > > >> > - unsigned long n, m, k, p; > >> > + unsigned long n, m, k = 1, p; > >> > > >> > u32 reg; > >> > > >> > reg = readl(nkmp->common.base + nkmp->common.reg); > >> > > >> > @@ -92,11 +92,13 @@ static unsigned long ccu_nkmp_recalc_rate(struct > >> > clk_hw *hw,> > >> > > >> > if (!n) > >> > > >> > n++; > >> > > >> > - k = reg >> nkmp->k.shift; > >> > - k &= (1 << nkmp->k.width) - 1; > >> > - k += nkmp->k.offset; > >> > - if (!k) > >> > - k++; > >> > + if (nkmp->k.width) { > >> > + k = reg >> nkmp->k.shift; > >> > + k &= (1 << nkmp->k.width) - 1; > >> > + k += nkmp->k.offset; > >> > + if (!k) > >> > + k++; > >> > + } > >> > >> The conditional shouldn't be necessary. With nkmp->k.width = 0, > >> you'd simply get k & 0, which is 0, which then gets bumped up to 1, > >> unless k.offset > 1, which would be a bug. > >> > >> > m = reg >> nkmp->m.shift; > >> > m &= (1 << nkmp->m.width) - 1; > >> > > >> > @@ -153,12 +155,15 @@ static int ccu_nkmp_set_rate(struct clk_hw *hw, > >> > unsigned long rate,> > >> > > >> > reg = readl(nkmp->common.base + nkmp->common.reg); > >> > reg &= ~GENMASK(nkmp->n.width + nkmp->n.shift - 1, > >> > nkmp->n.shift); > >> > > >> > - reg &= ~GENMASK(nkmp->k.width + nkmp->k.shift - 1, > >> > nkmp->k.shift); > >> > + if (nkmp->k.width) > >> > + reg &= ~GENMASK(nkmp->k.width + nkmp->k.shift - 1, > >> > + nkmp->k.shift); > >> > > >> > reg &= ~GENMASK(nkmp->m.width + nkmp->m.shift - 1, > >> > nkmp->m.shift); > >> > reg &= ~GENMASK(nkmp->p.width + nkmp->p.shift - 1, > >> > nkmp->p.shift); > >> > > >> > reg |= (_nkmp.n - nkmp->n.offset) << nkmp->n.shift; > >> > > >> > - reg |= (_nkmp.k - nkmp->k.offset) << nkmp->k.shift; > >> > + if (nkmp->k.width) > >> > + reg |= (_nkmp.k - nkmp->k.offset) << nkmp->k.shift; > >> > >> I think a better way would be > >> > >> reg |= ((_nkmp.k - nkmp->k.offset) << nkmp->k.shift) & > >> > >> GENMASK(nkmp->k.width + nkmp->k.shift - 1, nkmp->k.shift); > >> > >> And do this for all the factors, not just k. This pattern is what > >> regmap_update_bits does, which seems much safer. I wonder what > >> GENMASK() with a negative value would do though... > > > > You're right, GENMASK(-1, 0) equals 0 (calculated by hand, not tested). > > This seems much more elegant solution. > > > > Semi-related question: All nmp PLLs have much wider N range than real nkmp > > PLLs. This causes integer overflow when using nkmp formula from datasheet. > > Usually, N is 1-256 for nmp PLLs, which means that for very high N > > factors, it overflows. This also causes issue that M factor is never > > higher than 1. > Sounds like we can't use u8 for storing the factors. At least the > intermediate values we use to calculate the rates. Only issue with u8 could be max field in struct ccu_mult_internal for K factor. But since it's not used, there is no issue. All intermediate variables in ccu_nkmp are wider. > > > I was wondering, if patch would be acceptable which would change this > > formula: > > > > RATE = (24MHz * N * K) / (M * P) > > > > to this: > > > > RATE ((24MHz / M) * N * K) / P > > > > I checked all M factors and are all in 1-4 or 1-2 range, which means it > > wouldn't have any impact for real nkmp PLLs when parent is 24 MHz clock > > which is probably always. > > > > What do you think? > > I think this is acceptable. M is normally the pre-divider, so this > actually fits how the hardware works, including possible rounding > errors. Ok, I'll add a patch for that in v2. Best regards, Jernej > > ChenYu > > > I discovered that when I tried to set A83T PLL_VIDEO to 346.5 MHz which is > > possible only when above formula is changed. > > > > Best regards, > > Jernej > > > >> ChenYu > >> > >> > reg |= (_nkmp.m - nkmp->m.offset) << nkmp->m.shift; > >> > reg |= ilog2(_nkmp.p) << nkmp->p.shift; > >> > > >> > -- > >> > 2.15.1 > > > > -- > > You received this message because you are subscribed to the Google Groups > > "linux-sunxi" group. To unsubscribe from this group and stop receiving > > emails from it, send an email to > > linux-sunxi+unsubscribe@googlegroups.com. For more options, visit > > https://groups.google.com/d/optout.