From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 57858C7EE45 for ; Mon, 12 Jun 2023 08:53:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234210AbjFLIxk (ORCPT ); Mon, 12 Jun 2023 04:53:40 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52510 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233781AbjFLIxJ (ORCPT ); Mon, 12 Jun 2023 04:53:09 -0400 Received: from mout-p-102.mailbox.org (mout-p-102.mailbox.org [80.241.56.152]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 18B5D2D4A; Mon, 12 Jun 2023 01:52:25 -0700 (PDT) Received: from smtp2.mailbox.org (smtp2.mailbox.org [10.196.197.2]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange ECDHE (P-384) server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by mout-p-102.mailbox.org (Postfix) with ESMTPS id 4Qfln22Rxvz9sd2; Mon, 12 Jun 2023 10:52:22 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oltmanns.dev; s=MBO0001; t=1686559942; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=T2MJ+F0cRREqc9apuK/Y9l5PP1ml/WVEL7uBUhsIOhM=; b=AmtNWOEeOV8ZGTDCiTA9+LwCqvaGtuLcptDiEO4rk8YyGtg4ZXTKSOsAUpCR9qekTdQyek bhcca/VR59O4e96l1MfnZbk6TS9tJiwAbWTRht1KBuqDTPw6Bk7BSCAgCDefpPpe5/MJBj MX5GsA2AwmKTTqi5nKpYm0lnuE6rvJ2IBLof1mGM/y27LJjbkIoLDJjR47YS79A07wkT7U fNCn3EeKZo7qjtwTc/cMMO4U+bPiNSHCJbR4QhCbwLBZmRvAWIfYwSNf1WMRKTGCkHSr1e wM60L/hxSSHXnNNCTp7fcK7DtoEbQlfOURqgG8JZUNRdmhJfDajQFZhVM2NHaA== References: <20230611090143.132257-1-frank@oltmanns.dev> <20230611090143.132257-2-frank@oltmanns.dev> From: Frank Oltmanns To: Frank Oltmanns Cc: Andre Przywara , Chen-Yu Tsai , Jernej Skrabec , Maxime Ripard , Michael Turquette , Roman Beranek , Samuel Holland , Stephen Boyd , linux-arm-kernel@lists.infradead.org, linux-clk@vger.kernel.org, linux-kernel@vger.kernel.org, linux-sunxi@lists.linux.dev Subject: Re: [PATCH v2 1/2] clk: sunxi-ng: nkm: consider alternative parent rates when finding rate In-reply-to: <20230611090143.132257-2-frank@oltmanns.dev> Date: Mon, 12 Jun 2023 10:51:52 +0200 Message-ID: <87edmh12s7.fsf@oltmanns.dev> MIME-Version: 1.0 Content-Type: text/plain Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi all, I just found in the Allwinner A64 User Manual V1.0, that there are additional constraints on the combinations for pll-mipi, that are not (and never were) enforced by by ccu_nkm. On 2023-06-11 at 11:01:42 +0200, Frank Oltmanns wrote: > In case the CLK_SET_RATE_PARENT flag is set, consider using a different > parent rate when determining a new rate. > > To find the best match for the requested rate, perform the following > steps for each NKM combination: > - calculate the optimal parent rate, > - find the best parent rate that the parent clock actually supports > - use that parent rate to calculate the effective rate. > > In case the clk does not support setting the parent rate, use the same > algorithm as before. > > Signed-off-by: Frank Oltmanns > --- > drivers/clk/sunxi-ng/ccu_nkm.c | 66 +++++++++++++++++++++++++++++----- > 1 file changed, 58 insertions(+), 8 deletions(-) > > diff --git a/drivers/clk/sunxi-ng/ccu_nkm.c b/drivers/clk/sunxi-ng/ccu_nkm.c > index a0978a50edae..c49d5879fe73 100644 > --- a/drivers/clk/sunxi-ng/ccu_nkm.c > +++ b/drivers/clk/sunxi-ng/ccu_nkm.c > @@ -6,6 +6,7 @@ > > #include > #include > +#include > > #include "ccu_gate.h" > #include "ccu_nkm.h" > @@ -16,10 +17,49 @@ struct _ccu_nkm { > unsigned long m, min_m, max_m; > }; > > -static unsigned long ccu_nkm_find_best(unsigned long parent, unsigned long rate, > - struct _ccu_nkm *nkm) > +static unsigned long optimal_parent_rate(unsigned long rate, unsigned long n, > + unsigned long k, unsigned long m) > { > - unsigned long best_rate = 0; > + unsigned long _rate, parent; > + > + // We must first try to find the desired parent rate that is rounded up, because there are > + // cases where truncating makes us miss the requested rate. > + // E.g. rate=449035712, n=11, k=3, m=16 > + // When truncating, we'd get parent=217714284 and calculating the rate from that would give > + // us 449035710. When rounding up, we get parent=217714285 which would give us the requested > + // rate of 449035712. > + parent = DIV_ROUND_UP(rate * m, n * k); > + > + // But there are other cases, where rounding up the parent gives us a too high rate. > + // Therefore, we need to check for this case and, if necessary, truncate the parent rate > + // instead of rounding up. > + _rate = parent * n * k / m; > + if (_rate > rate) > + parent = rate * m / (n * k); > + return parent; > +} > + > +/** > + * ccu_nkm_find_best - Find the best nkm combination for a given rate > + * > + * @parent: rate of parent clock. This is used either as an input or out parameter: > + * - In cases where the parent clock can be set, this parameter will be updated to contain > + * the optimal rate for the parent to achieve the best rate for the nkm clock. > + * - In cases where the parent clock can not be set, this parameter must contain the > + * current rate of the parent, which is used to determine the best combination of n, k, > + * and m. > + * @rate: requested rate. > + * @nkm: Input/output parameter that contains the clocks constraints on the n, k, m combinations and > + * is updated in this function to contain the resulting best n, k, m combination. > + * @parent_hw: parent clock. If set, this function assumes that the parent clock can be updated to a > + * rate that would be best to in order to get as close as possible to @rate. This > + * parameter must be set to NULL if this function shall not try to find the optimal > + * parent rate for the requested rate. > + */ > +static unsigned long ccu_nkm_find_best(unsigned long *parent, unsigned long rate, > + struct _ccu_nkm *nkm, struct clk_hw *parent_hw) > +{ > + unsigned long best_rate = 0, best_parent_rate = *parent, tmp_parent = *parent; > unsigned long best_n = 0, best_k = 0, best_m = 0; > unsigned long _n, _k, _m; > > @@ -28,12 +68,17 @@ static unsigned long ccu_nkm_find_best(unsigned long parent, unsigned long rate, > for (_m = nkm->min_m; _m <= nkm->max_m; _m++) { According to the manual M/N has to be <= 3. Therefore we need a different maximum value for the _m-for-loop: unsigned long max_m = min(3 * _n, nkm->max_m); for (_m = nkm->min_m; _m <= max_m; _m++) { I suggest that I add an optional member max_mn_ratio to the structs ccu_nkm and _ccu_nkm. Optional meaning: Ignore if 0. > unsigned long tmp_rate; > > - tmp_rate = parent * _n * _k / _m; > - > + if (parent_hw) { > + tmp_parent = optimal_parent_rate(rate, _n, _k, _m); > + tmp_parent = clk_hw_round_rate(parent_hw, tmp_parent); > + } Another constraint is PLL-VIDEO0 rate / M >= 24 MHz. Therefore we also need: if (tmp_parent < 24000000 * _m) continue; So, we need another optional member min_m_times_parent or, for shortness, maybe min_m_parent. I could use help finding a good name for this. I guess there needs to be a V3 of this patchset. :) Regards, Frank > + tmp_rate = tmp_parent * _n * _k / _m; > if (tmp_rate > rate) > continue; > + > if ((rate - tmp_rate) < (rate - best_rate)) { > best_rate = tmp_rate; > + best_parent_rate = tmp_parent; > best_n = _n; > best_k = _k; > best_m = _m; > @@ -46,6 +91,8 @@ static unsigned long ccu_nkm_find_best(unsigned long parent, unsigned long rate, > nkm->k = best_k; > nkm->m = best_m; > > + *parent = best_parent_rate; > + > return best_rate; > } > > @@ -106,7 +153,7 @@ static unsigned long ccu_nkm_recalc_rate(struct clk_hw *hw, > } > > static unsigned long ccu_nkm_round_rate(struct ccu_mux_internal *mux, > - struct clk_hw *hw, > + struct clk_hw *parent_hw, > unsigned long *parent_rate, > unsigned long rate, > void *data) > @@ -124,7 +171,10 @@ static unsigned long ccu_nkm_round_rate(struct ccu_mux_internal *mux, > if (nkm->common.features & CCU_FEATURE_FIXED_POSTDIV) > rate *= nkm->fixed_post_div; > > - rate = ccu_nkm_find_best(*parent_rate, rate, &_nkm); > + if (!clk_hw_can_set_rate_parent(&nkm->common.hw)) > + rate = ccu_nkm_find_best(parent_rate, rate, &_nkm, NULL); > + else > + rate = ccu_nkm_find_best(parent_rate, rate, &_nkm, parent_hw); > > if (nkm->common.features & CCU_FEATURE_FIXED_POSTDIV) > rate /= nkm->fixed_post_div; > @@ -159,7 +209,7 @@ static int ccu_nkm_set_rate(struct clk_hw *hw, unsigned long rate, > _nkm.min_m = 1; > _nkm.max_m = nkm->m.max ?: 1 << nkm->m.width; > > - ccu_nkm_find_best(parent_rate, rate, &_nkm); > + ccu_nkm_find_best(&parent_rate, rate, &_nkm, NULL); > > spin_lock_irqsave(nkm->common.lock, flags);