From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 6EDAE22F13; Thu, 29 Feb 2024 01:58:21 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1709171901; cv=none; b=Nzwn9DQccp2zTIfSUGPvlYLa9LhSNdtZPEqzcakfhMXkhW8y/EAtlamB1ZryIiBd3Rhy8b1Pzfxs+FsXr6Y1/yI+hOY/0EnmOkOsGGenRTgxBvheUcMw7fSFrYpR+zpJHsmtbZOveCYnMp/NFpRI0dctnFTuUrvkcVSjn8anSKk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1709171901; c=relaxed/simple; bh=J41cmZC7bQsegjax8yQD7VpQyLCqWbWDH7KNEl/+hnA=; h=Message-ID:Content-Type:MIME-Version:In-Reply-To:References: Subject:From:Cc:To:Date; b=fJcPiULOL6XtkqMIZYuliMpJLnoZBM68KYSEmWVt4oanbEx2tHgURsqltv9sw5pIqD3v7kV/0rl0llffcB4O+WL8PtD0v4mypy/GjGdmuFzQx0/aa3SP8VBz6u/mlotndiJu1kr36iNb4LNKisjaL7I3atHSBtGvNaQY1HSAlJ0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=ppqXCoRE; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="ppqXCoRE" Received: by smtp.kernel.org (Postfix) with ESMTPSA id CEE00C433F1; Thu, 29 Feb 2024 01:58:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1709171900; bh=J41cmZC7bQsegjax8yQD7VpQyLCqWbWDH7KNEl/+hnA=; h=In-Reply-To:References:Subject:From:Cc:To:Date:From; b=ppqXCoRECb8qXQoHJV/NedfjPoAvUrCzaLZWrdv36y63x9YACBjE83Eip0svG9PBf lngFZh81/sv5eDP0xqh+DP9e55gJN9nUSINtJ7SDCGddGHywnAG9VF9O9sfnwpDvc2 0DApIgUKBUF6iPHDCAtlJ1DK0gKip1voMF7pZ86nP9sOb7kjkWPfHqhxj77yh/sBOa 2q3EsdbMQVAEfZwDuQMVAuuZpDuJzOJC7kxaTC+BIP9+j/2B1z4PTHwh0CN0xmeuIJ TCfGVBP7w7kadNgohRjctolPlhaclQhNnuqOvYyBZN1Hfa5EWDb+GWJwCmuxqzHi7B 1OW1E2HfMn97A== Message-ID: <0db752d31016823ccd3799925255a74a.sboyd@kernel.org> Content-Type: text/plain; charset="utf-8" Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable In-Reply-To: <20240224-mux-v1-1-608cc704ef43@outlook.com> References: <20240224-mux-v1-1-608cc704ef43@outlook.com> Subject: Re: [PATCH RESEND] clk: set initial best mux parent to current parent when determining rate From: Stephen Boyd Cc: linux-clk@vger.kernel.org, linux-kernel@vger.kernel.org, Yang Xiwen To: Michael Turquette , Yang Xiwen via B4 Relay , forbidden405@outlook.com Date: Wed, 28 Feb 2024 17:58:18 -0800 User-Agent: alot/0.10 Quoting Yang Xiwen via B4 Relay (2024-02-23 09:18:52) > From: Yang Xiwen >=20 > Originally, the initial clock rate is hardcoded to 0, this can lead to > some problem when setting a very small rate with CLK_MUX_ROUND_NEAREST. Did you mean CLK_MUX_ROUND_CLOSEST? >=20 > For example, if the lowest possible rate privided by the mux is 1000Hz, s/privided/provided/ > setting a rate below 500Hz will fail, because no clock can provide a > better rate than the non-existant 0. But it should succeed with 1000Hz > being set. >=20 > Setting the initial best parent to current parent could solve this bug > very well. >=20 > Signed-off-by: Yang Xiwen > --- > This is actually a v2 of [1], but seems too simple to have a unittest. > It's tested in a mmc host driver. It's not too simple for a unittest. >=20 > [1]: https://lore.kernel.org/linux-clk/20230421-clk-v3-1-9ff79e7e7fed@out= look.com/ In that thread I asked you to please Cc Maxime. Please do that. > --- > drivers/clk/clk.c | 4 ++++ > 1 file changed, 4 insertions(+) >=20 > diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c > index 2253c154a824..d98cebd7ff03 100644 > --- a/drivers/clk/clk.c > +++ b/drivers/clk/clk.c > @@ -649,6 +649,10 @@ int clk_mux_determine_rate_flags(struct clk_hw *hw, > =20 > /* find the parent that can provide the fastest rate <=3D rate */ > num_parents =3D core->num_parents; > + if (core->parent) { > + best_parent =3D core->parent; > + best =3D clk_core_get_rate_nolock(best_parent); > + } Is the problem that we're not using abs_diff()? ----8<---- diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c index a3bc7fb90d0f..91023345595f 100644 --- a/drivers/clk/clk.c +++ b/drivers/clk/clk.c @@ -542,7 +542,7 @@ static bool mux_is_better_rate(unsigned long rate, unsi= gned long now, unsigned long best, unsigned long flags) { if (flags & CLK_MUX_ROUND_CLOSEST) - return abs(now - rate) < abs(best - rate); + return abs_diff(now, rate) < abs_diff(best, rate); =20 return now <=3D rate && now > best; }