linux-kernel - Re: [PATCH v2 43/65] ASoC: tlv320aic32x4: Add a determine

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20221104155123.qomguvthehnogkdd@houat>
Date:   Fri, 4 Nov 2022 16:51:23 +0100
From:   Maxime Ripard <maxime@...no.tech>
To:     Mark Brown <broonie@...nel.org>
Cc:     Stephen Boyd <sboyd@...nel.org>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Chen-Yu Tsai <wens@...e.org>, Daniel Vetter <daniel@...ll.ch>,
        Nicolas Ferre <nicolas.ferre@...rochip.com>,
        Thierry Reding <thierry.reding@...il.com>,
        Jaroslav Kysela <perex@...ex.cz>,
        Shawn Guo <shawnguo@...nel.org>,
        Fabio Estevam <festevam@...il.com>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Claudiu Beznea <claudiu.beznea@...rochip.com>,
        Michael Turquette <mturquette@...libre.com>,
        Dinh Nguyen <dinguyen@...nel.org>,
        Paul Cercueil <paul@...pouillou.net>,
        Chunyan Zhang <zhang.lyra@...il.com>,
        Manivannan Sadhasivam <mani@...nel.org>,
        Andreas Färber <afaerber@...e.de>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Abel Vesa <abelvesa@...nel.org>,
        Charles Keepax <ckeepax@...nsource.cirrus.com>,
        Alessandro Zummo <a.zummo@...ertech.it>,
        Peter De Schrijver <pdeschrijver@...dia.com>,
        Orson Zhai <orsonzhai@...il.com>,
        Alexandre Torgue <alexandre.torgue@...s.st.com>,
        Prashant Gaikwad <pgaikwad@...dia.com>,
        Liam Girdwood <lgirdwood@...il.com>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        Samuel Holland <samuel@...lland.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Richard Fitzgerald <rf@...nsource.cirrus.com>,
        Vinod Koul <vkoul@...nel.org>,
        NXP Linux Team <linux-imx@....com>,
        Sekhar Nori <nsekhar@...com>,
        Kishon Vijay Abraham I <kishon@...nel.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        Takashi Iwai <tiwai@...e.com>,
        David Airlie <airlied@...il.com>,
        Luca Ceresoli <luca.ceresoli@...tlin.com>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        Baolin Wang <baolin.wang@...ux.alibaba.com>,
        David Lechner <david@...hnology.com>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        Max Filippov <jcmvbkbc@...il.com>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        linux-stm32@...md-mailman.stormreply.com,
        alsa-devel@...a-project.org, linux-mediatek@...ts.infradead.org,
        linux-phy@...ts.infradead.org, linux-mips@...r.kernel.org,
        linux-renesas-soc@...r.kernel.org,
        linux-actions@...ts.infradead.org, linux-clk@...r.kernel.org,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>,
        patches@...nsource.cirrus.com, linux-tegra@...r.kernel.org,
        linux-rtc@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-sunxi@...ts.linux.dev, linux-kernel@...r.kernel.org,
        dri-devel@...ts.freedesktop.org
Subject: Re: [PATCH v2 43/65] ASoC: tlv320aic32x4: Add a determine_rate hook

Hi Mark,

On Fri, Nov 04, 2022 at 03:44:53PM +0000, Mark Brown wrote:
> On Fri, Nov 04, 2022 at 02:18:00PM +0100, Maxime Ripard wrote:
> 
> > So, the set_parent hook is effectively unused, possibly because of an
> > oversight. However, it could also be an explicit decision by the
> > original author to avoid any reparenting but through an explicit call to
> > clk_set_parent().
> 
> > The latter case would be equivalent to setting the flag
> > CLK_SET_RATE_NO_REPARENT, together with setting our determine_rate hook
> > to __clk_mux_determine_rate(). Indeed, if no determine_rate
> > implementation is provided, clk_round_rate() (through
> > clk_core_round_rate_nolock()) will call itself on the parent if
> > CLK_SET_RATE_PARENT is set, and will not change the clock rate
> > otherwise. __clk_mux_determine_rate() has the exact same behavior when
> > CLK_SET_RATE_NO_REPARENT is set.
> 
> > And if it was an oversight, then we are at least explicit about our
> > behavior now and it can be further refined down the line.
> 
> Given that the current approach involves patching every single user to
> set a default implementation it feels like it might be more
> straightforward to just have the clock API use that implementation if
> none is defined - as you say there's already a flag to indicate the
> unusual case where there's a solid reason to prevent reparenting.  It
> feels like the resulting API is more straightforward.

That would be another solution indeed. The thing is, most places where
determine_rate is missing seems to be oversight, and the flag is missing
as well.

Just filling determine_rate if it's missing with
__clk_mux_determine_rate will possibly pick different parents, and I'm
fairly certain that this have never been tested on most platforms, and
will be completely broken. And I don't really want to play a game of
whack-a-mole adding that flag everywhere it turns out it's broken.

Maxime

Download attachment "signature.asc" of type "application/pgp-signature" (229 bytes)