From: Stephen Boyd <sboyd@kernel.org>
To: Ciprian Costea <ciprianmarian.costea@oss.nxp.com>,
Marc Kleine-Budde <mkl@pengutronix.de>,
Maxime Ripard <mripard@kernel.org>
Cc: Vincent Mailhol <mailhol.vincent@wanadoo.fr>,
linux-can@vger.kernel.org, linux-kernel@vger.kernel.org,
NXP S32 Linux Team <s32@nxp.com>,
imx@lists.linux.dev, Christophe Lizzi <clizzi@redhat.com>,
Alberto Ruiz <aruizrui@redhat.com>,
Enric Balletbo <eballetb@redhat.com>,
Eric Chanudet <echanude@redhat.com>,
Ghennadi Procopciuc <ghennadi.procopciuc@nxp.com>,
Michael Turquette <mturquette@baylibre.com>,
linux-clk@vger.kernel.org, kernel@pengutronix.de
Subject: Re: [PATCH] can: flexcan: enable PER clock before obtaining its rate
Date: Mon, 14 Apr 2025 17:27:10 -0700 [thread overview]
Message-ID: <e4bd8e47aeab761e409121ac9bc19408@kernel.org> (raw)
In-Reply-To: <20250414-camouflaged-silver-dodo-d0c000-mkl@pengutronix.de>
Quoting Marc Kleine-Budde (2025-04-14 02:55:34)
> On 14.04.2025 10:36:46, Ciprian Costea wrote:
> > From: Ciprian Marian Costea <ciprianmarian.costea@oss.nxp.com>
> >
> > The FlexCan driver assumes that the frequency of the 'per' clock can be
> > obtained even on disabled clocks, which is not always true.
> >
> > According to 'clk_get_rate' documentation, it is only valid once the clock
> > source has been enabled.
>
> In commit bde8870cd8c3 ("clk: Clarify clk_get_rate() expectations")
> Maxime Ripard changed the documentation of the of the function in clk.c
> to say it's allowed. However clk.h states "This is only valid once the
> clock source has been enabled.".
>
> I've added the common clock maintainers to Cc.
>
> Which documentation is correct? Is the clk.h correct for archs not using
> the common clock framework?
>
I don't know what arches not using the common clk framework (CCF) do so
I can't comment there. If you want something to work on an architecture
that doesn't use the CCF then follow the header file, but in all
practical cases _some_ rate will be returned from clk_get_rate() and
we're not going to BUG_ON() or crash the system in the CCF
implementation for this case. Enabling the clk is good hygiene though,
so is it really a problem to enable it here?
next prev parent reply other threads:[~2025-04-15 0:27 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20250414073646.1473157-1-ciprianmarian.costea@oss.nxp.com>
2025-04-14 9:55 ` [PATCH] can: flexcan: enable PER clock before obtaining its rate Marc Kleine-Budde
2025-04-15 0:27 ` Stephen Boyd [this message]
2025-04-15 9:03 ` Marc Kleine-Budde
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