From mboxrd@z Thu Jan  1 00:00:00 1970
From: Philipp Zabel <p.zabel-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org>
Subject: Re: [PATCH v3] clk: Add PWM clock driver
Date: Fri, 12 Dec 2014 10:53:56 +0100
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To: Janusz =?UTF-8?Q?U=C5=BCycki?= <j.uzycki-9tnw74Q4ehaHKKo6LODCOg@public.gmane.org>
Cc: Mike Turquette <mturquette-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>, Thierry Reding <thierry.reding-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>, Rob Herring <robh+dt-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>, Pawel Moll <pawel.moll-5wv7dgnIgG8@public.gmane.org>, Mark Rutland <mark.rutland-5wv7dgnIgG8@public.gmane.org>, Ian Campbell <ijc+devicetree-KcIKpvwj1kUDXYZnReoRVg@public.gmane.org>, Kumar Gala <galak-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org>, devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-pwm-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
List-Id: devicetree@vger.kernel.org

Hi Janusz,

Am Freitag, den 12.12.2014, 09:58 +0100 schrieb Janusz U=C5=BCycki:
> Hi Philipp,
>=20
> It moved .enable to .prepare which can sleep and it works
> without any bug.
> The dirty fix:
>   const struct clk_ops clk_pwm_ops =3D {
> -       .enable =3D clk_pwm_enable,
> -       .disable =3D clk_pwm_disable,
> +       .prepare =3D clk_pwm_enable,
> +       .unprepare =3D clk_pwm_disable,
>          .recalc_rate =3D clk_pwm_recalc_rate,
>   };
>=20
> What do you think about?

Thanks! Since the pwm API does not give any guarantees that
pwm_enable/disable may be called from atomic context, I think this
change is correct. The PWM documentation says:

   "Currently the PWM core does not enforce any locking to pwm_enable()=
,
    pwm_disable() and pwm_config(), so the calling context is currently
    driver specific. This is an issue derived from the former barebone
    API and should be fixed soon."

clk_enable should support reentrancy, but calling clk_prepare_enable
inside a clk_enable callback is not going to work.

regards
Philipp

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