linux-kernel - Re: [PATCH v3] clk: Add PWM clock driver

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] [day] [month] [year] [list]

Date:	Fri, 12 Dec 2014 10:53:56 +0100
From:	Philipp Zabel <p.zabel@...gutronix.de>
To:	Janusz Użycki <j.uzycki@...roma.com.pl>
Cc:	Mike Turquette <mturquette@...aro.org>,
	Thierry Reding <thierry.reding@...il.com>,
	Rob Herring <robh+dt@...nel.org>,
	Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-pwm@...r.kernel.org
Subject: Re: [PATCH v3] clk: Add PWM clock driver

Hi Janusz,

Am Freitag, den 12.12.2014, 09:58 +0100 schrieb Janusz Użycki:
> Hi Philipp,
> 
> It moved .enable to .prepare which can sleep and it works
> without any bug.
> The dirty fix:
>   const struct clk_ops clk_pwm_ops = {
> -       .enable = clk_pwm_enable,
> -       .disable = clk_pwm_disable,
> +       .prepare = clk_pwm_enable,
> +       .unprepare = clk_pwm_disable,
>          .recalc_rate = clk_pwm_recalc_rate,
>   };
> 
> 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

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/