linux-kernel - Re: [PATCH v4] clk: allow reentrant calls into the clk framework

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: <CAPDyKFoHQK576H+zsW9ykzJT-gjc6=qeiRVi26THa_4dhNVRVw@mail.gmail.com>
Date:	Wed, 27 Mar 2013 11:03:21 +0100
From:	Ulf Hansson <ulf.hansson@...aro.org>
To:	Viresh Kumar <viresh.kumar@...aro.org>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Mike Turquette <mturquette@...aro.org>,
	linaro-kernel@...ts.linaro.org, patches@...aro.org,
	linux-kernel@...r.kernel.org,
	Laurent Pinchart <laurent.pinchart@...asonboard.com>,
	David Brown <davidb@...eaurora.org>,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v4] clk: allow reentrant calls into the clk framework

On 27 March 2013 10:55, Viresh Kumar <viresh.kumar@...aro.org> wrote:
> On 27 March 2013 15:10, Thomas Gleixner <tglx@...utronix.de> wrote:
>> On Wed, 27 Mar 2013, Mike Turquette wrote:
>>
>>> Reentrancy into the clock framework from the clk.h api is necessary
>>> for clocks that are prepared and unprepared via i2c_transfer (which
>>> includes many PMICs and discrete audio chips) as well as for several
>>> other use cases.
>>
>> That explanation sucks.
>>
>> Why does an i2c clock need reentrancy? Just because it's i2c or what?
>
> I am noway connected to this development but was just going through
> your mail and i think i might know the answer why is this required.
>
> Consider an example where an external chip has clock controller and has
> bits which can be programmed to enable/disable clock. And this chip is
> connected via spi/i2c to SoC.
>
> clk_prepare(peripheral on external chip)
>   -> i2c_xfer(to write to external chips register)
>       -> clk_enable(i2c controller)
>           ->controller-xfer-routine.. and finally we enable clk here...
>
>
> Sorry if i am on the wrong side :)

I agree with you Viresh. I guess Mike should update the commit message.

I would also like add another reason to why this is needed. For some
clks you would like to do pinctrl operations from a clk hw. But since
a pinctrl driver likely requires a clk to be prepared|enabled, we run
into a clk reentrant issue.

Kind regards
Ulf Hansson

>
> --
> viresh
> --
> 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/
--
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/