lkml.org 
[lkml]   [2013]   [Mar]   [27]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
SubjectRe: [PATCH v4] clk: allow reentrant calls into the clk framework
From
On 27 March 2013 10:55, Viresh Kumar <viresh.kumar@linaro.org> wrote:
> On 27 March 2013 15:10, Thomas Gleixner <tglx@linutronix.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@vger.kernel.org
> More majordomo info at http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at http://www.tux.org/lkml/


\
 
 \ /
  Last update: 2013-03-27 11:41    [W:0.093 / U:0.136 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site