Messages in this thread | | | Date | Wed, 27 Mar 2013 11:03:21 +0100 | Subject | Re: [PATCH v4] clk: allow reentrant calls into the clk framework | From | Ulf Hansson <> |
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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
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