linux-kernel - Re: [RFC 06/12] Clk: qcom: support for dynamic updating the PLL

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Date:   Sun, 30 Jul 2017 19:27:53 +0530
From:   Abhishek Sahu <absahu@...eaurora.org>
To:     Stephen Boyd <sboyd@...eaurora.org>
Cc:     mturquette@...libre.com, andy.gross@...aro.org,
        david.brown@...aro.org, rnayak@...eaurora.org,
        linux-arm-msm@...r.kernel.org, linux-soc@...r.kernel.org,
        linux-clk@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC 06/12] Clk: qcom: support for dynamic updating the PLL

On 2017-07-29 00:04, Stephen Boyd wrote:
> On 07/27, Abhishek Sahu wrote:
>> Some of the Alpha PLL’s support dynamic update in which the
>> frequency can be changed dynamically without turning off the PLL.
>> 
>> This dynamic update requires the following sequence
>> 
>> 1. Write the desired values to pll_l_val and pll_alpha_val.
>> 2. Toggle pll_latch_input from low to high.
>> 3. Wait for pll_ack_latch to transition from low to high.
>>    The new L and alpha values have been latched. It make
>>    take some time for the PLL to fully settle with these
>>    new values.
>> 4. Pull pll_latch_input low.
>> 
>> Signed-off-by: Abhishek Sahu <absahu@...eaurora.org>
> 
> I think Rajendra has a similar patch that was sent. Is this the
> same? Can you please look on the list and find it and compare?

  Checked the list. Rajendra has two patches

  1. https://www.spinics.net/lists/linux-arm-msm/msg23349.html

  Yes my patch does the same thing with minor diffs.
  My patch checks PLL_UPDATE_BYPASS and handles both
  the cases. We can merge both the patches. I will check
  with Rajendra and will work on this merge.

  2. Following patch fixes different issue although flag name
     is common.

  https://patchwork.kernel.org/patch/9662917/

  Shall I include this patch in my patch series but not
  sure we can directly turn off the PLL inside the PLL
  set rate operation since it will turn the PLL off for
  all its users.

-- 
Abhishek Sahu