linux-kernel - Re: [PATCH 1/3] clk: qcom: gcc-msm8998: Mark hmss_dvm and lpass

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Date:   Fri, 30 Nov 2018 08:39:26 -0700
From:   Jeffrey Hugo <jhugo@...eaurora.org>
To:     Marc Gonzalez <marc.w.gonzalez@...e.fr>,
        Stephen Boyd <sboyd@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>
Cc:     Michael Turquette <mturquette@...libre.com>,
        Andy Gross <andy.gross@...aro.org>,
        David Brown <david.brown@...aro.org>,
        linux-arm-msm@...r.kernel.org, linux-soc@...r.kernel.org,
        linux-clk@...r.kernel.org, linux-kernel@...r.kernel.org,
        Amit Kucheria <amit.kucheria@...aro.org>
Subject: Re: [PATCH 1/3] clk: qcom: gcc-msm8998: Mark hmss_dvm and lpass_at
 critical

On 11/30/2018 2:23 AM, Marc Gonzalez wrote:
> On 30/11/2018 09:12, Stephen Boyd wrote:
> 
>> Quoting Bjorn Andersson (2018-11-29 23:24:20)
>>
>>> On Thu 29 Nov 23:05 PST 2018, Stephen Boyd wrote:
>>>
>>>> Quoting Bjorn Andersson (2018-11-29 22:52:57)
>>>>
>>>>> Keep the two clocks enabled, so that the platform passes
>>>>> clk_disable_unused().
>>>>>
>>>>> Signed-off-by: Bjorn Andersson <bjorn.andersson@...aro.org>
>>>>> ---
>>>>>   drivers/clk/qcom/gcc-msm8998.c | 2 ++
>>>>>   1 file changed, 2 insertions(+)
>>>>>
>>>>> diff --git a/drivers/clk/qcom/gcc-msm8998.c b/drivers/clk/qcom/gcc-msm8998.c
>>>>> index 9f0ae403d5f5..d89f8e7c2a59 100644
>>>>> --- a/drivers/clk/qcom/gcc-msm8998.c
>>>>> +++ b/drivers/clk/qcom/gcc-msm8998.c
>>>>> @@ -1972,6 +1972,7 @@ static struct clk_branch gcc_hmss_dvm_bus_clk = {
>>>>>                  .enable_mask = BIT(0),
>>>>>                  .hw.init = &(struct clk_init_data){
>>>>>                          .name = "gcc_hmss_dvm_bus_clk",
>>>>> +                       .flags = CLK_IS_CRITICAL,
>>>>
>>>> Please add a comment about why they're critical. This is a temporary
>>>> solution?
>>>
>>> Disabling them in clk_disable_unused() are bad, mkay...
>>
>> Ugh sad.
>>
>>> SDM845 marks the equivalent clocks as critical with a comment that they
>>> must be on for system operation... I'm uncertain what the exact purpose
>>> of these two clocks are, so I don't have a better explanation right now.
>>
>> Ok. But does any driver ever want to use it? It may make more sense to
>> just remove it entirely and not touch it.
> 
> FWIW, gcc_hmss_dvm_bus_clk is flagged "always on" downstream:
> https://source.codeaurora.org/quic/la/kernel/msm-4.4/tree/drivers/clk/msm/clock-gcc-8998.c?h=LE.UM.1.3.r3.25#n1715
> 
> 
> config REGULATOR_CPR3_HMSS
>          bool "CPR3 regulator for HMSS"
>          depends on OF
>          select REGULATOR_CPR3
>          help
>            This driver supports Qualcomm Technologies, Inc. HMSS application
>            processor specific features including memory array power mux (APM)
>            switching, two CPR3 threads which monitor the two HMSS clusters that
>            are both powered by a shared supply, and hardware closed-loop auto
>            voltage stepping.  This driver reads both initial voltage and CPR
>            target quotient values out of hardware fuses.
> 
> I wasn't able to find the meaning of the HMSS acronym via git grep, pdfgrep,
> or a web search. It should be forbidden to use an undefined acronyms in
> bindings documentation, IMHO.

HMSS = Hydra Monaco SubSystem

> 
> 
> I couldn't find gcc_lpass_at_clk in the downstream 4.4 kernel...
> LPASS = Low Power Audio Subsystem
> 
> Regards.
> 


-- 
Jeffrey Hugo
Qualcomm Datacenter Technologies as an affiliate of Qualcomm 
Technologies, Inc.
Qualcomm Technologies, Inc. is a member of the
Code Aurora Forum, a Linux Foundation Collaborative Project.