linux-kernel - Re: [PATCH v3 02/22] PM / devfreq: tegra30: Keep interrupt disabled while governor is stopped

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Message-ID: <17fe0599-b36e-31bc-4964-4b7cb77e1d64@gmail.com>
Date:   Fri, 28 Jun 2019 10:12:29 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     myungjoo.ham@...sung.com,
        Thierry Reding <thierry.reding@...il.com>,
        Kyungmin Park <kyungmin.park@...sung.com>,
        Chanwoo Choi <cw00.choi@...sung.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Tomeu Vizoso <tomeu.vizoso@...labora.com>
Cc:     "linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
        "linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 02/22] PM / devfreq: tegra30: Keep interrupt disabled
 while governor is stopped

28.06.2019 9:48, MyungJoo Ham пишет:
>> There is no real need to keep interrupt always-enabled, will be nicer
>> to keep it disabled while governor is inactive.
>>
>> Suggested-by: Thierry Reding <thierry.reding@...il.com>
>> Signed-off-by: Dmitry Osipenko <digetx@...il.com>
>> ---
>> drivers/devfreq/tegra30-devfreq.c | 43 ++++++++++++++++---------------
>> 1 file changed, 22 insertions(+), 21 deletions(-)
>>
>> diff --git a/drivers/devfreq/tegra30-devfreq.c b/drivers/devfreq/tegra30-devfreq.c
>> index a27300f40b0b..5e2b133babdd 100644
>> --- a/drivers/devfreq/tegra30-devfreq.c
>> +++ b/drivers/devfreq/tegra30-devfreq.c
> []
>> @@ -416,8 +417,6 @@ static void tegra_actmon_start(struct tegra_devfreq *tegra)
>> {
>> 	unsigned int i;
>>
>> -	disable_irq(tegra->irq);
>> -
>> 	actmon_writel(tegra, ACTMON_SAMPLING_PERIOD - 1,
>> 		      ACTMON_GLB_PERIOD_CTRL);
>>
> 
> I think this has nothing to do with
> "keep it disabled while governor is inactive."
> 
> And this looks dangerous because it disables the safety measure
> of disabling interrupt while you touch some looking-critical registers.
> Anyway, as I do not know the internals of Tegra SoC, I cannot sure.

Sorry, I'm not sure what do you mean .. Before this patch we were disabling the
interrupt on a start of programming hardware configuration, now we don't needed to
disable the interrupt because it is already in the disabled state at that moment
since we're now requesting interrupt in the *disabled* state during of the driver's
probe using IRQ_NOAUTOEN flag.