Re: [PATCH RESEND v3 3/5] clk: qcom: gdsc: Add set and get hwmode callbacks to switch GDSC mode

From: Jagadeesh Kona <quic_jkona@quicinc.com>
To: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>,
	Abel Vesa <abel.vesa@linaro.org>
Cc: "Rafael J. Wysocki" <rafael@kernel.org>,
	Kevin Hilman <khilman@kernel.org>,
	Ulf Hansson <ulf.hansson@linaro.org>, Pavel Machek <pavel@ucw.cz>,
	Len Brown <len.brown@intel.com>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Bjorn Andersson <andersson@kernel.org>,
	"Andy Gross" <agross@kernel.org>,
	Konrad Dybcio <konrad.dybcio@linaro.org>,
	"Michael Turquette" <mturquette@baylibre.com>,
	Stephen Boyd <sboyd@kernel.org>,
	Stanimir Varbanov <stanimir.k.varbanov@gmail.com>,
	Vikash Garodia <quic_vgarodia@quicinc.com>,
	Bryan O'Donoghue <bryan.odonoghue@linaro.org>,
	Mauro Carvalho Chehab <mchehab@kernel.org>,
	Taniya Das <tdas@qti.qualcomm.com>, <linux-pm@vger.kernel.org>,
	<linux-kernel@vger.kernel.org>, <linux-arm-msm@vger.kernel.org>,
	<linux-clk@vger.kernel.org>, <linux-media@vger.kernel.org>
Subject: Re: [PATCH RESEND v3 3/5] clk: qcom: gdsc: Add set and get hwmode callbacks to switch GDSC mode
Date: Fri, 10 Nov 2023 14:02:58 +0530	[thread overview]
Message-ID: <5b3315fe-f59b-cdf3-b980-a5a68bceb6a9@quicinc.com> (raw)
In-Reply-To: <CAA8EJpqTafxkXfAZXdTCat1VphvHUTTWe1TUjbpMvqta1Jf+Cw@mail.gmail.com>

On 11/2/2023 2:58 AM, Dmitry Baryshkov wrote:
> On Wed, 1 Nov 2023 at 11:06, Abel Vesa <abel.vesa@linaro.org> wrote:
>>
>> From: Jagadeesh Kona <quic_jkona@quicinc.com>
>>
>> Add support for set and get hwmode callbacks to switch the GDSC between
>> SW and HW modes. Currently, the GDSC is moved to HW control mode
>> using HW_CTRL flag and if this flag is present, GDSC is moved to HW
>> mode as part of GDSC enable itself. The intention is to keep the
>> HW_CTRL flag functionality as is, since many older chipsets still use
>> this flag.
>>
>> Introduce a new HW_CTRL_TRIGGER flag to switch the GDSC back and forth
>> between HW/SW modes dynamically at runtime. If HW_CTRL_TRIGGER flag is
>> present, register set_hwmode_dev callback to switch the GDSC mode which
>> can be invoked from consumer drivers using dev_pm_genpd_set_hwmode
>> function. Unlike HW_CTRL flag, HW_CTRL_TRIGGER won't move the GDSC to HW
>> control mode as part of GDSC enable itself, GDSC will be moved to HW
>> control mode only when consumer driver explicity calls
>> dev_pm_genpd_set_hwmode to switch to HW mode. Also add the
>> dev_pm_genpd_get_hwmode to allow the consumers to read the actual
>> HW/SW mode from hardware.
> 
> Can we add two new flags:
> - HW_CTRL_TRIGGER
> - DEFAULT_HW_TRIGGER
> 
> And then define HW_CTRL as HW_CTRL_TRIGGER | DEFAULT_HW_TRIGGER ?
> 
> This way older platforms will keep existing behaviour, but can
> gradually migrate to the new callbacks?
> 

Thanks Dmitry for your review,

The current usecases we have for GDSC's are either use the existing 
HW_CTRL flag to switch the GDSC to HW mode in gdsc_enable() and back to 
SW mode in gdsc_disable(). The second usecase is don't switch GDSC mode 
in gdsc_enable() & gdsc_disable() at all, and switch the GDSC mode only 
in new callbacks when consumers explicitly request it using 
dev_pm_genpd_set_hwmode(), this can be achieved using the new 
HW_CTRL_TRIGGER flag.

By defining HW_CTRL as HW_CTRL_TRIGGER | DEFAULT_HW_TRIGGER, it switches 
the GDSC mode both in enable & disable callbacks and in new callbacks as 
well. But we currently don't have any usecase that requires this behaviour.

Thanks,
Jagadeesh

>>
>> Signed-off-by: Jagadeesh Kona <quic_jkona@quicinc.com>
>> Signed-off-by: Abel Vesa <abel.vesa@linaro.org>
>> ---
>>   drivers/clk/qcom/gdsc.c | 32 ++++++++++++++++++++++++++++++++
>>   drivers/clk/qcom/gdsc.h |  1 +
>>   2 files changed, 33 insertions(+)
>>
>> diff --git a/drivers/clk/qcom/gdsc.c b/drivers/clk/qcom/gdsc.c
>> index 5358e28122ab..c763524cd5da 100644
>> --- a/drivers/clk/qcom/gdsc.c
>> +++ b/drivers/clk/qcom/gdsc.c
>> @@ -363,6 +363,34 @@ static int gdsc_disable(struct generic_pm_domain *domain)
>>          return 0;
>>   }
>>
>> +static int gdsc_set_hwmode(struct generic_pm_domain *domain, struct device *dev, bool mode)
>> +{
>> +       struct gdsc *sc = domain_to_gdsc(domain);
>> +
>> +       if (sc->rsupply && !regulator_is_enabled(sc->rsupply)) {
>> +               pr_err("Cannot set mode while parent is disabled\n");
>> +               return -EIO;
>> +       }
>> +
>> +       return gdsc_hwctrl(sc, mode);
>> +}
>> +
>> +static bool gdsc_get_hwmode(struct generic_pm_domain *domain, struct device *dev)
>> +{
>> +       struct gdsc *sc = domain_to_gdsc(domain);
>> +       u32 val;
>> +       int ret;
>> +
>> +       ret = regmap_read(sc->regmap, sc->gdscr, &val);
>> +       if (ret)
>> +               return ret;
>> +
>> +       if (val & HW_CONTROL_MASK)
>> +               return true;
>> +
>> +       return false;
>> +}
>> +
>>   static int gdsc_init(struct gdsc *sc)
>>   {
>>          u32 mask, val;
>> @@ -451,6 +479,10 @@ static int gdsc_init(struct gdsc *sc)
>>                  sc->pd.power_off = gdsc_disable;
>>          if (!sc->pd.power_on)
>>                  sc->pd.power_on = gdsc_enable;
>> +       if (sc->flags & HW_CTRL_TRIGGER) {
>> +               sc->pd.set_hwmode_dev = gdsc_set_hwmode;
>> +               sc->pd.get_hwmode_dev = gdsc_get_hwmode;
>> +       }
>>
>>          ret = pm_genpd_init(&sc->pd, NULL, !on);
>>          if (ret)
>> diff --git a/drivers/clk/qcom/gdsc.h b/drivers/clk/qcom/gdsc.h
>> index 803512688336..1e2779b823d1 100644
>> --- a/drivers/clk/qcom/gdsc.h
>> +++ b/drivers/clk/qcom/gdsc.h
>> @@ -67,6 +67,7 @@ struct gdsc {
>>   #define ALWAYS_ON      BIT(6)
>>   #define RETAIN_FF_ENABLE       BIT(7)
>>   #define NO_RET_PERIPH  BIT(8)
>> +#define HW_CTRL_TRIGGER        BIT(9)
>>          struct reset_controller_dev     *rcdev;
>>          unsigned int                    *resets;
>>          unsigned int                    reset_count;
>>
>> --
>> 2.34.1
>>
> 
> 