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Date: Sat, 10 Jul 2021 01:10:34 +0300
From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To: Bjorn Andersson <bjorn.andersson@...aro.org>
Cc: Andy Gross <agross@...nel.org>, Rob Herring <robh+dt@...nel.org>,
Stephen Boyd <sboyd@...nel.org>,
Taniya Das <tdas@...eaurora.org>,
Jonathan Marek <jonathan@...ek.ca>,
Michael Turquette <mturquette@...libre.com>,
linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org,
linux-clk@...r.kernel.org,
Bryan O'Donoghue <bryan.odonoghue@...aro.org>,
Mark Brown <broonie@...nel.org>,
Ulf Hansson <ulf.hansson@...aro.org>,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 4/7] clk: qcom: gdsc: call runtime PM functions for the
provider device
On 09/07/2021 21:54, Bjorn Andersson wrote:
> On Fri 09 Jul 12:31 CDT 2021, Dmitry Baryshkov wrote:
>
>> In order to properly handle runtime PM status of the provider device,
>> call pm_runtime_get/pm_runtime_put on the clock controller device.
>>
>> Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
>> ---
>> drivers/clk/qcom/gdsc.c | 66 ++++++++++++++++++++++++++++++++++++++---
>> drivers/clk/qcom/gdsc.h | 2 ++
>> 2 files changed, 64 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/clk/qcom/gdsc.c b/drivers/clk/qcom/gdsc.c
>> index ccd36617d067..6bec31fccb09 100644
>> --- a/drivers/clk/qcom/gdsc.c
>> +++ b/drivers/clk/qcom/gdsc.c
>> @@ -11,6 +11,7 @@
>> #include <linux/kernel.h>
>> #include <linux/ktime.h>
>> #include <linux/pm_domain.h>
>> +#include <linux/pm_runtime.h>
>> #include <linux/regmap.h>
>> #include <linux/regulator/consumer.h>
>> #include <linux/reset-controller.h>
>> @@ -50,6 +51,30 @@ enum gdsc_status {
>> GDSC_ON
>> };
>>
>> +static int gdsc_pm_runtime_get(struct gdsc *sc)
>> +{
>> + int ret;
>> +
>> + if (!sc->rpm_dev)
>> + return 0;
>> +
>> + ret = pm_runtime_get_sync(sc->rpm_dev);
>> + if (ret < 0) {
>> + pm_runtime_put_noidle(sc->rpm_dev);
>> + return ret;
>> + }
>> +
>> + return 0;
>> +}
>> +
>> +static int gdsc_pm_runtime_put(struct gdsc *sc)
>> +{
>> + if (!sc->rpm_dev)
>> + return 0;
>> +
>> + return pm_runtime_put_sync(sc->rpm_dev);
>> +}
>> +
>> /* Returns 1 if GDSC status is status, 0 if not, and < 0 on error */
>> static int gdsc_check_status(struct gdsc *sc, enum gdsc_status status)
>> {
>> @@ -232,9 +257,8 @@ static void gdsc_retain_ff_on(struct gdsc *sc)
>> regmap_update_bits(sc->regmap, sc->gdscr, mask, mask);
>> }
>>
>> -static int gdsc_enable(struct generic_pm_domain *domain)
>> +static int _gdsc_enable(struct gdsc *sc)
>> {
>> - struct gdsc *sc = domain_to_gdsc(domain);
>> int ret;
>>
>> if (sc->pwrsts == PWRSTS_ON)
>> @@ -290,11 +314,28 @@ static int gdsc_enable(struct generic_pm_domain *domain)
>> return 0;
>> }
>>
>> -static int gdsc_disable(struct generic_pm_domain *domain)
>> +static int gdsc_enable(struct generic_pm_domain *domain)
>> {
>> struct gdsc *sc = domain_to_gdsc(domain);
>> int ret;
>>
>> + ret = gdsc_pm_runtime_get(sc);
>> + if (ret)
>> + return ret;
>> +
>> + ret = _gdsc_enable(sc);
>> + if (ret) {
>> + gdsc_pm_runtime_put(sc);
>
> I presume what you do here is to leave the pm_runtime state of dispcc
> active if we succeeded in enabling the gdsc. But the gdsc is a subdomain
> of the parent domain, so the framework should take case of its
> dependency.
>
> So the reason for gdsc_pm_runtime_get()/put() in this code path is so
> that you can access the dispcc registers, i.e. I think you should
> get()/put() regardless of the return value.
pm domain code will handle enabling MMCX, so this code is not required
strictly speaking. Ulf suggested adding it back, so I followed the
suggestion. Maybe I misunderstood his suggestion.
putting pm_runtime after gdsc_enable does not sound like a logical case.
However it would simplify code a bit. Let me try...
>
>> + return ret;
>> + }
>> +
>> + return 0;
>> +}
>> +
>> +static int _gdsc_disable(struct gdsc *sc)
>> +{
>> + int ret;
>> +
>> if (sc->pwrsts == PWRSTS_ON)
>> return gdsc_assert_reset(sc);
>>
>> @@ -329,6 +370,18 @@ static int gdsc_disable(struct generic_pm_domain *domain)
>> return 0;
>> }
>>
>> +static int gdsc_disable(struct generic_pm_domain *domain)
>> +{
>> + struct gdsc *sc = domain_to_gdsc(domain);
>> + int ret;
>> +
>
> If the gdsc is found to be on at initialization, the next operation that
> will happen is gdsc_disable() and as you didn't activate the pm_runtime
> state in gdsc_init() you would in theory get here with registers
> unaccessible.
>
> In practice though, the active gdsc should through the being a subdomain
> of the parent domain keep power on for you, so you won't notice this
> issue.
Nice catch.
>
> But as above, I think you should wrap _gdsc_disable() in a get()/put()
> pair.
>
>> + ret = _gdsc_disable(sc);
>> + if (ret)
>> + return ret;
>> +
>> + return gdsc_pm_runtime_put(sc);
>> +}
>> +
>> static int gdsc_init(struct gdsc *sc)
>> {
>> u32 mask, val;
>> @@ -425,6 +478,8 @@ int gdsc_register(struct gdsc_desc *desc,
>> for (i = 0; i < num; i++) {
>> if (!scs[i])
>> continue;
>> + if (pm_runtime_enabled(dev))
>> + scs[i]->rpm_dev = dev;
>> scs[i]->regmap = regmap;
>> scs[i]->rcdev = rcdev;
>> ret = gdsc_init(scs[i]);
>> @@ -486,7 +541,10 @@ void gdsc_unregister(struct gdsc_desc *desc)
>> */
>> int gdsc_gx_do_nothing_enable(struct generic_pm_domain *domain)
>> {
>> + struct gdsc *sc = domain_to_gdsc(domain);
>> +
>> /* Do nothing but give genpd the impression that we were successful */
>> - return 0;
>> + /* Get the runtime PM device only */
>> + return gdsc_pm_runtime_get(sc);
>
> Per above, if you let the framework deal with the gdsc's dependencies on
> the parent domain and you only get()/put() for the sake of dispcc then
> you don't need you don't need to do this to keep the subsequent
> gdsc_disable() in balance.
>
>> }
>> EXPORT_SYMBOL_GPL(gdsc_gx_do_nothing_enable);
>> diff --git a/drivers/clk/qcom/gdsc.h b/drivers/clk/qcom/gdsc.h
>> index 5bb396b344d1..a82982df0a55 100644
>> --- a/drivers/clk/qcom/gdsc.h
>> +++ b/drivers/clk/qcom/gdsc.h
>> @@ -25,6 +25,7 @@ struct reset_controller_dev;
>> * @resets: ids of resets associated with this gdsc
>> * @reset_count: number of @resets
>> * @rcdev: reset controller
>> + * @rpm_dev: runtime PM device
>> */
>> struct gdsc {
>> struct generic_pm_domain pd;
>> @@ -58,6 +59,7 @@ struct gdsc {
>>
>> const char *supply;
>> struct regulator *rsupply;
>> + struct device *rpm_dev;
>
> This isn't just the "runtime pm device", it's the device this gdsc is
> associated with. So "dev" sounds sufficient to me, but that requires
> that you have a separate bool rpm_enabled to remember if
> pm_runtime_enabled() was true during probe.
>
> So unless we need "dev" for something else this might be sufficient.
>
> Regards,
> Bjorn
>
>> };
>>
>> struct gdsc_desc {
>> --
>> 2.30.2
>>
--
With best wishes
Dmitry
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