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Date: Fri, 9 Jul 2021 13:54:20 -0500
From: Bjorn Andersson <bjorn.andersson@...aro.org>
To: Dmitry Baryshkov <dmitry.baryshkov@...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 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.
> + 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.
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
>
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