Message-ID: <7hv7z9ahlw.fsf@baylibre.com>
Date: Thu, 05 Sep 2024 14:57:47 -0700
From: Kevin Hilman <khilman@...libre.com>
To: Ulf Hansson <ulf.hansson@...aro.org>
Cc: linux-pm@...r.kernel.org, Nishanth Menon <nm@...com>, Vibhore Vardhan
 <vibhore@...com>, Dhruva Gole <d-gole@...com>, Akashdeep Kaur
 <a-kaur@...com>, Sebin Francis <sebin.francis@...com>, Markus
 Schneider-Pargmann <msp@...libre.com>,
 linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/3] pmdomain: ti_sci: add per-device latency
 constraint management

Ulf Hansson <ulf.hansson@...aro.org> writes:

> On Tue, 20 Aug 2024 at 02:00, Kevin Hilman <khilman@...libre.com> wrote:
>>
>> For each device in a TI SCI PM domain, check whether the device has
>> any resume latency constraints set via per-device PM QoS.  If
>> constraints are set, send them to DM via the new SCI constraints API.
>>
>> Checking for constraints happen for each device before system-wide
>> suspend (via ->suspend() hook.)
>>
>> An important detail here is that the PM domain driver inserts itself
>> into the path of both the ->suspend() and ->resume() hook path
>> of *all* devices in the PM domain.  This allows generic PM domain code
>> to handle the constraint management and communication with TI SCI.
>>
>> Further, this allows device drivers to use existing PM QoS APIs to
>> add/update constraints.
>>
>> DM firmware clears constraints during its resume, so Linux has
>> to check/update/send constraints each time system suspends.
>>
>> Co-developed-by: Vibhore Vardhan <vibhore@...com>
>> Signed-off-by: Vibhore Vardhan <vibhore@...com>
>> Signed-off-by: Kevin Hilman <khilman@...libre.com>
>> Signed-off-by: Dhruva Gole <d-gole@...com>
>> ---
>>  drivers/pmdomain/ti/ti_sci_pm_domains.c | 48 ++++++++++++++++++++++++++++++++++++++++++++++++
>>  1 file changed, 48 insertions(+)
>>
>> diff --git a/drivers/pmdomain/ti/ti_sci_pm_domains.c b/drivers/pmdomain/ti/ti_sci_pm_domains.c
>> index 1510d5ddae3d..963272fa387b 100644
>> --- a/drivers/pmdomain/ti/ti_sci_pm_domains.c
>> +++ b/drivers/pmdomain/ti/ti_sci_pm_domains.c
>> @@ -13,6 +13,8 @@
>>  #include <linux/platform_device.h>
>>  #include <linux/pm_domain.h>
>>  #include <linux/slab.h>
>> +#include <linux/pm_qos.h>
>> +#include <linux/pm_runtime.h>
>>  #include <linux/soc/ti/ti_sci_protocol.h>
>>  #include <dt-bindings/soc/ti,sci_pm_domain.h>
>>
>> @@ -51,6 +53,29 @@ struct ti_sci_pm_domain {
>>
>>  #define genpd_to_ti_sci_pd(gpd) container_of(gpd, struct ti_sci_pm_domain, pd)
>>
>> +static inline bool ti_sci_pd_is_valid_constraint(s32 val)
>> +{
>> +       return val != PM_QOS_RESUME_LATENCY_NO_CONSTRAINT;
>> +}
>
> Should we perhaps add a generic helper function for this? Seems like a
> similar check is done at other places in the kernel too.

Maybe, but I don't see a lot of this same usage under drivers/*.  But
I'll have a closer look for a follow-up patch that might be able to make
a common helper for this.

>> +
>> +static int ti_sci_pd_set_lat_constraint(struct device *dev, s32 val)
>> +{
>
> Looks like you may want to turn this into a static void rather than
> static int. At least the caller, below, doesn't care about the return
> value.

Yup, OK.

>> +       struct generic_pm_domain *genpd = pd_to_genpd(dev->pm_domain);
>> +       struct ti_sci_pm_domain *pd = genpd_to_ti_sci_pd(genpd);
>> +       const struct ti_sci_handle *ti_sci = pd->parent->ti_sci;
>> +       int ret;
>> +
>> +       ret = ti_sci->ops.pm_ops.set_latency_constraint(ti_sci, val, TISCI_MSG_CONSTRAINT_SET);
>> +       if (ret)
>> +               dev_err(dev, "ti_sci_pd: set latency constraint failed: ret=%d\n",
>> +                       ret);
>> +       else
>> +               dev_dbg(dev, "ti_sci_pd: ID:%d set latency constraint %d\n",
>> +                       pd->idx, val);
>> +
>> +       return ret;
>> +}
>> +
>>  /*
>>   * ti_sci_pd_power_off(): genpd power down hook
>>   * @domain: pointer to the powerdomain to power off
>> @@ -79,6 +104,22 @@ static int ti_sci_pd_power_on(struct generic_pm_domain *domain)
>>                 return ti_sci->ops.dev_ops.get_device(ti_sci, pd->idx);
>>  }
>>
>> +static int ti_sci_pd_suspend(struct device *dev)
>> +{
>> +       int ret;
>> +       s32 val;
>> +
>> +       ret = pm_generic_suspend(dev);
>> +       if (ret)
>> +               return ret;
>> +
>> +       val = dev_pm_qos_read_value(dev, DEV_PM_QOS_RESUME_LATENCY);
>> +       if (ti_sci_pd_is_valid_constraint(val))
>> +               ti_sci_pd_set_lat_constraint(dev, val);
>> +
>> +       return 0;
>> +}
>> +
>>  /*
>>   * ti_sci_pd_xlate(): translation service for TI SCI genpds
>>   * @genpdspec: DT identification data for the genpd
>> @@ -188,6 +229,13 @@ static int ti_sci_pm_domain_probe(struct platform_device *pdev)
>>                                 pd->pd.power_on = ti_sci_pd_power_on;
>>                                 pd->idx = args.args[0];
>>                                 pd->parent = pd_provider;
>> +                               /*
>> +                                * If SCI constraint functions are present, then firmware
>> +                                * supports the constraints API.
>> +                                */
>> +                               if (pd_provider->ti_sci->ops.pm_ops.set_device_constraint &&
>> +                                   pd_provider->ti_sci->ops.pm_ops.set_latency_constraint)
>> +                                       pd->pd.domain.ops.suspend = ti_sci_pd_suspend;
>>
>>                                 pm_genpd_init(&pd->pd, NULL, true);
>>
>>
>> --
>> 2.46.0
>>
>
> Other than the minor things above, this looks good to me.

Thanks for the review!   Will spin a v3 shortly.

Kevin

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