linux-kernel - Re: [PATCH v2 1/3] pmdomain: ti_sci: add per-device latency constraint management

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Message-ID: <CAPDyKFrCyvSLYh9DoC661M-2D33oU9x5tFOe+Oem04V5KfqG3A@mail.gmail.com>
Date: Thu, 5 Sep 2024 13:30:19 +0200
From: Ulf Hansson <ulf.hansson@...aro.org>
To: Kevin Hilman <khilman@...libre.com>
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

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.

> +
> +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.

> +       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.

Kind regards
Uffe