linux-kernel - Re: [PATCH v6 1/3] pmdomain: ti_sci: add per-device latency constraint management

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Message-ID: <20241210104735.dtzdhdds6l7yjvgk@lcpd911>
Date: Tue, 10 Dec 2024 16:17:35 +0530
From: Dhruva Gole <d-gole@...com>
To: Kevin Hilman <khilman@...libre.com>
CC: Ulf Hansson <ulf.hansson@...aro.org>, <linux-pm@...r.kernel.org>,
        Nishanth
 Menon <nm@...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 v6 1/3] pmdomain: ti_sci: add per-device latency
 constraint management

On Dec 06, 2024 at 14:12:50 -0800, Kevin Hilman 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.
> 
> Also note that the PM QoS framework uses usecs as the units for
> latency whereas the TI SCI firmware uses msecs, so a conversion is
> needed before passing to TI SCI.
> 
> Co-developed-by: Vibhore Vardhan <vibhore@...com>
> Signed-off-by: Vibhore Vardhan <vibhore@...com>
> Reviewed-by: Markus Schneider-Pargmann <msp@...libre.com>
> Reviewed-by: Ulf Hansson <ulf.hansson@...aro.org>
> Tested-by: Dhruva Gole <d-gole@...com>
> Signed-off-by: Kevin Hilman <khilman@...libre.com>
> ---
>  drivers/pmdomain/ti/ti_sci_pm_domains.c | 55 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 55 insertions(+)
> 
> diff --git a/drivers/pmdomain/ti/ti_sci_pm_domains.c b/drivers/pmdomain/ti/ti_sci_pm_domains.c
> index 0e4bd749d067309654307484c5bb98711bf06daf..963fe1901c959197d5d8b5d34fd8420dfb180087 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>

nit: Do we not need to sort these includes alphabetically?

>  #include <linux/soc/ti/ti_sci_protocol.h>
>  #include <dt-bindings/soc/ti,sci_pm_domain.h>
>  
> @@ -51,6 +53,32 @@ 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;
> +}
> +
> +#ifdef CONFIG_PM_SLEEP
> +static void ti_sci_pd_set_lat_constraint(struct device *dev, s32 val)
> +{
> +	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;
> +	u16 val_ms;
> +	int ret;
> +
> +	/* PM QoS latency unit is usecs, TI SCI uses msecs */
> +	val_ms = val / USEC_PER_MSEC;
> +	ret = ti_sci->ops.pm_ops.set_latency_constraint(ti_sci, val_ms, 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);
> +}
> +#endif
> +
>  /*
>   * ti_sci_pd_power_off(): genpd power down hook
>   * @domain: pointer to the powerdomain to power off
> @@ -79,6 +107,26 @@ static int ti_sci_pd_power_on(struct generic_pm_domain *domain)
>  		return ti_sci->ops.dev_ops.get_device(ti_sci, pd->idx);
>  }
>  
> +#ifdef CONFIG_PM_SLEEP
> +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;
> +}
> +#else
> +#define ti_sci_pd_suspend		NULL
> +#endif
> +
>  /*
>   * ti_sci_pd_xlate(): translation service for TI SCI genpds
>   * @genpdspec: DT identification data for the genpd
> @@ -182,6 +230,13 @@ static int ti_sci_pm_domain_probe(struct platform_device *pdev)
>  				pd->pd.flags |= GENPD_FLAG_ACTIVE_WAKEUP;
>  				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;

Rest looks good.
Reviewed-by: Dhruva Gole <d-gole@...com>

-- 
Best regards,
Dhruva Gole
Texas Instruments Incorporated