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

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Message-Id: <20241206-lpm-v6-10-constraints-pmdomain-v6-1-833980158c68@baylibre.com>
Date: Fri, 06 Dec 2024 14:12:50 -0800
From: Kevin Hilman <khilman@...libre.com>
To: Ulf Hansson <ulf.hansson@...aro.org>, linux-pm@...r.kernel.org
Cc: Nishanth Menon <nm@...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, 
 Kevin Hilman <khilman@...libre.com>
Subject: [PATCH v6 1/3] pmdomain: ti_sci: add per-device latency constraint
 management

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>
 #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;
 
 				pm_genpd_init(&pd->pd, NULL, true);
 

-- 
2.46.2