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

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Message-Id: <20240819-lpm-v6-10-constraints-pmdomain-v2-1-461325a6008f@baylibre.com>
Date: Mon, 19 Aug 2024 17:00:11 -0700
From: Kevin Hilman <khilman@...libre.com>
To: Ulf Hansson <ulf.hansson@...aro.org>, linux-pm@...r.kernel.org
Cc: 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: [PATCH v2 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.

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;
+}
+
+static int 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;
+	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