power: supply: Add AC driver for Surface Aggregator Module

On newer Microsoft Surface models (specifically 7th-generation, i.e.
Surface Pro 7, Surface Book 3, Surface Laptop 3, and Surface Laptop Go),
battery and AC status/information is no longer handled via standard ACPI
devices, but instead directly via the Surface System Aggregator Module
(SSAM), i.e. the embedded controller on those devices.

While on previous generation models, AC status is also handled via SSAM,
an ACPI shim was present to translate the standard ACPI AC interface to
SSAM requests. The SSAM interface itself, which is modeled closely after
the ACPI interface, has not changed.

This commit introduces a new SSAM client device driver to support AC
status/information via the aforementioned interface on said Surface
models.
Signed-off-by: Maximilian Luz <luzmaximilian@gmail.com>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>

MAINTAINERS

@@ -11867,6 +11867,7 @@ L:	linux-pm@vger.kernel.org
 L:	platform-driver-x86@vger.kernel.org
 S:	Maintained
 F:	drivers/power/supply/surface_battery.c
+F:	drivers/power/supply/surface_charger.c
 
 MICROSOFT SURFACE GPE LID SUPPORT DRIVER
 M:	Maximilian Luz <luzmaximilian@gmail.com>

drivers/power/supply/Kconfig

@@ -817,4 +817,20 @@ config BATTERY_SURFACE
 	  Microsoft Surface devices, i.e. Surface Pro 7, Surface Laptop 3,
 	  Surface Book 3, and Surface Laptop Go.
 
+config CHARGER_SURFACE
+	tristate "AC driver for 7th-generation Microsoft Surface devices"
+	depends on SURFACE_AGGREGATOR_REGISTRY
+	help
+	  Driver for AC devices connected via/managed by the Surface System
+	  Aggregator Module (SSAM).
+
+	  This driver provides AC-information and -status support for Surface
+	  devices where said data is not exposed via the standard ACPI devices.
+	  On those models (7th-generation), AC-information is instead handled
+	  directly via a SSAM client device and this driver.
+
+	  Say M or Y here to include AC status support for 7th-generation
+	  Microsoft Surface devices, i.e. Surface Pro 7, Surface Laptop 3,
+	  Surface Book 3, and Surface Laptop Go.
+
 endif # POWER_SUPPLY

drivers/power/supply/Makefile

@@ -102,3 +102,4 @@ obj-$(CONFIG_CHARGER_WILCO)	+= wilco-charger.o
 obj-$(CONFIG_RN5T618_POWER)	+= rn5t618_power.o
 obj-$(CONFIG_BATTERY_ACER_A500)	+= acer_a500_battery.o
 obj-$(CONFIG_BATTERY_SURFACE)	+= surface_battery.o
+obj-$(CONFIG_CHARGER_SURFACE)	+= surface_charger.o

drivers/power/supply/surface_charger.c

+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * AC driver for 7th-generation Microsoft Surface devices via Surface System
+ * Aggregator Module (SSAM).
+ *
+ * Copyright (C) 2019-2021 Maximilian Luz <luzmaximilian@gmail.com>
+ */
+
+#include <asm/unaligned.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/power_supply.h>
+#include <linux/types.h>
+
+#include <linux/surface_aggregator/device.h>
+
+
+/* -- SAM interface. -------------------------------------------------------- */
+
+enum sam_event_cid_bat {
+	SAM_EVENT_CID_BAT_ADP   = 0x17,
+};
+
+enum sam_battery_sta {
+	SAM_BATTERY_STA_OK      = 0x0f,
+	SAM_BATTERY_STA_PRESENT	= 0x10,
+};
+
+/* Get battery status (_STA). */
+SSAM_DEFINE_SYNC_REQUEST_CL_R(ssam_bat_get_sta, __le32, {
+	.target_category = SSAM_SSH_TC_BAT,
+	.command_id      = 0x01,
+});
+
+/* Get platform power source for battery (_PSR / DPTF PSRC). */
+SSAM_DEFINE_SYNC_REQUEST_CL_R(ssam_bat_get_psrc, __le32, {
+	.target_category = SSAM_SSH_TC_BAT,
+	.command_id      = 0x0d,
+});
+
+
+/* -- Device structures. ---------------------------------------------------- */
+
+struct spwr_psy_properties {
+	const char *name;
+	struct ssam_event_registry registry;
+};
+
+struct spwr_ac_device {
+	struct ssam_device *sdev;
+
+	char name[32];
+	struct power_supply *psy;
+	struct power_supply_desc psy_desc;
+
+	struct ssam_event_notifier notif;
+
+	struct mutex lock;  /* Guards access to state below. */
+
+	__le32 state;
+};
+
+
+/* -- State management. ----------------------------------------------------- */
+
+static int spwr_ac_update_unlocked(struct spwr_ac_device *ac)
+{
+	u32 old = ac->state;
+	int status;
+
+	lockdep_assert_held(&ac->lock);
+
+	status = ssam_retry(ssam_bat_get_psrc, ac->sdev, &ac->state);
+	if (status < 0)
+		return status;
+
+	return old != ac->state;
+}
+
+static int spwr_ac_update(struct spwr_ac_device *ac)
+{
+	int status;
+
+	mutex_lock(&ac->lock);
+	status = spwr_ac_update_unlocked(ac);
+	mutex_unlock(&ac->lock);
+
+	return status;
+}
+
+static int spwr_ac_recheck(struct spwr_ac_device *ac)
+{
+	int status;
+
+	status = spwr_ac_update(ac);
+	if (status > 0)
+		power_supply_changed(ac->psy);
+
+	return status >= 0 ? 0 : status;
+}
+
+static u32 spwr_notify_ac(struct ssam_event_notifier *nf, const struct ssam_event *event)
+{
+	struct spwr_ac_device *ac;
+	int status;
+
+	ac = container_of(nf, struct spwr_ac_device, notif);
+
+	dev_dbg(&ac->sdev->dev, "power event (cid = %#04x, iid = %#04x, tid = %#04x)\n",
+		event->command_id, event->instance_id, event->target_id);
+
+	/*
+	 * Allow events of all targets/instances here. Global adapter status
+	 * seems to be handled via target=1 and instance=1, but events are
+	 * reported on all targets/instances in use.
+	 *
+	 * While it should be enough to just listen on 1/1, listen everywhere to
+	 * make sure we don't miss anything.
+	 */
+
+	switch (event->command_id) {
+	case SAM_EVENT_CID_BAT_ADP:
+		status = spwr_ac_recheck(ac);
+		return ssam_notifier_from_errno(status) | SSAM_NOTIF_HANDLED;
+
+	default:
+		return 0;
+	}
+}
+
+
+/* -- Properties. ----------------------------------------------------------- */
+
+static const enum power_supply_property spwr_ac_props[] = {
+	POWER_SUPPLY_PROP_ONLINE,
+};
+
+static int spwr_ac_get_property(struct power_supply *psy, enum power_supply_property psp,
+				union power_supply_propval *val)
+{
+	struct spwr_ac_device *ac = power_supply_get_drvdata(psy);
+	int status;
+
+	mutex_lock(&ac->lock);
+
+	status = spwr_ac_update_unlocked(ac);
+	if (status)
+		goto out;
+
+	switch (psp) {
+	case POWER_SUPPLY_PROP_ONLINE:
+		val->intval = !!le32_to_cpu(ac->state);
+		break;
+
+	default:
+		status = -EINVAL;
+		goto out;
+	}
+
+out:
+	mutex_unlock(&ac->lock);
+	return status;
+}
+
+
+/* -- Device setup. --------------------------------------------------------- */
+
+static char *battery_supplied_to[] = {
+	"BAT1",
+	"BAT2",
+};
+
+static void spwr_ac_init(struct spwr_ac_device *ac, struct ssam_device *sdev,
+			 struct ssam_event_registry registry, const char *name)
+{
+	mutex_init(&ac->lock);
+	strncpy(ac->name, name, ARRAY_SIZE(ac->name) - 1);
+
+	ac->sdev = sdev;
+
+	ac->notif.base.priority = 1;
+	ac->notif.base.fn = spwr_notify_ac;
+	ac->notif.event.reg = registry;
+	ac->notif.event.id.target_category = sdev->uid.category;
+	ac->notif.event.id.instance = 0;
+	ac->notif.event.mask = SSAM_EVENT_MASK_NONE;
+	ac->notif.event.flags = SSAM_EVENT_SEQUENCED;
+
+	ac->psy_desc.name = ac->name;
+	ac->psy_desc.type = POWER_SUPPLY_TYPE_MAINS;
+	ac->psy_desc.properties = spwr_ac_props;
+	ac->psy_desc.num_properties = ARRAY_SIZE(spwr_ac_props);
+	ac->psy_desc.get_property = spwr_ac_get_property;
+}
+
+static int spwr_ac_register(struct spwr_ac_device *ac)
+{
+	struct power_supply_config psy_cfg = {};
+	__le32 sta;
+	int status;
+
+	/* Make sure the device is there and functioning properly. */
+	status = ssam_retry(ssam_bat_get_sta, ac->sdev, &sta);
+	if (status)
+		return status;
+
+	if ((le32_to_cpu(sta) & SAM_BATTERY_STA_OK) != SAM_BATTERY_STA_OK)
+		return -ENODEV;
+
+	psy_cfg.drv_data = ac;
+	psy_cfg.supplied_to = battery_supplied_to;
+	psy_cfg.num_supplicants = ARRAY_SIZE(battery_supplied_to);
+
+	ac->psy = devm_power_supply_register(&ac->sdev->dev, &ac->psy_desc, &psy_cfg);
+	if (IS_ERR(ac->psy))
+		return PTR_ERR(ac->psy);
+
+	return ssam_notifier_register(ac->sdev->ctrl, &ac->notif);
+}
+
+
+/* -- Driver setup. --------------------------------------------------------- */
+
+static int __maybe_unused surface_ac_resume(struct device *dev)
+{
+	return spwr_ac_recheck(dev_get_drvdata(dev));
+}
+SIMPLE_DEV_PM_OPS(surface_ac_pm_ops, NULL, surface_ac_resume);
+
+static int surface_ac_probe(struct ssam_device *sdev)
+{
+	const struct spwr_psy_properties *p;
+	struct spwr_ac_device *ac;
+
+	p = ssam_device_get_match_data(sdev);
+	if (!p)
+		return -ENODEV;
+
+	ac = devm_kzalloc(&sdev->dev, sizeof(*ac), GFP_KERNEL);
+	if (!ac)
+		return -ENOMEM;
+
+	spwr_ac_init(ac, sdev, p->registry, p->name);
+	ssam_device_set_drvdata(sdev, ac);
+
+	return spwr_ac_register(ac);
+}
+
+static void surface_ac_remove(struct ssam_device *sdev)
+{
+	struct spwr_ac_device *ac = ssam_device_get_drvdata(sdev);
+
+	ssam_notifier_unregister(sdev->ctrl, &ac->notif);
+}
+
+static const struct spwr_psy_properties spwr_psy_props_adp1 = {
+	.name = "ADP1",
+	.registry = SSAM_EVENT_REGISTRY_SAM,
+};
+
+static const struct ssam_device_id surface_ac_match[] = {
+	{ SSAM_SDEV(BAT, 0x01, 0x01, 0x01), (unsigned long)&spwr_psy_props_adp1 },
+	{ },
+};
+MODULE_DEVICE_TABLE(ssam, surface_ac_match);
+
+static struct ssam_device_driver surface_ac_driver = {
+	.probe = surface_ac_probe,
+	.remove = surface_ac_remove,
+	.match_table = surface_ac_match,
+	.driver = {
+		.name = "surface_ac",
+		.pm = &surface_ac_pm_ops,
+		.probe_type = PROBE_PREFER_ASYNCHRONOUS,
+	},
+};
+module_ssam_device_driver(surface_ac_driver);
+
+MODULE_AUTHOR("Maximilian Luz <luzmaximilian@gmail.com>");
+MODULE_DESCRIPTION("AC driver for Surface System Aggregator Module");
+MODULE_LICENSE("GPL");