[v2,2/2] power: supply: Add AC driver for Surface Aggregator Module

diff --git a/MAINTAINERS b/MAINTAINERS
index e989beffde99..bfb0ac2b642f 100644
--- a/MAINTAINERS
+++ b/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>
diff --git a/drivers/power/supply/Kconfig b/drivers/power/supply/Kconfig
index 5b5054762194..e696364126f1 100644
--- a/drivers/power/supply/Kconfig
+++ b/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
diff --git a/drivers/power/supply/Makefile b/drivers/power/supply/Makefile
index 134041538d2c..a7309a3d1a47 100644
--- a/drivers/power/supply/Makefile
+++ b/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
diff --git a/drivers/power/supply/surface_charger.c b/drivers/power/supply/surface_charger.c
new file mode 100644
index 000000000000..c2dd7e604d14
--- /dev/null
+++ b/drivers/power/supply/surface_charger.c
@@ -0,0 +1,282 @@ 
+// 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");