Re: [PATCH 2/2] power: supply: Add AC driver for Surface Aggregator Module

[Maximilian Luz <luzmaximilian@xxxxxxxxx>]

Hi,

On 4/5/21 5:47 PM, Sebastian Reichel wrote:
> Hi,
>
> On Tue, Mar 09, 2021 at 01:05:30AM +0100, Maximilian Luz wrote:
> > 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@xxxxxxxxx>
> > ---
> >
> > Note: This patch depends on the
> >
> >      platform/surface: Add Surface Aggregator device registry
> >
> > series. More specifically patch
> >
> >      platform/surface: Set up Surface Aggregator device registry
> >
> > The full series has been merged into the for-next branch of the
> > platform-drivers-x86 tree [1]. The commit in question can be found at
> > [2].
> >
> > [1]: https://git.kernel.org/pub/scm/linux/kernel/git/pdx86/platform-drivers-x86.git/log/?h=for-next
> > [2]: https://git.kernel.org/pub/scm/linux/kernel/git/pdx86/platform-drivers-x86.git/commit/?h=for-next&id=fc622b3d36e6d91330fb21506b9ad1e3206a4dde
> >
> > ---
> >   MAINTAINERS                            |   1 +
> >   drivers/power/supply/Kconfig           |  16 ++
> >   drivers/power/supply/Makefile          |   1 +
> >   drivers/power/supply/surface_charger.c | 296 +++++++++++++++++++++++++
> >   4 files changed, 314 insertions(+)
> >   create mode 100644 drivers/power/supply/surface_charger.c
> >
> > diff --git a/MAINTAINERS b/MAINTAINERS
> > index f44521abe8bf..d6651ba93997 100644
> > --- a/MAINTAINERS
> > +++ b/MAINTAINERS
> > @@ -11867,6 +11867,7 @@ L:	linux-pm@xxxxxxxxxxxxxxx
> >   L:	platform-driver-x86@xxxxxxxxxxxxxxx
> >   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@xxxxxxxxx>
> > diff --git a/drivers/power/supply/Kconfig b/drivers/power/supply/Kconfig
> > index cebeff10d543..91f7cf425ac9 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..fe484523a2c2
> > --- /dev/null
> > +++ b/drivers/power/supply/surface_charger.c
> > @@ -0,0 +1,296 @@
> > +// 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@xxxxxxxxx>
> > + */
> > +
> > +#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 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 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 void spwr_ac_destroy(struct spwr_ac_device *ac)
> > +{
> > +	mutex_destroy(&ac->lock);
>
> same as battery driver - use devm_add_action_or_reset or
> just drop it. It's not very useful at the end of remove().

Right, I'll drop that.

> > +}
>
> static char *battery_supplied_to[] = {
>      "BAT1",
>      "BAT2",
> };
>
> > +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 = 2;

Thanks, I'll add that.

> > +	ac->psy = power_supply_register(&ac->sdev->dev, &ac->psy_desc, &psy_cfg);
> > +	if (IS_ERR(ac->psy))
> > +		return PTR_ERR(ac->psy);
> > +
> > +	status = ssam_notifier_register(ac->sdev->ctrl, &ac->notif);
> > +	if (status)
> > +		power_supply_unregister(ac->psy);
> > +
> > +	return status;
> > +}
> > +
> > +static int spwr_ac_unregister(struct spwr_ac_device *ac)
> > +{
> > +	ssam_notifier_unregister(ac->sdev->ctrl, &ac->notif);
> > +	power_supply_unregister(ac->psy);
>
> This driver can also use devm_power_supply_register :)

I'll switch to that.
 
> > +	return 0;
> > +}
> > +
> > +
> > +/* -- 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;
> > +	int status;
> > +
> > +	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);
> > +
> > +	status = spwr_ac_register(ac);
> > +	if (status)
> > +		spwr_ac_destroy(ac);
> > +
> > +	return status;
> > +}
> > +
> > +static void surface_ac_remove(struct ssam_device *sdev)
> > +{
> > +	struct spwr_ac_device *ac = ssam_device_get_drvdata(sdev);
> > +
> > +	spwr_ac_unregister(ac);
> > +	spwr_ac_destroy(ac);
> > +}
> > +
> > +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@xxxxxxxxx>");
> > +MODULE_DESCRIPTION("AC driver for Surface System Aggregator Module");
> > +MODULE_LICENSE("GPL");
>
> Otherwise LGTM.
>
> Thanks,
>
> -- Sebastian

Thanks for the review!

I'll start working on v2 right away.

Regards,
Max