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SubjectRe: [PATCH 2/2] power: supply: Add AC driver for Surface Aggregator Module
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Date
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@gmail.com>
>> ---
>>
>> 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@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 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@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 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@gmail.com>");
>> +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

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